[RFC-v5] tcm_vhost: Initial merge for vhost level target fabric driver

From: Nicholas Bellinger <nab@linux-iscsi.org>

Hello KVM + QEMU folks,

This is -v5 of the in-flight tcm_vhost fabric driver for KVM host virtualized
target support using the in-kernel storage stack with for-3.6 code.

The changes since -v4 have been pretty minimal.  A new GET_ABI_VERSION ioctl
has been added as requested by Anthony & Co, and after some back <-> forth on
the lists we've decided upon a starting point of VHOST_SCSI_ABI_VERSION=0,
and vhost-scsi RFC userspace has been updated accordingly.

Along with that, a few handfuls of vq related error messages where converted
to use vq_err as requested by MST, along with some minor checkpatch fixes.

So this point everything required to run tcm_vhost from drivers/target +
drivers/vhost, and virtio-scsi LLD bugfix has been merged into v3.6-rc0 code.

Please have a look and let us know if there are any last-minute pre-merge
comments ahead of MST returning from holiday this weekend.

Thank you!

--nab

Changelog v4 -> v5:

  Expose ABI version via VHOST_SCSI_GET_ABI_VERSION + use Rev 0 as
  starting point for v3.6-rc code (Stefan + ALiguori + nab)
  Convert vhost_scsi_handle_vq() to vq_err() (nab + MST)
  Minor style fixes from checkpatch (nab)

Changelog v3 -> v4:

  Rename vhost_vring_target -> vhost_scsi_target (mst + nab)
  Use TRANSPORT_IQN_LEN in vhost_scsi_target->vhost_wwpn[] def (nab)
  Move back to drivers/vhost/, and just use drivers/vhost/Kconfig.tcm (mst)
  Move TCM_VHOST related ioctl defines from include/linux/vhost.h ->
  drivers/vhost/tcm_vhost.h as requested by MST (nab)
  Move Kbuild.tcm include from drivers/staging -> drivers/vhost/, and
  just use 'if STAGING' around 'source drivers/vhost/Kbuild.tcm'

Changelog v2 -> v3:

  Unlock on error in tcm_vhost_drop_nexus() (DanC)
  Fix strlen() doesn't count the terminator (DanC)
  Call kfree() on an error path (DanC)
  Convert tcm_vhost_write_pending to use target_execute_cmd (hch + nab)
  Fix another strlen() off by one in tcm_vhost_make_tport (DanC)
  Add option under drivers/staging/Kconfig, and move to drivers/vhost/tcm/
  as requested by MST (nab)

Changelog v1 -> v2:

  Fix tv_cmd completion -> release SGL memory leak (nab)
  Fix sparse warnings for static variable usage ((Fengguang Wu)
  Fix sparse warnings for min() typing + printk format specs (Fengguang Wu)
  Convert to cmwq submission for I/O dispatch (nab + hch)

Changelog v0 -> v1:

  Merge into single source + header file, and move to drivers/vhost/

Cc: Michael S. Tsirkin <mst@redhat.com>
Cc: Stefan Hajnoczi <stefanha@linux.vnet.ibm.com>
Cc: Anthony Liguori <aliguori@us.ibm.com>
Cc: Zhi Yong Wu <wuzhy@cn.ibm.com>
Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: Christoph Hellwig <hch@lst.de>
Cc: Hannes Reinecke <hare@suse.de>
Cc: Jens Axboe <axboe@kernel.dk>
Signed-off-by: Nicholas Bellinger <nab@linux-iscsi.org>
---
 drivers/vhost/Kconfig     |    3 +
 drivers/vhost/Kconfig.tcm |    6 +
 drivers/vhost/Makefile    |    2 +
 drivers/vhost/tcm_vhost.c | 1628 +++++++++++++++++++++++++++++++++++++++++++++
 drivers/vhost/tcm_vhost.h |  101 +++
 5 files changed, 1740 insertions(+), 0 deletions(-)
 create mode 100644 drivers/vhost/Kconfig.tcm
 create mode 100644 drivers/vhost/tcm_vhost.c
 create mode 100644 drivers/vhost/tcm_vhost.h

On Thu, Jul 26, 2012 at 11:43:20PM +0000, Nicholas A. Bellinger wrote:
> From: Nicholas Bellinger <nab@linux-iscsi.org>
> 
> Hello KVM + QEMU folks,
> 
> This is -v5 of the in-flight tcm_vhost fabric driver for KVM host virtualized
> target support using the in-kernel storage stack with for-3.6 code.
> 
> The changes since -v4 have been pretty minimal.  A new GET_ABI_VERSION ioctl
> has been added as requested by Anthony & Co, and after some back <-> forth on
> the lists we've decided upon a starting point of VHOST_SCSI_ABI_VERSION=0,
> and vhost-scsi RFC userspace has been updated accordingly.
> 
> Along with that, a few handfuls of vq related error messages where converted
> to use vq_err as requested by MST, along with some minor checkpatch fixes.
> 
> So this point everything required to run tcm_vhost from drivers/target +
> drivers/vhost, and virtio-scsi LLD bugfix has been merged into v3.6-rc0 code.
> 
> Please have a look and let us know if there are any last-minute pre-merge
> comments ahead of MST returning from holiday this weekend.
> 
> Thank you!
> 
> --nab

Acked-by: Michael S. Tsirkin <mst@redhat.com>

some comments below but can be fixed in-tree I think.

> Changelog v4 -> v5:
> 
>   Expose ABI version via VHOST_SCSI_GET_ABI_VERSION + use Rev 0 as
>   starting point for v3.6-rc code (Stefan + ALiguori + nab)
>   Convert vhost_scsi_handle_vq() to vq_err() (nab + MST)
>   Minor style fixes from checkpatch (nab)
> 
> Changelog v3 -> v4:
> 
>   Rename vhost_vring_target -> vhost_scsi_target (mst + nab)
>   Use TRANSPORT_IQN_LEN in vhost_scsi_target->vhost_wwpn[] def (nab)
>   Move back to drivers/vhost/, and just use drivers/vhost/Kconfig.tcm (mst)
>   Move TCM_VHOST related ioctl defines from include/linux/vhost.h ->
>   drivers/vhost/tcm_vhost.h as requested by MST (nab)
>   Move Kbuild.tcm include from drivers/staging -> drivers/vhost/, and
>   just use 'if STAGING' around 'source drivers/vhost/Kbuild.tcm'
> 
> Changelog v2 -> v3:
> 
>   Unlock on error in tcm_vhost_drop_nexus() (DanC)
>   Fix strlen() doesn't count the terminator (DanC)
>   Call kfree() on an error path (DanC)
>   Convert tcm_vhost_write_pending to use target_execute_cmd (hch + nab)
>   Fix another strlen() off by one in tcm_vhost_make_tport (DanC)
>   Add option under drivers/staging/Kconfig, and move to drivers/vhost/tcm/
>   as requested by MST (nab)
> 
> Changelog v1 -> v2:
> 
>   Fix tv_cmd completion -> release SGL memory leak (nab)
>   Fix sparse warnings for static variable usage ((Fengguang Wu)
>   Fix sparse warnings for min() typing + printk format specs (Fengguang Wu)
>   Convert to cmwq submission for I/O dispatch (nab + hch)
> 
> Changelog v0 -> v1:
> 
>   Merge into single source + header file, and move to drivers/vhost/
> 
> Cc: Michael S. Tsirkin <mst@redhat.com>
> Cc: Stefan Hajnoczi <stefanha@linux.vnet.ibm.com>
> Cc: Anthony Liguori <aliguori@us.ibm.com>
> Cc: Zhi Yong Wu <wuzhy@cn.ibm.com>
> Cc: Paolo Bonzini <pbonzini@redhat.com>
> Cc: Christoph Hellwig <hch@lst.de>
> Cc: Hannes Reinecke <hare@suse.de>
> Cc: Jens Axboe <axboe@kernel.dk>
> Signed-off-by: Nicholas Bellinger <nab@linux-iscsi.org>
> ---
>  drivers/vhost/Kconfig     |    3 +
>  drivers/vhost/Kconfig.tcm |    6 +
>  drivers/vhost/Makefile    |    2 +
>  drivers/vhost/tcm_vhost.c | 1628 +++++++++++++++++++++++++++++++++++++++++++++
>  drivers/vhost/tcm_vhost.h |  101 +++
>  5 files changed, 1740 insertions(+), 0 deletions(-)
>  create mode 100644 drivers/vhost/Kconfig.tcm
>  create mode 100644 drivers/vhost/tcm_vhost.c
>  create mode 100644 drivers/vhost/tcm_vhost.h
> 
> diff --git a/drivers/vhost/Kconfig b/drivers/vhost/Kconfig
> index e4e2fd1..202bba6 100644
> --- a/drivers/vhost/Kconfig
> +++ b/drivers/vhost/Kconfig
> @@ -9,3 +9,6 @@ config VHOST_NET
>  	  To compile this driver as a module, choose M here: the module will
>  	  be called vhost_net.
>  
> +if STAGING
> +source "drivers/vhost/Kconfig.tcm"
> +endif
> diff --git a/drivers/vhost/Kconfig.tcm b/drivers/vhost/Kconfig.tcm
> new file mode 100644
> index 0000000..a9c6f76
> --- /dev/null
> +++ b/drivers/vhost/Kconfig.tcm
> @@ -0,0 +1,6 @@
> +config TCM_VHOST
> +	tristate "TCM_VHOST fabric module (EXPERIMENTAL)"
> +	depends on TARGET_CORE && EVENTFD && EXPERIMENTAL && m
> +	default n
> +	---help---
> +	Say M here to enable the TCM_VHOST fabric module for use with virtio-scsi guests
> diff --git a/drivers/vhost/Makefile b/drivers/vhost/Makefile
> index 72dd020..a27b053 100644
> --- a/drivers/vhost/Makefile
> +++ b/drivers/vhost/Makefile
> @@ -1,2 +1,4 @@
>  obj-$(CONFIG_VHOST_NET) += vhost_net.o
>  vhost_net-y := vhost.o net.o
> +
> +obj-$(CONFIG_TCM_VHOST) += tcm_vhost.o
> diff --git a/drivers/vhost/tcm_vhost.c b/drivers/vhost/tcm_vhost.c
> new file mode 100644
> index 0000000..fb36654
> --- /dev/null
> +++ b/drivers/vhost/tcm_vhost.c
> @@ -0,0 +1,1628 @@
> +/*******************************************************************************
> + * Vhost kernel TCM fabric driver for virtio SCSI initiators
> + *
> + * (C) Copyright 2010-2012 RisingTide Systems LLC.
> + * (C) Copyright 2010-2012 IBM Corp.
> + *
> + * Licensed to the Linux Foundation under the General Public License (GPL) version 2.
> + *
> + * Authors: Nicholas A. Bellinger <nab@risingtidesystems.com>
> + *          Stefan Hajnoczi <stefanha@linux.vnet.ibm.com>
> + *
> + * This program is free software; you can redistribute it and/or modify
> + * it under the terms of the GNU General Public License as published by
> + * the Free Software Foundation; either version 2 of the License, or
> + * (at your option) any later version.
> + *
> + * This program is distributed in the hope that it will be useful,
> + * but WITHOUT ANY WARRANTY; without even the implied warranty of
> + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
> + * GNU General Public License for more details.
> + *
> + ****************************************************************************/
> +
> +#include <linux/module.h>
> +#include <linux/moduleparam.h>
> +#include <generated/utsrelease.h>
> +#include <linux/utsname.h>
> +#include <linux/init.h>
> +#include <linux/slab.h>
> +#include <linux/kthread.h>
> +#include <linux/types.h>
> +#include <linux/string.h>
> +#include <linux/configfs.h>
> +#include <linux/ctype.h>
> +#include <linux/compat.h>
> +#include <linux/eventfd.h>
> +#include <linux/vhost.h>
> +#include <linux/fs.h>
> +#include <linux/miscdevice.h>
> +#include <asm/unaligned.h>
> +#include <scsi/scsi.h>
> +#include <scsi/scsi_tcq.h>
> +#include <target/target_core_base.h>
> +#include <target/target_core_fabric.h>
> +#include <target/target_core_fabric_configfs.h>
> +#include <target/target_core_configfs.h>
> +#include <target/configfs_macros.h>
> +#include <linux/vhost.h>
> +#include <linux/virtio_net.h> /* TODO vhost.h currently depends on this */
> +#include <linux/virtio_scsi.h>
> +
> +#include "vhost.c"
> +#include "vhost.h"
> +#include "tcm_vhost.h"
> +
> +struct vhost_scsi {
> +	atomic_t vhost_ref_cnt;
> +	struct tcm_vhost_tpg *vs_tpg;

Would b enice to add a note on locking about this field.

> +	struct vhost_dev dev;
> +	struct vhost_virtqueue vqs[3];
> +
> +	struct vhost_work vs_completion_work; /* cmd completion work item */
> +	struct list_head vs_completion_list;  /* cmd completion queue */
> +	spinlock_t vs_completion_lock;        /* protects s_completion_list */
> +};
> +
> +/* Local pointer to allocated TCM configfs fabric module */
> +static struct target_fabric_configfs *tcm_vhost_fabric_configfs;
> +
> +static struct workqueue_struct *tcm_vhost_workqueue;
> +
> +/* Global spinlock to protect tcm_vhost TPG list for vhost IOCTL access */
> +static DEFINE_MUTEX(tcm_vhost_mutex);
> +static LIST_HEAD(tcm_vhost_list);
> +
> +static int tcm_vhost_check_true(struct se_portal_group *se_tpg)
> +{
> +	return 1;
> +}
> +
> +static int tcm_vhost_check_false(struct se_portal_group *se_tpg)
> +{
> +	return 0;
> +}
> +
> +static char *tcm_vhost_get_fabric_name(void)
> +{
> +	return "vhost";
> +}
> +
> +static u8 tcm_vhost_get_fabric_proto_ident(struct se_portal_group *se_tpg)
> +{
> +	struct tcm_vhost_tpg *tpg = container_of(se_tpg,
> +				struct tcm_vhost_tpg, se_tpg);
> +	struct tcm_vhost_tport *tport = tpg->tport;
> +
> +	switch (tport->tport_proto_id) {
> +	case SCSI_PROTOCOL_SAS:
> +		return sas_get_fabric_proto_ident(se_tpg);
> +	case SCSI_PROTOCOL_FCP:
> +		return fc_get_fabric_proto_ident(se_tpg);
> +	case SCSI_PROTOCOL_ISCSI:
> +		return iscsi_get_fabric_proto_ident(se_tpg);
> +	default:
> +		pr_err("Unknown tport_proto_id: 0x%02x, using"
> +			" SAS emulation\n", tport->tport_proto_id);
> +		break;
> +	}
> +
> +	return sas_get_fabric_proto_ident(se_tpg);
> +}
> +
> +static char *tcm_vhost_get_fabric_wwn(struct se_portal_group *se_tpg)
> +{
> +	struct tcm_vhost_tpg *tpg = container_of(se_tpg,
> +				struct tcm_vhost_tpg, se_tpg);
> +	struct tcm_vhost_tport *tport = tpg->tport;
> +
> +	return &tport->tport_name[0];
> +}
> +
> +static u16 tcm_vhost_get_tag(struct se_portal_group *se_tpg)
> +{
> +	struct tcm_vhost_tpg *tpg = container_of(se_tpg,
> +				struct tcm_vhost_tpg, se_tpg);
> +	return tpg->tport_tpgt;
> +}
> +
> +static u32 tcm_vhost_get_default_depth(struct se_portal_group *se_tpg)
> +{
> +	return 1;
> +}
> +
> +static u32 tcm_vhost_get_pr_transport_id(
> +	struct se_portal_group *se_tpg,
> +	struct se_node_acl *se_nacl,
> +	struct t10_pr_registration *pr_reg,
> +	int *format_code,
> +	unsigned char *buf)
> +{
> +	struct tcm_vhost_tpg *tpg = container_of(se_tpg,
> +				struct tcm_vhost_tpg, se_tpg);
> +	struct tcm_vhost_tport *tport = tpg->tport;
> +
> +	switch (tport->tport_proto_id) {
> +	case SCSI_PROTOCOL_SAS:
> +		return sas_get_pr_transport_id(se_tpg, se_nacl, pr_reg,
> +					format_code, buf);
> +	case SCSI_PROTOCOL_FCP:
> +		return fc_get_pr_transport_id(se_tpg, se_nacl, pr_reg,
> +					format_code, buf);
> +	case SCSI_PROTOCOL_ISCSI:
> +		return iscsi_get_pr_transport_id(se_tpg, se_nacl, pr_reg,
> +					format_code, buf);
> +	default:
> +		pr_err("Unknown tport_proto_id: 0x%02x, using"
> +			" SAS emulation\n", tport->tport_proto_id);
> +		break;
> +	}
> +
> +	return sas_get_pr_transport_id(se_tpg, se_nacl, pr_reg,
> +			format_code, buf);
> +}
> +
> +static u32 tcm_vhost_get_pr_transport_id_len(
> +	struct se_portal_group *se_tpg,
> +	struct se_node_acl *se_nacl,
> +	struct t10_pr_registration *pr_reg,
> +	int *format_code)
> +{
> +	struct tcm_vhost_tpg *tpg = container_of(se_tpg,
> +				struct tcm_vhost_tpg, se_tpg);
> +	struct tcm_vhost_tport *tport = tpg->tport;
> +
> +	switch (tport->tport_proto_id) {
> +	case SCSI_PROTOCOL_SAS:
> +		return sas_get_pr_transport_id_len(se_tpg, se_nacl, pr_reg,
> +					format_code);
> +	case SCSI_PROTOCOL_FCP:
> +		return fc_get_pr_transport_id_len(se_tpg, se_nacl, pr_reg,
> +					format_code);
> +	case SCSI_PROTOCOL_ISCSI:
> +		return iscsi_get_pr_transport_id_len(se_tpg, se_nacl, pr_reg,
> +					format_code);
> +	default:
> +		pr_err("Unknown tport_proto_id: 0x%02x, using"
> +			" SAS emulation\n", tport->tport_proto_id);
> +		break;
> +	}
> +
> +	return sas_get_pr_transport_id_len(se_tpg, se_nacl, pr_reg,
> +			format_code);
> +}
> +
> +static char *tcm_vhost_parse_pr_out_transport_id(
> +	struct se_portal_group *se_tpg,
> +	const char *buf,
> +	u32 *out_tid_len,
> +	char **port_nexus_ptr)
> +{
> +	struct tcm_vhost_tpg *tpg = container_of(se_tpg,
> +				struct tcm_vhost_tpg, se_tpg);
> +	struct tcm_vhost_tport *tport = tpg->tport;
> +
> +	switch (tport->tport_proto_id) {
> +	case SCSI_PROTOCOL_SAS:
> +		return sas_parse_pr_out_transport_id(se_tpg, buf, out_tid_len,
> +					port_nexus_ptr);
> +	case SCSI_PROTOCOL_FCP:
> +		return fc_parse_pr_out_transport_id(se_tpg, buf, out_tid_len,
> +					port_nexus_ptr);
> +	case SCSI_PROTOCOL_ISCSI:
> +		return iscsi_parse_pr_out_transport_id(se_tpg, buf, out_tid_len,
> +					port_nexus_ptr);
> +	default:
> +		pr_err("Unknown tport_proto_id: 0x%02x, using"
> +			" SAS emulation\n", tport->tport_proto_id);
> +		break;
> +	}
> +
> +	return sas_parse_pr_out_transport_id(se_tpg, buf, out_tid_len,
> +			port_nexus_ptr);
> +}
> +
> +static struct se_node_acl *tcm_vhost_alloc_fabric_acl(
> +	struct se_portal_group *se_tpg)
> +{
> +	struct tcm_vhost_nacl *nacl;
> +
> +	nacl = kzalloc(sizeof(struct tcm_vhost_nacl), GFP_KERNEL);
> +	if (!nacl) {
> +		pr_err("Unable to alocate struct tcm_vhost_nacl\n");
> +		return NULL;
> +	}
> +
> +	return &nacl->se_node_acl;
> +}
> +
> +static void tcm_vhost_release_fabric_acl(
> +	struct se_portal_group *se_tpg,
> +	struct se_node_acl *se_nacl)
> +{
> +	struct tcm_vhost_nacl *nacl = container_of(se_nacl,
> +			struct tcm_vhost_nacl, se_node_acl);
> +	kfree(nacl);
> +}
> +
> +static u32 tcm_vhost_tpg_get_inst_index(struct se_portal_group *se_tpg)
> +{
> +	return 1;
> +}
> +
> +static void tcm_vhost_release_cmd(struct se_cmd *se_cmd)
> +{
> +	return;
> +}
> +
> +static int tcm_vhost_shutdown_session(struct se_session *se_sess)
> +{
> +	return 0;
> +}
> +
> +static void tcm_vhost_close_session(struct se_session *se_sess)
> +{
> +	return;
> +}
> +
> +static u32 tcm_vhost_sess_get_index(struct se_session *se_sess)
> +{
> +	return 0;
> +}
> +
> +static int tcm_vhost_write_pending(struct se_cmd *se_cmd)
> +{
> +	/* Go ahead and process the write immediately */
> +	target_execute_cmd(se_cmd);
> +	return 0;
> +}
> +
> +static int tcm_vhost_write_pending_status(struct se_cmd *se_cmd)
> +{
> +	return 0;
> +}
> +
> +static void tcm_vhost_set_default_node_attrs(struct se_node_acl *nacl)
> +{
> +	return;
> +}
> +
> +static u32 tcm_vhost_get_task_tag(struct se_cmd *se_cmd)
> +{
> +	return 0;
> +}
> +
> +static int tcm_vhost_get_cmd_state(struct se_cmd *se_cmd)
> +{
> +	return 0;
> +}
> +
> +static void vhost_scsi_complete_cmd(struct tcm_vhost_cmd *);

can we reorder code to avoid forward declarations?

> +
> +static int tcm_vhost_queue_data_in(struct se_cmd *se_cmd)
> +{
> +	struct tcm_vhost_cmd *tv_cmd = container_of(se_cmd,
> +				struct tcm_vhost_cmd, tvc_se_cmd);
> +	vhost_scsi_complete_cmd(tv_cmd);
> +	return 0;
> +}
> +
> +static int tcm_vhost_queue_status(struct se_cmd *se_cmd)
> +{
> +	struct tcm_vhost_cmd *tv_cmd = container_of(se_cmd,
> +				struct tcm_vhost_cmd, tvc_se_cmd);
> +	vhost_scsi_complete_cmd(tv_cmd);
> +	return 0;
> +}
> +
> +static int tcm_vhost_queue_tm_rsp(struct se_cmd *se_cmd)
> +{
> +	return 0;
> +}
> +
> +static u16 tcm_vhost_set_fabric_sense_len(struct se_cmd *se_cmd,
> +	u32 sense_length)
> +{
> +	return 0;
> +}
> +
> +static u16 tcm_vhost_get_fabric_sense_len(void)
> +{
> +	return 0;
> +}
> +
> +static void vhost_scsi_free_cmd(struct tcm_vhost_cmd *tv_cmd)
> +{
> +	struct se_cmd *se_cmd = &tv_cmd->tvc_se_cmd;
> +
> +	/* TODO locking against target/backend threads? */
> +	transport_generic_free_cmd(se_cmd, 1);
> +
> +	if (tv_cmd->tvc_sgl_count) {
> +		u32 i;
> +		for (i = 0; i < tv_cmd->tvc_sgl_count; i++)
> +			put_page(sg_page(&tv_cmd->tvc_sgl[i]));
> +
> +		kfree(tv_cmd->tvc_sgl);
> +	}
> +
> +	kfree(tv_cmd);
> +}
> +
> +/* Dequeue a command from the completion list */
> +static struct tcm_vhost_cmd *vhost_scsi_get_cmd_from_completion(
> +	struct vhost_scsi *vs)
> +{
> +	struct tcm_vhost_cmd *tv_cmd = NULL;
> +
> +	spin_lock_bh(&vs->vs_completion_lock);
> +	if (list_empty(&vs->vs_completion_list)) {
> +		spin_unlock_bh(&vs->vs_completion_lock);
> +		return NULL;
> +	}
> +
> +	list_for_each_entry(tv_cmd, &vs->vs_completion_list,
> +			    tvc_completion_list) {
> +		list_del(&tv_cmd->tvc_completion_list);
> +		break;
> +	}
> +	spin_unlock_bh(&vs->vs_completion_lock);
> +	return tv_cmd;
> +}
> +
> +/* Fill in status and signal that we are done processing this command
> + *
> + * This is scheduled in the vhost work queue so we are called with the owner
> + * process mm and can access the vring.
> + */
> +static void vhost_scsi_complete_cmd_work(struct vhost_work *work)
> +{
> +	struct vhost_scsi *vs = container_of(work, struct vhost_scsi,
> +					vs_completion_work);
> +	struct tcm_vhost_cmd *tv_cmd;
> +
> +	while ((tv_cmd = vhost_scsi_get_cmd_from_completion(vs)) != NULL) {

I normally prefer while ((tv_cmd = vhost_scsi_get_cmd_from_completion(vs)))
without != NULL

> +		struct virtio_scsi_cmd_resp v_rsp;
> +		struct se_cmd *se_cmd = &tv_cmd->tvc_se_cmd;
> +		int ret;
> +
> +		pr_debug("%s tv_cmd %p resid %u status %#02x\n", __func__,
> +			tv_cmd, se_cmd->residual_count, se_cmd->scsi_status);
> +
> +		memset(&v_rsp, 0, sizeof(v_rsp));
> +		v_rsp.resid = se_cmd->residual_count;
> +		/* TODO is status_qualifier field needed? */
> +		v_rsp.status = se_cmd->scsi_status;
> +		v_rsp.sense_len = se_cmd->scsi_sense_length;
> +		memcpy(v_rsp.sense, tv_cmd->tvc_sense_buf,
> +		       v_rsp.sense_len);
> +		ret = copy_to_user(tv_cmd->tvc_resp, &v_rsp, sizeof(v_rsp));
> +		if (likely(ret == 0))
> +			vhost_add_used(&vs->vqs[2], tv_cmd->tvc_vq_desc, 0);
> +		else
> +			pr_err("Faulted on virtio_scsi_cmd_resp\n");
> +
> +		vhost_scsi_free_cmd(tv_cmd);
> +	}
> +
> +	vhost_signal(&vs->dev, &vs->vqs[2]);
> +}
> +
> +static void vhost_scsi_complete_cmd(struct tcm_vhost_cmd *tv_cmd)
> +{
> +	struct vhost_scsi *vs = tv_cmd->tvc_vhost;
> +
> +	pr_debug("%s tv_cmd %p\n", __func__, tv_cmd);

Is this doing something you can not already do with
tracing? If all these pr_debug messages are useful,
I think it's best to add a kconfig entry for them
so that they are off for people even if they build
debug kernels.

> +
> +	spin_lock_bh(&vs->vs_completion_lock);
> +	list_add_tail(&tv_cmd->tvc_completion_list, &vs->vs_completion_list);
> +	spin_unlock_bh(&vs->vs_completion_lock);
> +
> +	vhost_work_queue(&vs->dev, &vs->vs_completion_work);
> +}
> +
> +static struct tcm_vhost_cmd *vhost_scsi_allocate_cmd(
> +	struct tcm_vhost_tpg *tv_tpg,
> +	struct virtio_scsi_cmd_req *v_req,
> +	u32 exp_data_len,
> +	int data_direction)
> +{
> +	struct tcm_vhost_cmd *tv_cmd;
> +	struct tcm_vhost_nexus *tv_nexus;
> +	struct se_portal_group *se_tpg = &tv_tpg->se_tpg;
> +	struct se_session *se_sess;
> +	struct se_cmd *se_cmd;
> +	int sam_task_attr;
> +
> +	tv_nexus = tv_tpg->tpg_nexus;
> +	if (!tv_nexus) {
> +		pr_err("Unable to locate active struct tcm_vhost_nexus\n");
> +		return ERR_PTR(-EIO);
> +	}
> +	se_sess = tv_nexus->tvn_se_sess;
> +
> +	tv_cmd = kzalloc(sizeof(struct tcm_vhost_cmd), GFP_ATOMIC);
> +	if (!tv_cmd) {
> +		pr_err("Unable to allocate struct tcm_vhost_cmd\n");
> +		return ERR_PTR(-ENOMEM);
> +	}
> +	INIT_LIST_HEAD(&tv_cmd->tvc_completion_list);
> +	tv_cmd->tvc_tag = v_req->tag;
> +
> +	se_cmd = &tv_cmd->tvc_se_cmd;
> +	/*
> +	 * Locate the SAM Task Attr from virtio_scsi_cmd_req
> +	 */
> +	sam_task_attr = v_req->task_attr;
> +	/*
> +	 * Initialize struct se_cmd descriptor from TCM infrastructure
> +	 */
> +	transport_init_se_cmd(se_cmd, se_tpg->se_tpg_tfo, se_sess, exp_data_len,
> +				data_direction, sam_task_attr,
> +				&tv_cmd->tvc_sense_buf[0]);
> +
> +#if 0	/* FIXME: vhost_scsi_allocate_cmd() BIDI operation */
> +	if (bidi)
> +		se_cmd->se_cmd_flags |= SCF_BIDI;
> +#endif
> +	return tv_cmd;
> +}
> +
> +/*
> + * Map a user memory range into a scatterlist
> + *
> + * Returns the number of scatterlist entries used or -errno on error.
> + */
> +static int vhost_scsi_map_to_sgl(struct scatterlist *sgl,
> +	unsigned int sgl_count, void __user *ptr, size_t len, int write)
> +{
> +	struct scatterlist *sg = sgl;
> +	unsigned int npages = 0;
> +	int ret;
> +
> +	while (len > 0) {
> +		struct page *page;
> +		unsigned int offset = (uintptr_t)ptr & ~PAGE_MASK;
> +		unsigned int nbytes = min_t(unsigned int,
> +				PAGE_SIZE - offset, len);
> +
> +		if (npages == sgl_count) {
> +			ret = -ENOBUFS;
> +			goto err;
> +		}
> +
> +		ret = get_user_pages_fast((unsigned long)ptr, 1, write, &page);
> +		BUG_ON(ret == 0); /* we should either get our page or fail */
> +		if (ret < 0)
> +			goto err;
> +
> +		sg_set_page(sg, page, nbytes, offset);
> +		ptr += nbytes;
> +		len -= nbytes;
> +		sg++;
> +		npages++;
> +	}
> +	return npages;
> +
> +err:
> +	/* Put pages that we hold */
> +	for (sg = sgl; sg != &sgl[npages]; sg++)
> +		put_page(sg_page(sg));
> +	return ret;
> +}
> +
> +static int vhost_scsi_map_iov_to_sgl(struct tcm_vhost_cmd *tv_cmd,
> +	struct iovec *iov, unsigned int niov, int write)
> +{
> +	int ret;
> +	unsigned int i;
> +	u32 sgl_count;
> +	struct scatterlist *sg;
> +
> +	/*
> +	 * Find out how long sglist needs to be
> +	 */
> +	sgl_count = 0;
> +	for (i = 0; i < niov; i++) {
> +		sgl_count += (((uintptr_t)iov[i].iov_base + iov[i].iov_len +
> +				PAGE_SIZE - 1) >> PAGE_SHIFT) -
> +				((uintptr_t)iov[i].iov_base >> PAGE_SHIFT);
> +	}
> +	/* TODO overflow checking */
> +
> +	sg = kmalloc(sizeof(tv_cmd->tvc_sgl[0]) * sgl_count, GFP_ATOMIC);
> +	if (!sg)
> +		return -ENOMEM;
> +	pr_debug("%s sg %p sgl_count %u is_err %ld\n", __func__,
> +	       sg, sgl_count, IS_ERR(sg));
> +	sg_init_table(sg, sgl_count);
> +
> +	tv_cmd->tvc_sgl = sg;
> +	tv_cmd->tvc_sgl_count = sgl_count;
> +
> +	pr_debug("Mapping %u iovecs for %u pages\n", niov, sgl_count);
> +	for (i = 0; i < niov; i++) {
> +		ret = vhost_scsi_map_to_sgl(sg, sgl_count, iov[i].iov_base,
> +					iov[i].iov_len, write);
> +		if (ret < 0) {
> +			for (i = 0; i < tv_cmd->tvc_sgl_count; i++)
> +				put_page(sg_page(&tv_cmd->tvc_sgl[i]));
> +			kfree(tv_cmd->tvc_sgl);
> +			tv_cmd->tvc_sgl = NULL;
> +			tv_cmd->tvc_sgl_count = 0;
> +			return ret;
> +		}
> +
> +		sg += ret;
> +		sgl_count -= ret;
> +	}
> +	return 0;
> +}
> +
> +static void tcm_vhost_submission_work(struct work_struct *work)
> +{
> +	struct tcm_vhost_cmd *tv_cmd =
> +		container_of(work, struct tcm_vhost_cmd, work);
> +	struct se_cmd *se_cmd = &tv_cmd->tvc_se_cmd;
> +	struct scatterlist *sg_ptr, *sg_bidi_ptr = NULL;
> +	int rc, sg_no_bidi = 0;
> +	/*
> +	 * Locate the struct se_lun pointer based on v_req->lun, and
> +	 * attach it to struct se_cmd
> +	 */
> +	rc = transport_lookup_cmd_lun(&tv_cmd->tvc_se_cmd, tv_cmd->tvc_lun);
> +	if (rc < 0) {
> +		pr_err("Failed to look up lun: %d\n", tv_cmd->tvc_lun);
> +		transport_send_check_condition_and_sense(&tv_cmd->tvc_se_cmd,
> +			tv_cmd->tvc_se_cmd.scsi_sense_reason, 0);
> +		transport_generic_free_cmd(se_cmd, 0);
> +		return;
> +	}
> +
> +	rc = target_setup_cmd_from_cdb(se_cmd, tv_cmd->tvc_cdb);
> +	if (rc == -ENOMEM) {
> +		transport_send_check_condition_and_sense(se_cmd,
> +				TCM_LOGICAL_UNIT_COMMUNICATION_FAILURE, 0);
> +		transport_generic_free_cmd(se_cmd, 0);
> +		return;
> +	} else if (rc < 0) {
> +		if (se_cmd->se_cmd_flags & SCF_SCSI_RESERVATION_CONFLICT)
> +			tcm_vhost_queue_status(se_cmd);
> +		else
> +			transport_send_check_condition_and_sense(se_cmd,
> +					se_cmd->scsi_sense_reason, 0);
> +		transport_generic_free_cmd(se_cmd, 0);
> +		return;
> +	}
> +
> +	if (tv_cmd->tvc_sgl_count) {
> +		sg_ptr = tv_cmd->tvc_sgl;
> +		/*
> +		 * For BIDI commands, pass in the extra READ buffer
> +		 * to transport_generic_map_mem_to_cmd() below..
> +		 */
> +/* FIXME: Fix BIDI operation in tcm_vhost_submission_work() */
> +#if 0
> +		if (se_cmd->se_cmd_flags & SCF_BIDI) {
> +			sg_bidi_ptr = NULL;
> +			sg_no_bidi = 0;
> +		}
> +#endif
> +	} else {
> +		sg_ptr = NULL;
> +	}
> +
> +	rc = transport_generic_map_mem_to_cmd(se_cmd, sg_ptr,
> +				tv_cmd->tvc_sgl_count, sg_bidi_ptr,
> +				sg_no_bidi);
> +	if (rc < 0) {
> +		transport_send_check_condition_and_sense(se_cmd,
> +				se_cmd->scsi_sense_reason, 0);
> +		transport_generic_free_cmd(se_cmd, 0);
> +		return;
> +	}
> +	transport_handle_cdb_direct(se_cmd);
> +}
> +
> +static void vhost_scsi_handle_vq(struct vhost_scsi *vs)
> +{
> +	struct vhost_virtqueue *vq = &vs->vqs[2];
> +	struct virtio_scsi_cmd_req v_req;
> +	struct tcm_vhost_tpg *tv_tpg;
> +	struct tcm_vhost_cmd *tv_cmd;
> +	u32 exp_data_len, data_first, data_num, data_direction;
> +	unsigned out, in, i;
> +	int head, ret;
> +
> +	/* Must use ioctl VHOST_SCSI_SET_ENDPOINT */
> +	tv_tpg = vs->vs_tpg;
> +	if (unlikely(!tv_tpg)) {
> +		pr_err("%s endpoint not set\n", __func__);
> +		return;
> +	}
> +
> +	mutex_lock(&vq->mutex);
> +	vhost_disable_notify(&vs->dev, vq);
> +
> +	for (;;) {
> +		head = vhost_get_vq_desc(&vs->dev, vq, vq->iov,
> +					ARRAY_SIZE(vq->iov), &out, &in,
> +					NULL, NULL);
> +		pr_debug("vhost_get_vq_desc: head: %d, out: %u in: %u\n",
> +					head, out, in);
> +		/* On error, stop handling until the next kick. */
> +		if (unlikely(head < 0))
> +			break;
> +		/* Nothing new?  Wait for eventfd to tell us they refilled. */
> +		if (head == vq->num) {
> +			if (unlikely(vhost_enable_notify(&vs->dev, vq))) {
> +				vhost_disable_notify(&vs->dev, vq);
> +				continue;
> +			}
> +			break;
> +		}
> +
> +/* FIXME: BIDI operation */
> +		if (out == 1 && in == 1) {
> +			data_direction = DMA_NONE;
> +			data_first = 0;
> +			data_num = 0;
> +		} else if (out == 1 && in > 1) {
> +			data_direction = DMA_FROM_DEVICE;
> +			data_first = out + 1;
> +			data_num = in - 1;
> +		} else if (out > 1 && in == 1) {
> +			data_direction = DMA_TO_DEVICE;
> +			data_first = 1;
> +			data_num = out - 1;
> +		} else {
> +			vq_err(vq, "Invalid buffer layout out: %u in: %u\n",
> +					out, in);
> +			break;
> +		}
> +
> +		/*
> +		 * Check for a sane resp buffer so we can report errors to
> +		 * the guest.
> +		 */
> +		if (unlikely(vq->iov[out].iov_len !=
> +					sizeof(struct virtio_scsi_cmd_resp))) {
> +			vq_err(vq, "Expecting virtio_scsi_cmd_resp, got %zu"
> +				" bytes\n", vq->iov[out].iov_len);
> +			break;
> +		}
> +
> +		if (unlikely(vq->iov[0].iov_len != sizeof(v_req))) {
> +			vq_err(vq, "Expecting virtio_scsi_cmd_req, got %zu"
> +				" bytes\n", vq->iov[0].iov_len);
> +			break;
> +		}
> +		pr_debug("Calling __copy_from_user: vq->iov[0].iov_base: %p,"
> +			" len: %zu\n", vq->iov[0].iov_base, sizeof(v_req));
> +		ret = __copy_from_user(&v_req, vq->iov[0].iov_base,
> +				sizeof(v_req));
> +		if (unlikely(ret)) {
> +			vq_err(vq, "Faulted on virtio_scsi_cmd_req\n");
> +			break;
> +		}
> +
> +		exp_data_len = 0;
> +		for (i = 0; i < data_num; i++)
> +			exp_data_len += vq->iov[data_first + i].iov_len;
> +
> +		tv_cmd = vhost_scsi_allocate_cmd(tv_tpg, &v_req,
> +					exp_data_len, data_direction);
> +		if (IS_ERR(tv_cmd)) {
> +			vq_err(vq, "vhost_scsi_allocate_cmd failed %ld\n",
> +					PTR_ERR(tv_cmd));
> +			break;
> +		}
> +		pr_debug("Allocated tv_cmd: %p exp_data_len: %d, data_direction"
> +			": %d\n", tv_cmd, exp_data_len, data_direction);
> +
> +		tv_cmd->tvc_vhost = vs;
> +
> +		if (unlikely(vq->iov[out].iov_len !=
> +				sizeof(struct virtio_scsi_cmd_resp))) {
> +			vq_err(vq, "Expecting virtio_scsi_cmd_resp, got %zu"
> +				" bytes, out: %d, in: %d\n",
> +				vq->iov[out].iov_len, out, in);
> +			break;
> +		}
> +
> +		tv_cmd->tvc_resp = vq->iov[out].iov_base;
> +
> +		/*
> +		 * Copy in the recieved CDB descriptor into tv_cmd->tvc_cdb
> +		 * that will be used by tcm_vhost_new_cmd_map() and down into
> +		 * target_setup_cmd_from_cdb()
> +		 */
> +		memcpy(tv_cmd->tvc_cdb, v_req.cdb, TCM_VHOST_MAX_CDB_SIZE);
> +		/*
> +		 * Check that the recieved CDB size does not exceeded our
> +		 * hardcoded max for tcm_vhost
> +		 */
> +		/* TODO what if cdb was too small for varlen cdb header? */
> +		if (unlikely(scsi_command_size(tv_cmd->tvc_cdb) >
> +					TCM_VHOST_MAX_CDB_SIZE)) {
> +			vq_err(vq, "Received SCSI CDB with command_size: %d that"
> +				" exceeds SCSI_MAX_VARLEN_CDB_SIZE: %d\n",
> +				scsi_command_size(tv_cmd->tvc_cdb),
> +				TCM_VHOST_MAX_CDB_SIZE);
> +			break; /* TODO */
> +		}
> +		tv_cmd->tvc_lun = ((v_req.lun[2] << 8) | v_req.lun[3]) & 0x3FFF;
> +
> +		pr_debug("vhost_scsi got command opcode: %#02x, lun: %d\n",
> +			tv_cmd->tvc_cdb[0], tv_cmd->tvc_lun);
> +
> +		if (data_direction != DMA_NONE) {
> +			ret = vhost_scsi_map_iov_to_sgl(tv_cmd,
> +					&vq->iov[data_first], data_num,
> +					data_direction == DMA_TO_DEVICE);
> +			if (unlikely(ret)) {
> +				vq_err(vq, "Failed to map iov to sgl\n");
> +				break; /* TODO */
> +			}
> +		}
> +
> +		/*
> +		 * Save the descriptor from vhost_get_vq_desc() to be used to
> +		 * complete the virtio-scsi request in TCM callback context via
> +		 * tcm_vhost_queue_data_in() and tcm_vhost_queue_status()
> +		 */
> +		tv_cmd->tvc_vq_desc = head;
> +		/*
> +		 * Dispatch tv_cmd descriptor for cmwq execution in process
> +		 * context provided by tcm_vhost_workqueue.  This also ensures
> +		 * tv_cmd is executed on the same kworker CPU as this vhost
> +		 * thread to gain positive L2 cache locality effects..
> +		 */
> +		INIT_WORK(&tv_cmd->work, tcm_vhost_submission_work);
> +		queue_work(tcm_vhost_workqueue, &tv_cmd->work);
> +	}
> +
> +	mutex_unlock(&vq->mutex);
> +}
> +
> +static void vhost_scsi_ctl_handle_kick(struct vhost_work *work)
> +{
> +	pr_err("%s: The handling func for control queue.\n", __func__);
> +}
> +
> +static void vhost_scsi_evt_handle_kick(struct vhost_work *work)
> +{
> +	pr_err("%s: The handling func for event queue.\n", __func__);
> +}
> +

can userspace still trigger these? If not pls add a comment explaining
why are above never triggering.

> +static void vhost_scsi_handle_kick(struct vhost_work *work)
> +{
> +	struct vhost_virtqueue *vq = container_of(work, struct vhost_virtqueue,
> +						poll.work);
> +	struct vhost_scsi *vs = container_of(vq->dev, struct vhost_scsi, dev);
> +
> +	vhost_scsi_handle_vq(vs);
> +}
> +
> +/*
> + * Called from vhost_scsi_ioctl() context to walk the list of available
> + * tcm_vhost_tpg with an active struct tcm_vhost_nexus
> + */
> +static int vhost_scsi_set_endpoint(
> +	struct vhost_scsi *vs,
> +	struct vhost_scsi_target *t)
> +{
> +	struct tcm_vhost_tport *tv_tport;
> +	struct tcm_vhost_tpg *tv_tpg;
> +	int index;
> +
> +	mutex_lock(&vs->dev.mutex);
> +	/* Verify that ring has been setup correctly. */
> +	for (index = 0; index < vs->dev.nvqs; ++index) {
> +		/* Verify that ring has been setup correctly. */
> +		if (!vhost_vq_access_ok(&vs->vqs[index])) {
> +			mutex_unlock(&vs->dev.mutex);
> +			return -EFAULT;
> +		}
> +	}
> +
> +	if (vs->vs_tpg) {
> +		mutex_unlock(&vs->dev.mutex);
> +		return -EEXIST;
> +	}
> +	mutex_unlock(&vs->dev.mutex);

vs->vs_tpg can change at this point and be != NULL in loop below. Not an issue?

> +	mutex_lock(&tcm_vhost_mutex);
> +	list_for_each_entry(tv_tpg, &tcm_vhost_list, tv_tpg_list) {

If you move this loop to a function, then it can use goto to cleanup on error.

> +		mutex_lock(&tv_tpg->tv_tpg_mutex);
> +		if (!tv_tpg->tpg_nexus) {
> +			mutex_unlock(&tv_tpg->tv_tpg_mutex);
> +			continue;
> +		}
> +		if (atomic_read(&tv_tpg->tv_tpg_vhost_count)) {
> +			mutex_unlock(&tv_tpg->tv_tpg_mutex);
> +			continue;
> +		}
> +		tv_tport = tv_tpg->tport;
> +
> +		if (!strcmp(tv_tport->tport_name, t->vhost_wwpn) &&
> +		    (tv_tpg->tport_tpgt == t->vhost_tpgt)) {
> +			atomic_inc(&tv_tpg->tv_tpg_vhost_count);
> +			smp_mb__after_atomic_inc();

this an other uses of memory barriers need a comment: what are we
flushing out and why.  Also - could something like kref be used for
reference counting? If this is not datapath this might be better.

> +			mutex_unlock(&tv_tpg->tv_tpg_mutex);
> +			mutex_unlock(&tcm_vhost_mutex);
> +
> +			mutex_lock(&vs->dev.mutex);
> +			vs->vs_tpg = tv_tpg;
> +			atomic_inc(&vs->vhost_ref_cnt);
> +			smp_mb__after_atomic_inc();
> +			mutex_unlock(&vs->dev.mutex);
> +			return 0;
> +		}
> +		mutex_unlock(&tv_tpg->tv_tpg_mutex);
> +	}
> +	mutex_unlock(&tcm_vhost_mutex);
> +	return -EINVAL;
> +}
> +
> +static int vhost_scsi_clear_endpoint(
> +	struct vhost_scsi *vs,
> +	struct vhost_scsi_target *t)
> +{
> +	struct tcm_vhost_tport *tv_tport;
> +	struct tcm_vhost_tpg *tv_tpg;
> +	int index;
> +
> +	mutex_lock(&vs->dev.mutex);
> +	/* Verify that ring has been setup correctly. */
> +	for (index = 0; index < vs->dev.nvqs; ++index) {
> +		if (!vhost_vq_access_ok(&vs->vqs[index])) {
> +			mutex_unlock(&vs->dev.mutex);
> +			return -EFAULT;
> +		}
> +	}
> +
> +	if (!vs->vs_tpg) {
> +		mutex_unlock(&vs->dev.mutex);
> +		return -ENODEV;
> +	}
> +	tv_tpg = vs->vs_tpg;
> +	tv_tport = tv_tpg->tport;
> +
> +	if (strcmp(tv_tport->tport_name, t->vhost_wwpn) ||
> +	    (tv_tpg->tport_tpgt != t->vhost_tpgt)) {
> +		mutex_unlock(&vs->dev.mutex);
> +		pr_warn("tv_tport->tport_name: %s, tv_tpg->tport_tpgt: %hu"
> +			" does not match t->vhost_wwpn: %s, t->vhost_tpgt: %hu\n",
> +			tv_tport->tport_name, tv_tpg->tport_tpgt,
> +			t->vhost_wwpn, t->vhost_tpgt);
> +		return -EINVAL;
> +	}
> +	atomic_dec(&tv_tpg->tv_tpg_vhost_count);
> +	vs->vs_tpg = NULL;
> +	mutex_unlock(&vs->dev.mutex);
> +
> +	return 0;

We could do it like this:

	err:
		mutex_unlock(&vs->dev.mutex);
		return ret;

to make it clear we do not exit this with lock taken

> +}
> +
> +static int vhost_scsi_open(struct inode *inode, struct file *f)
> +{
> +	struct vhost_scsi *s;
> +	int r;
> +
> +	s = kzalloc(sizeof(*s), GFP_KERNEL);
> +	if (!s)
> +		return -ENOMEM;
> +
> +	vhost_work_init(&s->vs_completion_work, vhost_scsi_complete_cmd_work);
> +	INIT_LIST_HEAD(&s->vs_completion_list);
> +	spin_lock_init(&s->vs_completion_lock);
> +
> +	s->vqs[0].handle_kick = vhost_scsi_ctl_handle_kick;
> +	s->vqs[1].handle_kick = vhost_scsi_evt_handle_kick;
> +	s->vqs[2].handle_kick = vhost_scsi_handle_kick;

better to add an enum with VQ numbers.

> +	r = vhost_dev_init(&s->dev, s->vqs, 3);
> +	if (r < 0) {
> +		kfree(s);
> +		return r;
> +	}
> +
> +	f->private_data = s;
> +	return 0;
> +}
> +
> +static int vhost_scsi_release(struct inode *inode, struct file *f)
> +{
> +	struct vhost_scsi *s = f->private_data;
> +
> +	if (s->vs_tpg && s->vs_tpg->tport) {
> +		struct vhost_scsi_target backend;
> +
> +		memcpy(backend.vhost_wwpn, s->vs_tpg->tport->tport_name,
> +				sizeof(backend.vhost_wwpn));
> +		backend.vhost_tpgt = s->vs_tpg->tport_tpgt;
> +		vhost_scsi_clear_endpoint(s, &backend);
> +	}
> +
> +	vhost_dev_cleanup(&s->dev, false);
> +	kfree(s);
> +	return 0;
> +}
> +
> +static int vhost_scsi_set_features(struct vhost_scsi *vs, u64 features)
> +{
> +	if (features & ~VHOST_FEATURES)
> +		return -EOPNOTSUPP;
> +
> +	mutex_lock(&vs->dev.mutex);
> +	if ((features & (1 << VHOST_F_LOG_ALL)) &&
> +	    !vhost_log_access_ok(&vs->dev)) {
> +		mutex_unlock(&vs->dev.mutex);
> +		return -EFAULT;
> +	}
> +	vs->dev.acked_features = features;
> +	/* TODO possibly smp_wmb() and flush vqs */

Either that or fail if already running.
Current userspace does not change features once set,
but it's cleaner not to make assumptions.

> +	mutex_unlock(&vs->dev.mutex);
> +	return 0;
> +}
> +
> +static long vhost_scsi_ioctl(struct file *f, unsigned int ioctl,
> +				unsigned long arg)
> +{
> +	struct vhost_scsi *vs = f->private_data;
> +	struct vhost_scsi_target backend;
> +	void __user *argp = (void __user *)arg;
> +	u64 __user *featurep = argp;
> +	u64 features;
> +	int r;
> +
> +	switch (ioctl) {
> +	case VHOST_SCSI_SET_ENDPOINT:
> +		if (copy_from_user(&backend, argp, sizeof backend))
> +			return -EFAULT;
> +
> +		return vhost_scsi_set_endpoint(vs, &backend);
> +	case VHOST_SCSI_CLEAR_ENDPOINT:
> +		if (copy_from_user(&backend, argp, sizeof backend))
> +			return -EFAULT;
> +
> +		return vhost_scsi_clear_endpoint(vs, &backend);
> +	case VHOST_SCSI_GET_ABI_VERSION:
> +		if (copy_from_user(&backend, argp, sizeof backend))
> +			return -EFAULT;

Why are we reading this in BTW?

> +
> +		backend.abi_version = VHOST_SCSI_ABI_VERSION;
> +
> +		if (copy_to_user(argp, &backend, sizeof backend))
> +			return -EFAULT;
> +		return 0;
> +	case VHOST_GET_FEATURES:
> +		features = VHOST_FEATURES;
> +		if (copy_to_user(featurep, &features, sizeof features))
> +			return -EFAULT;
> +		return 0;
> +	case VHOST_SET_FEATURES:
> +		if (copy_from_user(&features, featurep, sizeof features))
> +			return -EFAULT;
> +		return vhost_scsi_set_features(vs, features);
> +	default:
> +		mutex_lock(&vs->dev.mutex);
> +		r = vhost_dev_ioctl(&vs->dev, ioctl, arg);
> +		mutex_unlock(&vs->dev.mutex);
> +		return r;
> +	}
> +}
> +
> +static const struct file_operations vhost_scsi_fops = {
> +	.owner          = THIS_MODULE,
> +	.release        = vhost_scsi_release,
> +	.unlocked_ioctl = vhost_scsi_ioctl,
> +	/* TODO compat ioctl? */

well?

> +	.open           = vhost_scsi_open,
> +	.llseek		= noop_llseek,
> +};
> +
> +static struct miscdevice vhost_scsi_misc = {
> +	MISC_DYNAMIC_MINOR,
> +	"vhost-scsi",
> +	&vhost_scsi_fops,
> +};
> +
> +static int __init vhost_scsi_register(void)
> +{
> +	return misc_register(&vhost_scsi_misc);
> +}
> +
> +static int vhost_scsi_deregister(void)
> +{
> +	return misc_deregister(&vhost_scsi_misc);
> +}
> +
> +static char *tcm_vhost_dump_proto_id(struct tcm_vhost_tport *tport)
> +{
> +	switch (tport->tport_proto_id) {
> +	case SCSI_PROTOCOL_SAS:
> +		return "SAS";
> +	case SCSI_PROTOCOL_FCP:
> +		return "FCP";
> +	case SCSI_PROTOCOL_ISCSI:
> +		return "iSCSI";
> +	default:
> +		break;
> +	}
> +
> +	return "Unknown";
> +}
> +
> +static int tcm_vhost_port_link(
> +	struct se_portal_group *se_tpg,
> +	struct se_lun *lun)

I'd like this and other places to be like this:
 static int tcm_vhost_port_link(struct se_portal_group *se_tpg,
 	struct se_lun *lun)

or
 static int
 tcm_vhost_port_link(struct se_portal_group *se_tpg,
		     struct se_lun *lun)

so that it's more like the rest of vhost code.


> +{
> +	struct tcm_vhost_tpg *tv_tpg = container_of(se_tpg,
> +				struct tcm_vhost_tpg, se_tpg);
> +
> +	atomic_inc(&tv_tpg->tv_tpg_port_count);
> +	smp_mb__after_atomic_inc();
> +
> +	return 0;
> +}
> +
> +static void tcm_vhost_port_unlink(
> +	struct se_portal_group *se_tpg,
> +	struct se_lun *se_lun)
> +{
> +	struct tcm_vhost_tpg *tv_tpg = container_of(se_tpg,
> +				struct tcm_vhost_tpg, se_tpg);
> +
> +	atomic_dec(&tv_tpg->tv_tpg_port_count);
> +	smp_mb__after_atomic_dec();
> +}
> +
> +static struct se_node_acl *tcm_vhost_make_nodeacl(
> +	struct se_portal_group *se_tpg,
> +	struct config_group *group,
> +	const char *name)
> +{
> +	struct se_node_acl *se_nacl, *se_nacl_new;
> +	struct tcm_vhost_nacl *nacl;
> +	u64 wwpn = 0;
> +	u32 nexus_depth;
> +
> +	/* tcm_vhost_parse_wwn(name, &wwpn, 1) < 0)
> +		return ERR_PTR(-EINVAL); */
> +	se_nacl_new = tcm_vhost_alloc_fabric_acl(se_tpg);
> +	if (!se_nacl_new)
> +		return ERR_PTR(-ENOMEM);
> +
> +	nexus_depth = 1;
> +	/*
> +	 * se_nacl_new may be released by core_tpg_add_initiator_node_acl()
> +	 * when converting a NodeACL from demo mode -> explict
> +	 */
> +	se_nacl = core_tpg_add_initiator_node_acl(se_tpg, se_nacl_new,
> +				name, nexus_depth);
> +	if (IS_ERR(se_nacl)) {
> +		tcm_vhost_release_fabric_acl(se_tpg, se_nacl_new);
> +		return se_nacl;
> +	}
> +	/*
> +	 * Locate our struct tcm_vhost_nacl and set the FC Nport WWPN
> +	 */
> +	nacl = container_of(se_nacl, struct tcm_vhost_nacl, se_node_acl);
> +	nacl->iport_wwpn = wwpn;
> +
> +	return se_nacl;
> +}
> +
> +static void tcm_vhost_drop_nodeacl(struct se_node_acl *se_acl)
> +{
> +	struct tcm_vhost_nacl *nacl = container_of(se_acl,
> +				struct tcm_vhost_nacl, se_node_acl);
> +	core_tpg_del_initiator_node_acl(se_acl->se_tpg, se_acl, 1);
> +	kfree(nacl);
> +}
> +
> +static int tcm_vhost_make_nexus(
> +	struct tcm_vhost_tpg *tv_tpg,
> +	const char *name)
> +{
> +	struct se_portal_group *se_tpg;
> +	struct tcm_vhost_nexus *tv_nexus;
> +
> +	mutex_lock(&tv_tpg->tv_tpg_mutex);
> +	if (tv_tpg->tpg_nexus) {
> +		mutex_unlock(&tv_tpg->tv_tpg_mutex);
> +		pr_debug("tv_tpg->tpg_nexus already exists\n");
> +		return -EEXIST;
> +	}
> +	se_tpg = &tv_tpg->se_tpg;
> +
> +	tv_nexus = kzalloc(sizeof(struct tcm_vhost_nexus), GFP_KERNEL);
> +	if (!tv_nexus) {
> +		mutex_unlock(&tv_tpg->tv_tpg_mutex);
> +		pr_err("Unable to allocate struct tcm_vhost_nexus\n");
> +		return -ENOMEM;
> +	}
> +	/*
> +	 *  Initialize the struct se_session pointer
> +	 */
> +	tv_nexus->tvn_se_sess = transport_init_session();
> +	if (IS_ERR(tv_nexus->tvn_se_sess)) {
> +		mutex_unlock(&tv_tpg->tv_tpg_mutex);
> +		kfree(tv_nexus);
> +		return -ENOMEM;
> +	}
> +	/*
> +	 * Since we are running in 'demo mode' this call with generate a
> +	 * struct se_node_acl for the tcm_vhost struct se_portal_group with
> +	 * the SCSI Initiator port name of the passed configfs group 'name'.
> +	 */
> +	tv_nexus->tvn_se_sess->se_node_acl = core_tpg_check_initiator_node_acl(
> +				se_tpg, (unsigned char *)name);
> +	if (!tv_nexus->tvn_se_sess->se_node_acl) {
> +		mutex_unlock(&tv_tpg->tv_tpg_mutex);
> +		pr_debug("core_tpg_check_initiator_node_acl() failed"
> +				" for %s\n", name);
> +		transport_free_session(tv_nexus->tvn_se_sess);
> +		kfree(tv_nexus);
> +		return -ENOMEM;
> +	}
> +	/*
> +	 * Now register the TCM vHost virtual I_T Nexus as active with the

I think s/vHost/vhost/ would be nice :)

> +	 * call to __transport_register_session()
> +	 */
> +	__transport_register_session(se_tpg, tv_nexus->tvn_se_sess->se_node_acl,
> +			tv_nexus->tvn_se_sess, tv_nexus);
> +	tv_tpg->tpg_nexus = tv_nexus;
> +
> +	mutex_unlock(&tv_tpg->tv_tpg_mutex);
> +	return 0;
> +}
> +
> +static int tcm_vhost_drop_nexus(
> +	struct tcm_vhost_tpg *tpg)
> +{
> +	struct se_session *se_sess;
> +	struct tcm_vhost_nexus *tv_nexus;
> +
> +	mutex_lock(&tpg->tv_tpg_mutex);
> +	tv_nexus = tpg->tpg_nexus;
> +	if (!tv_nexus) {
> +		mutex_unlock(&tpg->tv_tpg_mutex);
> +		return -ENODEV;
> +	}
> +
> +	se_sess = tv_nexus->tvn_se_sess;
> +	if (!se_sess) {
> +		mutex_unlock(&tpg->tv_tpg_mutex);
> +		return -ENODEV;
> +	}
> +
> +	if (atomic_read(&tpg->tv_tpg_port_count)) {
> +		mutex_unlock(&tpg->tv_tpg_mutex);
> +		pr_err("Unable to remove TCM_vHost I_T Nexus with"
> +			" active TPG port count: %d\n",
> +			atomic_read(&tpg->tv_tpg_port_count));
> +		return -EPERM;

EBUSY?


> +	}
> +
> +	if (atomic_read(&tpg->tv_tpg_vhost_count)) {
> +		mutex_unlock(&tpg->tv_tpg_mutex);
> +		pr_err("Unable to remove TCM_vHost I_T Nexus with"
> +			" active TPG vhost count: %d\n",
> +			atomic_read(&tpg->tv_tpg_vhost_count));
> +		return -EPERM;

Same?

> +	}
> +
> +	pr_debug("TCM_vHost_ConfigFS: Removing I_T Nexus to emulated"
> +		" %s Initiator Port: %s\n", tcm_vhost_dump_proto_id(tpg->tport),
> +		tv_nexus->tvn_se_sess->se_node_acl->initiatorname);
> +	/*
> +	 * Release the SCSI I_T Nexus to the emulated vHost Target Port
> +	 */
> +	transport_deregister_session(tv_nexus->tvn_se_sess);
> +	tpg->tpg_nexus = NULL;
> +	mutex_unlock(&tpg->tv_tpg_mutex);
> +
> +	kfree(tv_nexus);
> +	return 0;
> +}
> +
> +static ssize_t tcm_vhost_tpg_show_nexus(
> +	struct se_portal_group *se_tpg,
> +	char *page)
> +{
> +	struct tcm_vhost_tpg *tv_tpg = container_of(se_tpg,
> +				struct tcm_vhost_tpg, se_tpg);
> +	struct tcm_vhost_nexus *tv_nexus;
> +	ssize_t ret;
> +
> +	mutex_lock(&tv_tpg->tv_tpg_mutex);
> +	tv_nexus = tv_tpg->tpg_nexus;
> +	if (!tv_nexus) {
> +		mutex_unlock(&tv_tpg->tv_tpg_mutex);
> +		return -ENODEV;
> +	}
> +	ret = snprintf(page, PAGE_SIZE, "%s\n",
> +			tv_nexus->tvn_se_sess->se_node_acl->initiatorname);
> +	mutex_unlock(&tv_tpg->tv_tpg_mutex);
> +
> +	return ret;
> +}
> +
> +static ssize_t tcm_vhost_tpg_store_nexus(
> +	struct se_portal_group *se_tpg,
> +	const char *page,
> +	size_t count)
> +{
> +	struct tcm_vhost_tpg *tv_tpg = container_of(se_tpg,
> +				struct tcm_vhost_tpg, se_tpg);
> +	struct tcm_vhost_tport *tport_wwn = tv_tpg->tport;
> +	unsigned char i_port[TCM_VHOST_NAMELEN], *ptr, *port_ptr;
> +	int ret;
> +	/*
> +	 * Shutdown the active I_T nexus if 'NULL' is passed..
> +	 */
> +	if (!strncmp(page, "NULL", 4)) {
> +		ret = tcm_vhost_drop_nexus(tv_tpg);
> +		return (!ret) ? count : ret;
> +	}
> +	/*
> +	 * Otherwise make sure the passed virtual Initiator port WWN matches
> +	 * the fabric protocol_id set in tcm_vhost_make_tport(), and call
> +	 * tcm_vhost_make_nexus().
> +	 */
> +	if (strlen(page) >= TCM_VHOST_NAMELEN) {
> +		pr_err("Emulated NAA Sas Address: %s, exceeds"
> +				" max: %d\n", page, TCM_VHOST_NAMELEN);
> +		return -EINVAL;
> +	}
> +	snprintf(&i_port[0], TCM_VHOST_NAMELEN, "%s", page);
> +
> +	ptr = strstr(i_port, "naa.");
> +	if (ptr) {
> +		if (tport_wwn->tport_proto_id != SCSI_PROTOCOL_SAS) {
> +			pr_err("Passed SAS Initiator Port %s does not"
> +				" match target port protoid: %s\n", i_port,
> +				tcm_vhost_dump_proto_id(tport_wwn));
> +			return -EINVAL;
> +		}
> +		port_ptr = &i_port[0];
> +		goto check_newline;
> +	}
> +	ptr = strstr(i_port, "fc.");
> +	if (ptr) {
> +		if (tport_wwn->tport_proto_id != SCSI_PROTOCOL_FCP) {
> +			pr_err("Passed FCP Initiator Port %s does not"
> +				" match target port protoid: %s\n", i_port,
> +				tcm_vhost_dump_proto_id(tport_wwn));
> +			return -EINVAL;
> +		}
> +		port_ptr = &i_port[3]; /* Skip over "fc." */
> +		goto check_newline;
> +	}
> +	ptr = strstr(i_port, "iqn.");
> +	if (ptr) {
> +		if (tport_wwn->tport_proto_id != SCSI_PROTOCOL_ISCSI) {
> +			pr_err("Passed iSCSI Initiator Port %s does not"
> +				" match target port protoid: %s\n", i_port,
> +				tcm_vhost_dump_proto_id(tport_wwn));
> +			return -EINVAL;
> +		}
> +		port_ptr = &i_port[0];
> +		goto check_newline;
> +	}
> +	pr_err("Unable to locate prefix for emulated Initiator Port:"
> +			" %s\n", i_port);
> +	return -EINVAL;
> +	/*
> +	 * Clear any trailing newline for the NAA WWN
> +	 */
> +check_newline:
> +	if (i_port[strlen(i_port)-1] == '\n')
> +		i_port[strlen(i_port)-1] = '\0';
> +
> +	ret = tcm_vhost_make_nexus(tv_tpg, port_ptr);
> +	if (ret < 0)
> +		return ret;
> +
> +	return count;
> +}
> +
> +TF_TPG_BASE_ATTR(tcm_vhost, nexus, S_IRUGO | S_IWUSR);
> +
> +static struct configfs_attribute *tcm_vhost_tpg_attrs[] = {
> +	&tcm_vhost_tpg_nexus.attr,
> +	NULL,
> +};
> +
> +static struct se_portal_group *tcm_vhost_make_tpg(
> +	struct se_wwn *wwn,
> +	struct config_group *group,
> +	const char *name)
> +{
> +	struct tcm_vhost_tport *tport = container_of(wwn,
> +			struct tcm_vhost_tport, tport_wwn);
> +
> +	struct tcm_vhost_tpg *tpg;
> +	unsigned long tpgt;
> +	int ret;
> +
> +	if (strstr(name, "tpgt_") != name)
> +		return ERR_PTR(-EINVAL);
> +	if (kstrtoul(name + 5, 10, &tpgt) || tpgt > UINT_MAX)
> +		return ERR_PTR(-EINVAL);
> +
> +	tpg = kzalloc(sizeof(struct tcm_vhost_tpg), GFP_KERNEL);
> +	if (!tpg) {
> +		pr_err("Unable to allocate struct tcm_vhost_tpg");
> +		return ERR_PTR(-ENOMEM);
> +	}
> +	mutex_init(&tpg->tv_tpg_mutex);
> +	INIT_LIST_HEAD(&tpg->tv_tpg_list);
> +	tpg->tport = tport;
> +	tpg->tport_tpgt = tpgt;
> +
> +	ret = core_tpg_register(&tcm_vhost_fabric_configfs->tf_ops, wwn,
> +				&tpg->se_tpg, tpg, TRANSPORT_TPG_TYPE_NORMAL);
> +	if (ret < 0) {
> +		kfree(tpg);
> +		return NULL;
> +	}
> +	mutex_lock(&tcm_vhost_mutex);
> +	list_add_tail(&tpg->tv_tpg_list, &tcm_vhost_list);
> +	mutex_unlock(&tcm_vhost_mutex);
> +
> +	return &tpg->se_tpg;
> +}
> +
> +static void tcm_vhost_drop_tpg(struct se_portal_group *se_tpg)
> +{
> +	struct tcm_vhost_tpg *tpg = container_of(se_tpg,
> +				struct tcm_vhost_tpg, se_tpg);
> +
> +	mutex_lock(&tcm_vhost_mutex);
> +	list_del(&tpg->tv_tpg_list);
> +	mutex_unlock(&tcm_vhost_mutex);
> +	/*
> +	 * Release the virtual I_T Nexus for this vHost TPG
> +	 */
> +	tcm_vhost_drop_nexus(tpg);
> +	/*
> +	 * Deregister the se_tpg from TCM..
> +	 */
> +	core_tpg_deregister(se_tpg);
> +	kfree(tpg);
> +}
> +
> +static struct se_wwn *tcm_vhost_make_tport(
> +	struct target_fabric_configfs *tf,
> +	struct config_group *group,
> +	const char *name)
> +{
> +	struct tcm_vhost_tport *tport;
> +	char *ptr;
> +	u64 wwpn = 0;
> +	int off = 0;
> +
> +	/* if (tcm_vhost_parse_wwn(name, &wwpn, 1) < 0)
> +		return ERR_PTR(-EINVAL); */
> +
> +	tport = kzalloc(sizeof(struct tcm_vhost_tport), GFP_KERNEL);
> +	if (!tport) {
> +		pr_err("Unable to allocate struct tcm_vhost_tport");
> +		return ERR_PTR(-ENOMEM);
> +	}
> +	tport->tport_wwpn = wwpn;
> +	/*
> +	 * Determine the emulated Protocol Identifier and Target Port Name
> +	 * based on the incoming configfs directory name.
> +	 */
> +	ptr = strstr(name, "naa.");
> +	if (ptr) {
> +		tport->tport_proto_id = SCSI_PROTOCOL_SAS;
> +		goto check_len;
> +	}
> +	ptr = strstr(name, "fc.");
> +	if (ptr) {
> +		tport->tport_proto_id = SCSI_PROTOCOL_FCP;
> +		off = 3; /* Skip over "fc." */
> +		goto check_len;
> +	}
> +	ptr = strstr(name, "iqn.");
> +	if (ptr) {
> +		tport->tport_proto_id = SCSI_PROTOCOL_ISCSI;
> +		goto check_len;
> +	}
> +
> +	pr_err("Unable to locate prefix for emulated Target Port:"
> +			" %s\n", name);
> +	kfree(tport);
> +	return ERR_PTR(-EINVAL);
> +
> +check_len:
> +	if (strlen(name) >= TCM_VHOST_NAMELEN) {
> +		pr_err("Emulated %s Address: %s, exceeds"
> +			" max: %d\n", name, tcm_vhost_dump_proto_id(tport),
> +			TCM_VHOST_NAMELEN);
> +		kfree(tport);
> +		return ERR_PTR(-EINVAL);
> +	}
> +	snprintf(&tport->tport_name[0], TCM_VHOST_NAMELEN, "%s", &name[off]);
> +
> +	pr_debug("TCM_VHost_ConfigFS: Allocated emulated Target"
> +		" %s Address: %s\n", tcm_vhost_dump_proto_id(tport), name);
> +
> +	return &tport->tport_wwn;
> +}
> +
> +static void tcm_vhost_drop_tport(struct se_wwn *wwn)
> +{
> +	struct tcm_vhost_tport *tport = container_of(wwn,
> +				struct tcm_vhost_tport, tport_wwn);
> +
> +	pr_debug("TCM_VHost_ConfigFS: Deallocating emulated Target"
> +		" %s Address: %s\n", tcm_vhost_dump_proto_id(tport),
> +		tport->tport_name);
> +
> +	kfree(tport);
> +}
> +
> +static ssize_t tcm_vhost_wwn_show_attr_version(
> +	struct target_fabric_configfs *tf,
> +	char *page)
> +{
> +	return sprintf(page, "TCM_VHOST fabric module %s on %s/%s"
> +		"on "UTS_RELEASE"\n", TCM_VHOST_VERSION, utsname()->sysname,
> +		utsname()->machine);
> +}
> +
> +TF_WWN_ATTR_RO(tcm_vhost, version);
> +
> +static struct configfs_attribute *tcm_vhost_wwn_attrs[] = {
> +	&tcm_vhost_wwn_version.attr,
> +	NULL,
> +};
> +
> +static struct target_core_fabric_ops tcm_vhost_ops = {
> +	.get_fabric_name		= tcm_vhost_get_fabric_name,
> +	.get_fabric_proto_ident		= tcm_vhost_get_fabric_proto_ident,
> +	.tpg_get_wwn			= tcm_vhost_get_fabric_wwn,
> +	.tpg_get_tag			= tcm_vhost_get_tag,
> +	.tpg_get_default_depth		= tcm_vhost_get_default_depth,
> +	.tpg_get_pr_transport_id	= tcm_vhost_get_pr_transport_id,
> +	.tpg_get_pr_transport_id_len	= tcm_vhost_get_pr_transport_id_len,
> +	.tpg_parse_pr_out_transport_id	= tcm_vhost_parse_pr_out_transport_id,
> +	.tpg_check_demo_mode		= tcm_vhost_check_true,
> +	.tpg_check_demo_mode_cache	= tcm_vhost_check_true,
> +	.tpg_check_demo_mode_write_protect = tcm_vhost_check_false,
> +	.tpg_check_prod_mode_write_protect = tcm_vhost_check_false,
> +	.tpg_alloc_fabric_acl		= tcm_vhost_alloc_fabric_acl,
> +	.tpg_release_fabric_acl		= tcm_vhost_release_fabric_acl,
> +	.tpg_get_inst_index		= tcm_vhost_tpg_get_inst_index,
> +	.release_cmd			= tcm_vhost_release_cmd,
> +	.shutdown_session		= tcm_vhost_shutdown_session,
> +	.close_session			= tcm_vhost_close_session,
> +	.sess_get_index			= tcm_vhost_sess_get_index,
> +	.sess_get_initiator_sid		= NULL,
> +	.write_pending			= tcm_vhost_write_pending,
> +	.write_pending_status		= tcm_vhost_write_pending_status,
> +	.set_default_node_attributes	= tcm_vhost_set_default_node_attrs,
> +	.get_task_tag			= tcm_vhost_get_task_tag,
> +	.get_cmd_state			= tcm_vhost_get_cmd_state,
> +	.queue_data_in			= tcm_vhost_queue_data_in,
> +	.queue_status			= tcm_vhost_queue_status,
> +	.queue_tm_rsp			= tcm_vhost_queue_tm_rsp,
> +	.get_fabric_sense_len		= tcm_vhost_get_fabric_sense_len,
> +	.set_fabric_sense_len		= tcm_vhost_set_fabric_sense_len,
> +	/*
> +	 * Setup callers for generic logic in target_core_fabric_configfs.c
> +	 */
> +	.fabric_make_wwn		= tcm_vhost_make_tport,
> +	.fabric_drop_wwn		= tcm_vhost_drop_tport,
> +	.fabric_make_tpg		= tcm_vhost_make_tpg,
> +	.fabric_drop_tpg		= tcm_vhost_drop_tpg,
> +	.fabric_post_link		= tcm_vhost_port_link,
> +	.fabric_pre_unlink		= tcm_vhost_port_unlink,
> +	.fabric_make_np			= NULL,
> +	.fabric_drop_np			= NULL,
> +	.fabric_make_nodeacl		= tcm_vhost_make_nodeacl,
> +	.fabric_drop_nodeacl		= tcm_vhost_drop_nodeacl,
> +};
> +
> +static int tcm_vhost_register_configfs(void)
> +{
> +	struct target_fabric_configfs *fabric;
> +	int ret;
> +
> +	pr_debug("TCM_VHOST fabric module %s on %s/%s"
> +		" on "UTS_RELEASE"\n", TCM_VHOST_VERSION, utsname()->sysname,
> +		utsname()->machine);
> +	/*
> +	 * Register the top level struct config_item_type with TCM core
> +	 */
> +	fabric = target_fabric_configfs_init(THIS_MODULE, "vhost");
> +	if (IS_ERR(fabric)) {
> +		pr_err("target_fabric_configfs_init() failed\n");
> +		return PTR_ERR(fabric);
> +	}
> +	/*
> +	 * Setup fabric->tf_ops from our local tcm_vhost_ops
> +	 */
> +	fabric->tf_ops = tcm_vhost_ops;
> +	/*
> +	 * Setup default attribute lists for various fabric->tf_cit_tmpl
> +	 */
> +	TF_CIT_TMPL(fabric)->tfc_wwn_cit.ct_attrs = tcm_vhost_wwn_attrs;
> +	TF_CIT_TMPL(fabric)->tfc_tpg_base_cit.ct_attrs = tcm_vhost_tpg_attrs;
> +	TF_CIT_TMPL(fabric)->tfc_tpg_attrib_cit.ct_attrs = NULL;
> +	TF_CIT_TMPL(fabric)->tfc_tpg_param_cit.ct_attrs = NULL;
> +	TF_CIT_TMPL(fabric)->tfc_tpg_np_base_cit.ct_attrs = NULL;
> +	TF_CIT_TMPL(fabric)->tfc_tpg_nacl_base_cit.ct_attrs = NULL;
> +	TF_CIT_TMPL(fabric)->tfc_tpg_nacl_attrib_cit.ct_attrs = NULL;
> +	TF_CIT_TMPL(fabric)->tfc_tpg_nacl_auth_cit.ct_attrs = NULL;
> +	TF_CIT_TMPL(fabric)->tfc_tpg_nacl_param_cit.ct_attrs = NULL;
> +	/*
> +	 * Register the fabric for use within TCM
> +	 */
> +	ret = target_fabric_configfs_register(fabric);
> +	if (ret < 0) {
> +		pr_err("target_fabric_configfs_register() failed"
> +				" for TCM_VHOST\n");
> +		return ret;
> +	}
> +	/*
> +	 * Setup our local pointer to *fabric
> +	 */
> +	tcm_vhost_fabric_configfs = fabric;
> +	pr_debug("TCM_VHOST[0] - Set fabric -> tcm_vhost_fabric_configfs\n");
> +	return 0;
> +};
> +
> +static void tcm_vhost_deregister_configfs(void)
> +{
> +	if (!tcm_vhost_fabric_configfs)
> +		return;
> +
> +	target_fabric_configfs_deregister(tcm_vhost_fabric_configfs);
> +	tcm_vhost_fabric_configfs = NULL;
> +	pr_debug("TCM_VHOST[0] - Cleared tcm_vhost_fabric_configfs\n");
> +};
> +
> +static int __init tcm_vhost_init(void)
> +{
> +	int ret = -ENOMEM;
> +
> +	tcm_vhost_workqueue = alloc_workqueue("tcm_vhost", 0, 0);
> +	if (!tcm_vhost_workqueue)
> +		goto out;

Pls add a comment explaining why we need our own workqueue
and aren't using the system one instead.

> +
> +	ret = vhost_scsi_register();
> +	if (ret < 0)
> +		goto out_destroy_workqueue;
> +
> +	ret = tcm_vhost_register_configfs();
> +	if (ret < 0)
> +		goto out_vhost_scsi_deregister;
> +
> +	return 0;
> +
> +out_vhost_scsi_deregister:
> +	vhost_scsi_deregister();
> +out_destroy_workqueue:
> +	destroy_workqueue(tcm_vhost_workqueue);
> +out:
> +	return ret;
> +};
> +
> +static void tcm_vhost_exit(void)
> +{
> +	tcm_vhost_deregister_configfs();
> +	vhost_scsi_deregister();
> +	destroy_workqueue(tcm_vhost_workqueue);
> +};
> +
> +MODULE_DESCRIPTION("TCM_VHOST series fabric driver");
> +MODULE_LICENSE("GPL");
> +module_init(tcm_vhost_init);
> +module_exit(tcm_vhost_exit);
> diff --git a/drivers/vhost/tcm_vhost.h b/drivers/vhost/tcm_vhost.h
> new file mode 100644
> index 0000000..c983ed2
> --- /dev/null
> +++ b/drivers/vhost/tcm_vhost.h
> @@ -0,0 +1,101 @@
> +#define TCM_VHOST_VERSION  "v0.1"
> +#define TCM_VHOST_NAMELEN 256
> +#define TCM_VHOST_MAX_CDB_SIZE 32
> +
> +struct tcm_vhost_cmd {
> +	/* Descriptor from vhost_get_vq_desc() for virt_queue segment */
> +	int tvc_vq_desc;
> +	/* The Tag from include/linux/virtio_scsi.h:struct virtio_scsi_cmd_req */
> +	u64 tvc_tag;
> +	/* The number of scatterlists associated with this cmd */
> +	u32 tvc_sgl_count;
> +	/* Saved unpacked SCSI LUN for tcm_vhost_submission_work() */
> +	u32 tvc_lun;
> +	/* Pointer to the SGL formatted memory from virtio-scsi */
> +	struct scatterlist *tvc_sgl;
> +	/* Pointer to response */
> +	struct virtio_scsi_cmd_resp __user *tvc_resp;
> +	/* Pointer to vhost_scsi for our device */
> +	struct vhost_scsi *tvc_vhost;
> +	/* The TCM I/O descriptor that is accessed via container_of() */
> +	struct se_cmd tvc_se_cmd;
> +	/* work item used for cmwq dispatch to tcm_vhost_submission_work() */
> +	struct work_struct work;
> +	/* Copy of the incoming SCSI command descriptor block (CDB) */
> +	unsigned char tvc_cdb[TCM_VHOST_MAX_CDB_SIZE];
> +	/* Sense buffer that will be mapped into outgoing status */
> +	unsigned char tvc_sense_buf[TRANSPORT_SENSE_BUFFER];
> +	/* Completed commands list, serviced from vhost worker thread */
> +	struct list_head tvc_completion_list;
> +};
> +
> +struct tcm_vhost_nexus {
> +	/* Pointer to TCM session for I_T Nexus */
> +	struct se_session *tvn_se_sess;
> +};
> +
> +struct tcm_vhost_nacl {
> +	/* Binary World Wide unique Port Name for Vhost Initiator port */
> +	u64 iport_wwpn;
> +	/* ASCII formatted WWPN for Sas Initiator port */
> +	char iport_name[TCM_VHOST_NAMELEN];
> +	/* Returned by tcm_vhost_make_nodeacl() */
> +	struct se_node_acl se_node_acl;
> +};
> +
> +struct tcm_vhost_tpg {
> +	/* Vhost port target portal group tag for TCM */
> +	u16 tport_tpgt;
> +	/* Used to track number of TPG Port/Lun Links wrt to explict I_T Nexus shutdown */
> +	atomic_t tv_tpg_port_count;
> +	/* Used for vhost_scsi device reference to tpg_nexus */
> +	atomic_t tv_tpg_vhost_count;
> +	/* list for tcm_vhost_list */
> +	struct list_head tv_tpg_list;
> +	/* Used to protect access for tpg_nexus */
> +	struct mutex tv_tpg_mutex;

would it be easier to just use dev mutex instead?

> +	/* Pointer to the TCM VHost I_T Nexus for this TPG endpoint */
> +	struct tcm_vhost_nexus *tpg_nexus;
> +	/* Pointer back to tcm_vhost_tport */
> +	struct tcm_vhost_tport *tport;
> +	/* Returned by tcm_vhost_make_tpg() */
> +	struct se_portal_group se_tpg;
> +};
> +
> +struct tcm_vhost_tport {
> +	/* SCSI protocol the tport is providing */
> +	u8 tport_proto_id;
> +	/* Binary World Wide unique Port Name for Vhost Target port */
> +	u64 tport_wwpn;
> +	/* ASCII formatted WWPN for Vhost Target port */
> +	char tport_name[TCM_VHOST_NAMELEN];
> +	/* Returned by tcm_vhost_make_tport() */
> +	struct se_wwn tport_wwn;
> +};
> +
> +/*
> + * As per request from MST, keep TCM_VHOST related ioctl defines out of
> + * linux/vhost.h (user-space) for now..
> + */
> +
> +#include <linux/vhost.h>
> +
> +/*
> + * Used by QEMU userspace to ensure a consistent vhost-scsi ABI.
> + *
> + * ABI Rev 0: July 2012 version starting point for v3.6-rc merge candidate +
> + *            RFC-v2 vhost-scsi userspace.  Add GET_ABI_VERSION ioctl usage
> + */
> +
> +#define VHOST_SCSI_ABI_VERSION	0
> +
> +struct vhost_scsi_target {
> +	int abi_version;
> +	unsigned char vhost_wwpn[TRANSPORT_IQN_LEN];
> +	unsigned short vhost_tpgt;
> +};
> +
> +/* VHOST_SCSI specific defines */
> +#define VHOST_SCSI_SET_ENDPOINT _IOW(VHOST_VIRTIO, 0x40, struct vhost_scsi_target)
> +#define VHOST_SCSI_CLEAR_ENDPOINT _IOW(VHOST_VIRTIO, 0x41, struct vhost_scsi_target)
> +#define VHOST_SCSI_GET_ABI_VERSION _IOW(VHOST_VIRTIO, 0x42, struct vhost_scsi_target)

CLEAR_ENDPOINT and SET_ENDPOINT commands get an abi version
too but it's ignored there. Intentional?
Why not
#define VHOST_SCSI_GET_ABI_VERSION _IOW(VHOST_VIRTIO, 0x42, int)
and then you avoid changing vhost_scsi_target ...

Also, let's add a comment like

/* Changing this breaks userspace. */

so we remember never to change this value.

> -- 
> 1.7.2.5

On Sun, 2012-07-29 at 16:40 +0300, Michael S. Tsirkin wrote: 
> On Thu, Jul 26, 2012 at 11:43:20PM +0000, Nicholas A. Bellinger wrote:
> > From: Nicholas Bellinger <nab@linux-iscsi.org>
> > 
> > Hello KVM + QEMU folks,
> > 
> > This is -v5 of the in-flight tcm_vhost fabric driver for KVM host virtualized
> > target support using the in-kernel storage stack with for-3.6 code.
> > 
> > The changes since -v4 have been pretty minimal.  A new GET_ABI_VERSION ioctl
> > has been added as requested by Anthony & Co, and after some back <-> forth on
> > the lists we've decided upon a starting point of VHOST_SCSI_ABI_VERSION=0,
> > and vhost-scsi RFC userspace has been updated accordingly.
> > 
> > Along with that, a few handfuls of vq related error messages where converted
> > to use vq_err as requested by MST, along with some minor checkpatch fixes.
> > 
> > So this point everything required to run tcm_vhost from drivers/target +
> > drivers/vhost, and virtio-scsi LLD bugfix has been merged into v3.6-rc0 code.
> > 
> > Please have a look and let us know if there are any last-minute pre-merge
> > comments ahead of MST returning from holiday this weekend.
> > 
> > Thank you!
> > 
> > --nab
> 
> Acked-by: Michael S. Tsirkin <mst@redhat.com>
> 
> some comments below but can be fixed in-tree I think.
> 

Thanks alot MST!

I've added your ACK for -v5 RFC code that's in 07302012 linux-next, and
made the changes requested below as an incremental patch that will be
sending out shortly.

My comments are inline below..

> > Changelog v4 -> v5:
> > 
> >   Expose ABI version via VHOST_SCSI_GET_ABI_VERSION + use Rev 0 as
> >   starting point for v3.6-rc code (Stefan + ALiguori + nab)
> >   Convert vhost_scsi_handle_vq() to vq_err() (nab + MST)
> >   Minor style fixes from checkpatch (nab)
> > 
> > Changelog v3 -> v4:
> > 
> >   Rename vhost_vring_target -> vhost_scsi_target (mst + nab)
> >   Use TRANSPORT_IQN_LEN in vhost_scsi_target->vhost_wwpn[] def (nab)
> >   Move back to drivers/vhost/, and just use drivers/vhost/Kconfig.tcm (mst)
> >   Move TCM_VHOST related ioctl defines from include/linux/vhost.h ->
> >   drivers/vhost/tcm_vhost.h as requested by MST (nab)
> >   Move Kbuild.tcm include from drivers/staging -> drivers/vhost/, and
> >   just use 'if STAGING' around 'source drivers/vhost/Kbuild.tcm'
> > 
> > Changelog v2 -> v3:
> > 
> >   Unlock on error in tcm_vhost_drop_nexus() (DanC)
> >   Fix strlen() doesn't count the terminator (DanC)
> >   Call kfree() on an error path (DanC)
> >   Convert tcm_vhost_write_pending to use target_execute_cmd (hch + nab)
> >   Fix another strlen() off by one in tcm_vhost_make_tport (DanC)
> >   Add option under drivers/staging/Kconfig, and move to drivers/vhost/tcm/
> >   as requested by MST (nab)
> > 
> > Changelog v1 -> v2:
> > 
> >   Fix tv_cmd completion -> release SGL memory leak (nab)
> >   Fix sparse warnings for static variable usage ((Fengguang Wu)
> >   Fix sparse warnings for min() typing + printk format specs (Fengguang Wu)
> >   Convert to cmwq submission for I/O dispatch (nab + hch)
> > 
> > Changelog v0 -> v1:
> > 
> >   Merge into single source + header file, and move to drivers/vhost/
> > 
> > Cc: Michael S. Tsirkin <mst@redhat.com>
> > Cc: Stefan Hajnoczi <stefanha@linux.vnet.ibm.com>
> > Cc: Anthony Liguori <aliguori@us.ibm.com>
> > Cc: Zhi Yong Wu <wuzhy@cn.ibm.com>
> > Cc: Paolo Bonzini <pbonzini@redhat.com>
> > Cc: Christoph Hellwig <hch@lst.de>
> > Cc: Hannes Reinecke <hare@suse.de>
> > Cc: Jens Axboe <axboe@kernel.dk>
> > Signed-off-by: Nicholas Bellinger <nab@linux-iscsi.org>
> > ---
> >  drivers/vhost/Kconfig     |    3 +
> >  drivers/vhost/Kconfig.tcm |    6 +
> >  drivers/vhost/Makefile    |    2 +
> >  drivers/vhost/tcm_vhost.c | 1628 +++++++++++++++++++++++++++++++++++++++++++++
> >  drivers/vhost/tcm_vhost.h |  101 +++
> >  5 files changed, 1740 insertions(+), 0 deletions(-)
> >  create mode 100644 drivers/vhost/Kconfig.tcm
> >  create mode 100644 drivers/vhost/tcm_vhost.c
> >  create mode 100644 drivers/vhost/tcm_vhost.h
> > 
> > diff --git a/drivers/vhost/Kconfig b/drivers/vhost/Kconfig
> > index e4e2fd1..202bba6 100644
> > --- a/drivers/vhost/Kconfig
> > +++ b/drivers/vhost/Kconfig
> > @@ -9,3 +9,6 @@ config VHOST_NET
> >  	  To compile this driver as a module, choose M here: the module will
> >  	  be called vhost_net.
> >  
> > +if STAGING
> > +source "drivers/vhost/Kconfig.tcm"
> > +endif
> > diff --git a/drivers/vhost/Kconfig.tcm b/drivers/vhost/Kconfig.tcm
> > new file mode 100644
> > index 0000000..a9c6f76
> > --- /dev/null
> > +++ b/drivers/vhost/Kconfig.tcm
> > @@ -0,0 +1,6 @@
> > +config TCM_VHOST
> > +	tristate "TCM_VHOST fabric module (EXPERIMENTAL)"
> > +	depends on TARGET_CORE && EVENTFD && EXPERIMENTAL && m
> > +	default n
> > +	---help---
> > +	Say M here to enable the TCM_VHOST fabric module for use with virtio-scsi guests
> > diff --git a/drivers/vhost/Makefile b/drivers/vhost/Makefile
> > index 72dd020..a27b053 100644
> > --- a/drivers/vhost/Makefile
> > +++ b/drivers/vhost/Makefile
> > @@ -1,2 +1,4 @@
> >  obj-$(CONFIG_VHOST_NET) += vhost_net.o
> >  vhost_net-y := vhost.o net.o
> > +
> > +obj-$(CONFIG_TCM_VHOST) += tcm_vhost.o
> > diff --git a/drivers/vhost/tcm_vhost.c b/drivers/vhost/tcm_vhost.c
> > new file mode 100644
> > index 0000000..fb36654
> > --- /dev/null
> > +++ b/drivers/vhost/tcm_vhost.c
> > @@ -0,0 +1,1628 @@
> > +/*******************************************************************************
> > + * Vhost kernel TCM fabric driver for virtio SCSI initiators
> > + *
> > + * (C) Copyright 2010-2012 RisingTide Systems LLC.
> > + * (C) Copyright 2010-2012 IBM Corp.
> > + *
> > + * Licensed to the Linux Foundation under the General Public License (GPL) version 2.
> > + *
> > + * Authors: Nicholas A. Bellinger <nab@risingtidesystems.com>
> > + *          Stefan Hajnoczi <stefanha@linux.vnet.ibm.com>
> > + *
> > + * This program is free software; you can redistribute it and/or modify
> > + * it under the terms of the GNU General Public License as published by
> > + * the Free Software Foundation; either version 2 of the License, or
> > + * (at your option) any later version.
> > + *
> > + * This program is distributed in the hope that it will be useful,
> > + * but WITHOUT ANY WARRANTY; without even the implied warranty of
> > + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
> > + * GNU General Public License for more details.
> > + *
> > + ****************************************************************************/
> > +
> > +#include <linux/module.h>
> > +#include <linux/moduleparam.h>
> > +#include <generated/utsrelease.h>
> > +#include <linux/utsname.h>
> > +#include <linux/init.h>
> > +#include <linux/slab.h>
> > +#include <linux/kthread.h>
> > +#include <linux/types.h>
> > +#include <linux/string.h>
> > +#include <linux/configfs.h>
> > +#include <linux/ctype.h>
> > +#include <linux/compat.h>
> > +#include <linux/eventfd.h>
> > +#include <linux/vhost.h>
> > +#include <linux/fs.h>
> > +#include <linux/miscdevice.h>
> > +#include <asm/unaligned.h>
> > +#include <scsi/scsi.h>
> > +#include <scsi/scsi_tcq.h>
> > +#include <target/target_core_base.h>
> > +#include <target/target_core_fabric.h>
> > +#include <target/target_core_fabric_configfs.h>
> > +#include <target/target_core_configfs.h>
> > +#include <target/configfs_macros.h>
> > +#include <linux/vhost.h>
> > +#include <linux/virtio_net.h> /* TODO vhost.h currently depends on this */
> > +#include <linux/virtio_scsi.h>
> > +
> > +#include "vhost.c"
> > +#include "vhost.h"
> > +#include "tcm_vhost.h"
> > +
> > +struct vhost_scsi {
> > +	atomic_t vhost_ref_cnt;
> > +	struct tcm_vhost_tpg *vs_tpg;
> 
> Would b enice to add a note on locking about this field.
> 

Done

> > +	struct vhost_dev dev;
> > +	struct vhost_virtqueue vqs[3];
> > +
> > +	struct vhost_work vs_completion_work; /* cmd completion work item */
> > +	struct list_head vs_completion_list;  /* cmd completion queue */
> > +	spinlock_t vs_completion_lock;        /* protects s_completion_list */
> > +};
> > +
> > +/* Local pointer to allocated TCM configfs fabric module */
> > +static struct target_fabric_configfs *tcm_vhost_fabric_configfs;
> > +
> > +static struct workqueue_struct *tcm_vhost_workqueue;
> > +
> > +/* Global spinlock to protect tcm_vhost TPG list for vhost IOCTL access */
> > +static DEFINE_MUTEX(tcm_vhost_mutex);
> > +static LIST_HEAD(tcm_vhost_list);
> > +
> > +static int tcm_vhost_check_true(struct se_portal_group *se_tpg)
> > +{
> > +	return 1;
> > +}
> > +
> > +static int tcm_vhost_check_false(struct se_portal_group *se_tpg)
> > +{
> > +	return 0;
> > +}
> > +
> > +static char *tcm_vhost_get_fabric_name(void)
> > +{
> > +	return "vhost";
> > +}
> > +
> > +static u8 tcm_vhost_get_fabric_proto_ident(struct se_portal_group *se_tpg)
> > +{
> > +	struct tcm_vhost_tpg *tpg = container_of(se_tpg,
> > +				struct tcm_vhost_tpg, se_tpg);
> > +	struct tcm_vhost_tport *tport = tpg->tport;
> > +
> > +	switch (tport->tport_proto_id) {
> > +	case SCSI_PROTOCOL_SAS:
> > +		return sas_get_fabric_proto_ident(se_tpg);
> > +	case SCSI_PROTOCOL_FCP:
> > +		return fc_get_fabric_proto_ident(se_tpg);
> > +	case SCSI_PROTOCOL_ISCSI:
> > +		return iscsi_get_fabric_proto_ident(se_tpg);
> > +	default:
> > +		pr_err("Unknown tport_proto_id: 0x%02x, using"
> > +			" SAS emulation\n", tport->tport_proto_id);
> > +		break;
> > +	}
> > +
> > +	return sas_get_fabric_proto_ident(se_tpg);
> > +}
> > +
> > +static char *tcm_vhost_get_fabric_wwn(struct se_portal_group *se_tpg)
> > +{
> > +	struct tcm_vhost_tpg *tpg = container_of(se_tpg,
> > +				struct tcm_vhost_tpg, se_tpg);
> > +	struct tcm_vhost_tport *tport = tpg->tport;
> > +
> > +	return &tport->tport_name[0];
> > +}
> > +
> > +static u16 tcm_vhost_get_tag(struct se_portal_group *se_tpg)
> > +{
> > +	struct tcm_vhost_tpg *tpg = container_of(se_tpg,
> > +				struct tcm_vhost_tpg, se_tpg);
> > +	return tpg->tport_tpgt;
> > +}
> > +
> > +static u32 tcm_vhost_get_default_depth(struct se_portal_group *se_tpg)
> > +{
> > +	return 1;
> > +}
> > +
> > +static u32 tcm_vhost_get_pr_transport_id(
> > +	struct se_portal_group *se_tpg,
> > +	struct se_node_acl *se_nacl,
> > +	struct t10_pr_registration *pr_reg,
> > +	int *format_code,
> > +	unsigned char *buf)
> > +{
> > +	struct tcm_vhost_tpg *tpg = container_of(se_tpg,
> > +				struct tcm_vhost_tpg, se_tpg);
> > +	struct tcm_vhost_tport *tport = tpg->tport;
> > +
> > +	switch (tport->tport_proto_id) {
> > +	case SCSI_PROTOCOL_SAS:
> > +		return sas_get_pr_transport_id(se_tpg, se_nacl, pr_reg,
> > +					format_code, buf);
> > +	case SCSI_PROTOCOL_FCP:
> > +		return fc_get_pr_transport_id(se_tpg, se_nacl, pr_reg,
> > +					format_code, buf);
> > +	case SCSI_PROTOCOL_ISCSI:
> > +		return iscsi_get_pr_transport_id(se_tpg, se_nacl, pr_reg,
> > +					format_code, buf);
> > +	default:
> > +		pr_err("Unknown tport_proto_id: 0x%02x, using"
> > +			" SAS emulation\n", tport->tport_proto_id);
> > +		break;
> > +	}
> > +
> > +	return sas_get_pr_transport_id(se_tpg, se_nacl, pr_reg,
> > +			format_code, buf);
> > +}
> > +
> > +static u32 tcm_vhost_get_pr_transport_id_len(
> > +	struct se_portal_group *se_tpg,
> > +	struct se_node_acl *se_nacl,
> > +	struct t10_pr_registration *pr_reg,
> > +	int *format_code)
> > +{
> > +	struct tcm_vhost_tpg *tpg = container_of(se_tpg,
> > +				struct tcm_vhost_tpg, se_tpg);
> > +	struct tcm_vhost_tport *tport = tpg->tport;
> > +
> > +	switch (tport->tport_proto_id) {
> > +	case SCSI_PROTOCOL_SAS:
> > +		return sas_get_pr_transport_id_len(se_tpg, se_nacl, pr_reg,
> > +					format_code);
> > +	case SCSI_PROTOCOL_FCP:
> > +		return fc_get_pr_transport_id_len(se_tpg, se_nacl, pr_reg,
> > +					format_code);
> > +	case SCSI_PROTOCOL_ISCSI:
> > +		return iscsi_get_pr_transport_id_len(se_tpg, se_nacl, pr_reg,
> > +					format_code);
> > +	default:
> > +		pr_err("Unknown tport_proto_id: 0x%02x, using"
> > +			" SAS emulation\n", tport->tport_proto_id);
> > +		break;
> > +	}
> > +
> > +	return sas_get_pr_transport_id_len(se_tpg, se_nacl, pr_reg,
> > +			format_code);
> > +}
> > +
> > +static char *tcm_vhost_parse_pr_out_transport_id(
> > +	struct se_portal_group *se_tpg,
> > +	const char *buf,
> > +	u32 *out_tid_len,
> > +	char **port_nexus_ptr)
> > +{
> > +	struct tcm_vhost_tpg *tpg = container_of(se_tpg,
> > +				struct tcm_vhost_tpg, se_tpg);
> > +	struct tcm_vhost_tport *tport = tpg->tport;
> > +
> > +	switch (tport->tport_proto_id) {
> > +	case SCSI_PROTOCOL_SAS:
> > +		return sas_parse_pr_out_transport_id(se_tpg, buf, out_tid_len,
> > +					port_nexus_ptr);
> > +	case SCSI_PROTOCOL_FCP:
> > +		return fc_parse_pr_out_transport_id(se_tpg, buf, out_tid_len,
> > +					port_nexus_ptr);
> > +	case SCSI_PROTOCOL_ISCSI:
> > +		return iscsi_parse_pr_out_transport_id(se_tpg, buf, out_tid_len,
> > +					port_nexus_ptr);
> > +	default:
> > +		pr_err("Unknown tport_proto_id: 0x%02x, using"
> > +			" SAS emulation\n", tport->tport_proto_id);
> > +		break;
> > +	}
> > +
> > +	return sas_parse_pr_out_transport_id(se_tpg, buf, out_tid_len,
> > +			port_nexus_ptr);
> > +}
> > +
> > +static struct se_node_acl *tcm_vhost_alloc_fabric_acl(
> > +	struct se_portal_group *se_tpg)
> > +{
> > +	struct tcm_vhost_nacl *nacl;
> > +
> > +	nacl = kzalloc(sizeof(struct tcm_vhost_nacl), GFP_KERNEL);
> > +	if (!nacl) {
> > +		pr_err("Unable to alocate struct tcm_vhost_nacl\n");
> > +		return NULL;
> > +	}
> > +
> > +	return &nacl->se_node_acl;
> > +}
> > +
> > +static void tcm_vhost_release_fabric_acl(
> > +	struct se_portal_group *se_tpg,
> > +	struct se_node_acl *se_nacl)
> > +{
> > +	struct tcm_vhost_nacl *nacl = container_of(se_nacl,
> > +			struct tcm_vhost_nacl, se_node_acl);
> > +	kfree(nacl);
> > +}
> > +
> > +static u32 tcm_vhost_tpg_get_inst_index(struct se_portal_group *se_tpg)
> > +{
> > +	return 1;
> > +}
> > +
> > +static void tcm_vhost_release_cmd(struct se_cmd *se_cmd)
> > +{
> > +	return;
> > +}
> > +
> > +static int tcm_vhost_shutdown_session(struct se_session *se_sess)
> > +{
> > +	return 0;
> > +}
> > +
> > +static void tcm_vhost_close_session(struct se_session *se_sess)
> > +{
> > +	return;
> > +}
> > +
> > +static u32 tcm_vhost_sess_get_index(struct se_session *se_sess)
> > +{
> > +	return 0;
> > +}
> > +
> > +static int tcm_vhost_write_pending(struct se_cmd *se_cmd)
> > +{
> > +	/* Go ahead and process the write immediately */
> > +	target_execute_cmd(se_cmd);
> > +	return 0;
> > +}
> > +
> > +static int tcm_vhost_write_pending_status(struct se_cmd *se_cmd)
> > +{
> > +	return 0;
> > +}
> > +
> > +static void tcm_vhost_set_default_node_attrs(struct se_node_acl *nacl)
> > +{
> > +	return;
> > +}
> > +
> > +static u32 tcm_vhost_get_task_tag(struct se_cmd *se_cmd)
> > +{
> > +	return 0;
> > +}
> > +
> > +static int tcm_vhost_get_cmd_state(struct se_cmd *se_cmd)
> > +{
> > +	return 0;
> > +}
> > +
> > +static void vhost_scsi_complete_cmd(struct tcm_vhost_cmd *);
> 
> can we reorder code to avoid forward declarations?
> 

<nod>, moved vhost_scsi_complete_cmd() up here..

> > +
> > +static int tcm_vhost_queue_data_in(struct se_cmd *se_cmd)
> > +{
> > +	struct tcm_vhost_cmd *tv_cmd = container_of(se_cmd,
> > +				struct tcm_vhost_cmd, tvc_se_cmd);
> > +	vhost_scsi_complete_cmd(tv_cmd);
> > +	return 0;
> > +}
> > +
> > +static int tcm_vhost_queue_status(struct se_cmd *se_cmd)
> > +{
> > +	struct tcm_vhost_cmd *tv_cmd = container_of(se_cmd,
> > +				struct tcm_vhost_cmd, tvc_se_cmd);
> > +	vhost_scsi_complete_cmd(tv_cmd);
> > +	return 0;
> > +}
> > +
> > +static int tcm_vhost_queue_tm_rsp(struct se_cmd *se_cmd)
> > +{
> > +	return 0;
> > +}
> > +
> > +static u16 tcm_vhost_set_fabric_sense_len(struct se_cmd *se_cmd,
> > +	u32 sense_length)
> > +{
> > +	return 0;
> > +}
> > +
> > +static u16 tcm_vhost_get_fabric_sense_len(void)
> > +{
> > +	return 0;
> > +}
> > +
> > +static void vhost_scsi_free_cmd(struct tcm_vhost_cmd *tv_cmd)
> > +{
> > +	struct se_cmd *se_cmd = &tv_cmd->tvc_se_cmd;
> > +
> > +	/* TODO locking against target/backend threads? */
> > +	transport_generic_free_cmd(se_cmd, 1);
> > +
> > +	if (tv_cmd->tvc_sgl_count) {
> > +		u32 i;
> > +		for (i = 0; i < tv_cmd->tvc_sgl_count; i++)
> > +			put_page(sg_page(&tv_cmd->tvc_sgl[i]));
> > +
> > +		kfree(tv_cmd->tvc_sgl);
> > +	}
> > +
> > +	kfree(tv_cmd);
> > +}
> > +
> > +/* Dequeue a command from the completion list */
> > +static struct tcm_vhost_cmd *vhost_scsi_get_cmd_from_completion(
> > +	struct vhost_scsi *vs)
> > +{
> > +	struct tcm_vhost_cmd *tv_cmd = NULL;
> > +
> > +	spin_lock_bh(&vs->vs_completion_lock);
> > +	if (list_empty(&vs->vs_completion_list)) {
> > +		spin_unlock_bh(&vs->vs_completion_lock);
> > +		return NULL;
> > +	}
> > +
> > +	list_for_each_entry(tv_cmd, &vs->vs_completion_list,
> > +			    tvc_completion_list) {
> > +		list_del(&tv_cmd->tvc_completion_list);
> > +		break;
> > +	}
> > +	spin_unlock_bh(&vs->vs_completion_lock);
> > +	return tv_cmd;
> > +}
> > +
> > +/* Fill in status and signal that we are done processing this command
> > + *
> > + * This is scheduled in the vhost work queue so we are called with the owner
> > + * process mm and can access the vring.
> > + */
> > +static void vhost_scsi_complete_cmd_work(struct vhost_work *work)
> > +{
> > +	struct vhost_scsi *vs = container_of(work, struct vhost_scsi,
> > +					vs_completion_work);
> > +	struct tcm_vhost_cmd *tv_cmd;
> > +
> > +	while ((tv_cmd = vhost_scsi_get_cmd_from_completion(vs)) != NULL) {
> 
> I normally prefer while ((tv_cmd = vhost_scsi_get_cmd_from_completion(vs)))
> without != NULL
> 

Dropping the extra '!= NULL' conditional check here..

> > +		struct virtio_scsi_cmd_resp v_rsp;
> > +		struct se_cmd *se_cmd = &tv_cmd->tvc_se_cmd;
> > +		int ret;
> > +
> > +		pr_debug("%s tv_cmd %p resid %u status %#02x\n", __func__,
> > +			tv_cmd, se_cmd->residual_count, se_cmd->scsi_status);
> > +
> > +		memset(&v_rsp, 0, sizeof(v_rsp));
> > +		v_rsp.resid = se_cmd->residual_count;
> > +		/* TODO is status_qualifier field needed? */
> > +		v_rsp.status = se_cmd->scsi_status;
> > +		v_rsp.sense_len = se_cmd->scsi_sense_length;
> > +		memcpy(v_rsp.sense, tv_cmd->tvc_sense_buf,
> > +		       v_rsp.sense_len);
> > +		ret = copy_to_user(tv_cmd->tvc_resp, &v_rsp, sizeof(v_rsp));
> > +		if (likely(ret == 0))
> > +			vhost_add_used(&vs->vqs[2], tv_cmd->tvc_vq_desc, 0);
> > +		else
> > +			pr_err("Faulted on virtio_scsi_cmd_resp\n");
> > +
> > +		vhost_scsi_free_cmd(tv_cmd);
> > +	}
> > +
> > +	vhost_signal(&vs->dev, &vs->vqs[2]);
> > +}
> > +
> > +static void vhost_scsi_complete_cmd(struct tcm_vhost_cmd *tv_cmd)
> > +{
> > +	struct vhost_scsi *vs = tv_cmd->tvc_vhost;
> > +
> > +	pr_debug("%s tv_cmd %p\n", __func__, tv_cmd);
> 
> Is this doing something you can not already do with
> tracing? If all these pr_debug messages are useful,
> I think it's best to add a kconfig entry for them
> so that they are off for people even if they build
> debug kernels.
> 

So I ended up just dropping this particular noisemaker while moving
vhost_scsi_complete_cmd().

As for CONFIG_DYNAMIC_DEBUG=y usage, this is what we've used for target
core + fabric debug messages since the v3.1 days when Andy Grover did
the conversion in the old lio-core tree..

IHMO they are pretty nice to have when your helping someone to debug an
issue they are experiencing.  ;)

> > +
> > +	spin_lock_bh(&vs->vs_completion_lock);
> > +	list_add_tail(&tv_cmd->tvc_completion_list, &vs->vs_completion_list);
> > +	spin_unlock_bh(&vs->vs_completion_lock);
> > +
> > +	vhost_work_queue(&vs->dev, &vs->vs_completion_work);
> > +}
> > +
> > +static struct tcm_vhost_cmd *vhost_scsi_allocate_cmd(
> > +	struct tcm_vhost_tpg *tv_tpg,
> > +	struct virtio_scsi_cmd_req *v_req,
> > +	u32 exp_data_len,
> > +	int data_direction)
> > +{
> > +	struct tcm_vhost_cmd *tv_cmd;
> > +	struct tcm_vhost_nexus *tv_nexus;
> > +	struct se_portal_group *se_tpg = &tv_tpg->se_tpg;
> > +	struct se_session *se_sess;
> > +	struct se_cmd *se_cmd;
> > +	int sam_task_attr;
> > +
> > +	tv_nexus = tv_tpg->tpg_nexus;
> > +	if (!tv_nexus) {
> > +		pr_err("Unable to locate active struct tcm_vhost_nexus\n");
> > +		return ERR_PTR(-EIO);
> > +	}
> > +	se_sess = tv_nexus->tvn_se_sess;
> > +
> > +	tv_cmd = kzalloc(sizeof(struct tcm_vhost_cmd), GFP_ATOMIC);
> > +	if (!tv_cmd) {
> > +		pr_err("Unable to allocate struct tcm_vhost_cmd\n");
> > +		return ERR_PTR(-ENOMEM);
> > +	}
> > +	INIT_LIST_HEAD(&tv_cmd->tvc_completion_list);
> > +	tv_cmd->tvc_tag = v_req->tag;
> > +
> > +	se_cmd = &tv_cmd->tvc_se_cmd;
> > +	/*
> > +	 * Locate the SAM Task Attr from virtio_scsi_cmd_req
> > +	 */
> > +	sam_task_attr = v_req->task_attr;
> > +	/*
> > +	 * Initialize struct se_cmd descriptor from TCM infrastructure
> > +	 */
> > +	transport_init_se_cmd(se_cmd, se_tpg->se_tpg_tfo, se_sess, exp_data_len,
> > +				data_direction, sam_task_attr,
> > +				&tv_cmd->tvc_sense_buf[0]);
> > +
> > +#if 0	/* FIXME: vhost_scsi_allocate_cmd() BIDI operation */
> > +	if (bidi)
> > +		se_cmd->se_cmd_flags |= SCF_BIDI;
> > +#endif
> > +	return tv_cmd;
> > +}
> > +
> > +/*
> > + * Map a user memory range into a scatterlist
> > + *
> > + * Returns the number of scatterlist entries used or -errno on error.
> > + */
> > +static int vhost_scsi_map_to_sgl(struct scatterlist *sgl,
> > +	unsigned int sgl_count, void __user *ptr, size_t len, int write)
> > +{
> > +	struct scatterlist *sg = sgl;
> > +	unsigned int npages = 0;
> > +	int ret;
> > +
> > +	while (len > 0) {
> > +		struct page *page;
> > +		unsigned int offset = (uintptr_t)ptr & ~PAGE_MASK;
> > +		unsigned int nbytes = min_t(unsigned int,
> > +				PAGE_SIZE - offset, len);
> > +
> > +		if (npages == sgl_count) {
> > +			ret = -ENOBUFS;
> > +			goto err;
> > +		}
> > +
> > +		ret = get_user_pages_fast((unsigned long)ptr, 1, write, &page);
> > +		BUG_ON(ret == 0); /* we should either get our page or fail */
> > +		if (ret < 0)
> > +			goto err;
> > +
> > +		sg_set_page(sg, page, nbytes, offset);
> > +		ptr += nbytes;
> > +		len -= nbytes;
> > +		sg++;
> > +		npages++;
> > +	}
> > +	return npages;
> > +
> > +err:
> > +	/* Put pages that we hold */
> > +	for (sg = sgl; sg != &sgl[npages]; sg++)
> > +		put_page(sg_page(sg));
> > +	return ret;
> > +}
> > +
> > +static int vhost_scsi_map_iov_to_sgl(struct tcm_vhost_cmd *tv_cmd,
> > +	struct iovec *iov, unsigned int niov, int write)
> > +{
> > +	int ret;
> > +	unsigned int i;
> > +	u32 sgl_count;
> > +	struct scatterlist *sg;
> > +
> > +	/*
> > +	 * Find out how long sglist needs to be
> > +	 */
> > +	sgl_count = 0;
> > +	for (i = 0; i < niov; i++) {
> > +		sgl_count += (((uintptr_t)iov[i].iov_base + iov[i].iov_len +
> > +				PAGE_SIZE - 1) >> PAGE_SHIFT) -
> > +				((uintptr_t)iov[i].iov_base >> PAGE_SHIFT);
> > +	}
> > +	/* TODO overflow checking */
> > +
> > +	sg = kmalloc(sizeof(tv_cmd->tvc_sgl[0]) * sgl_count, GFP_ATOMIC);
> > +	if (!sg)
> > +		return -ENOMEM;
> > +	pr_debug("%s sg %p sgl_count %u is_err %ld\n", __func__,
> > +	       sg, sgl_count, IS_ERR(sg));
> > +	sg_init_table(sg, sgl_count);
> > +
> > +	tv_cmd->tvc_sgl = sg;
> > +	tv_cmd->tvc_sgl_count = sgl_count;
> > +
> > +	pr_debug("Mapping %u iovecs for %u pages\n", niov, sgl_count);
> > +	for (i = 0; i < niov; i++) {
> > +		ret = vhost_scsi_map_to_sgl(sg, sgl_count, iov[i].iov_base,
> > +					iov[i].iov_len, write);
> > +		if (ret < 0) {
> > +			for (i = 0; i < tv_cmd->tvc_sgl_count; i++)
> > +				put_page(sg_page(&tv_cmd->tvc_sgl[i]));
> > +			kfree(tv_cmd->tvc_sgl);
> > +			tv_cmd->tvc_sgl = NULL;
> > +			tv_cmd->tvc_sgl_count = 0;
> > +			return ret;
> > +		}
> > +
> > +		sg += ret;
> > +		sgl_count -= ret;
> > +	}
> > +	return 0;
> > +}
> > +
> > +static void tcm_vhost_submission_work(struct work_struct *work)
> > +{
> > +	struct tcm_vhost_cmd *tv_cmd =
> > +		container_of(work, struct tcm_vhost_cmd, work);
> > +	struct se_cmd *se_cmd = &tv_cmd->tvc_se_cmd;
> > +	struct scatterlist *sg_ptr, *sg_bidi_ptr = NULL;
> > +	int rc, sg_no_bidi = 0;
> > +	/*
> > +	 * Locate the struct se_lun pointer based on v_req->lun, and
> > +	 * attach it to struct se_cmd
> > +	 */
> > +	rc = transport_lookup_cmd_lun(&tv_cmd->tvc_se_cmd, tv_cmd->tvc_lun);
> > +	if (rc < 0) {
> > +		pr_err("Failed to look up lun: %d\n", tv_cmd->tvc_lun);
> > +		transport_send_check_condition_and_sense(&tv_cmd->tvc_se_cmd,
> > +			tv_cmd->tvc_se_cmd.scsi_sense_reason, 0);
> > +		transport_generic_free_cmd(se_cmd, 0);
> > +		return;
> > +	}
> > +
> > +	rc = target_setup_cmd_from_cdb(se_cmd, tv_cmd->tvc_cdb);
> > +	if (rc == -ENOMEM) {
> > +		transport_send_check_condition_and_sense(se_cmd,
> > +				TCM_LOGICAL_UNIT_COMMUNICATION_FAILURE, 0);
> > +		transport_generic_free_cmd(se_cmd, 0);
> > +		return;
> > +	} else if (rc < 0) {
> > +		if (se_cmd->se_cmd_flags & SCF_SCSI_RESERVATION_CONFLICT)
> > +			tcm_vhost_queue_status(se_cmd);
> > +		else
> > +			transport_send_check_condition_and_sense(se_cmd,
> > +					se_cmd->scsi_sense_reason, 0);
> > +		transport_generic_free_cmd(se_cmd, 0);
> > +		return;
> > +	}
> > +
> > +	if (tv_cmd->tvc_sgl_count) {
> > +		sg_ptr = tv_cmd->tvc_sgl;
> > +		/*
> > +		 * For BIDI commands, pass in the extra READ buffer
> > +		 * to transport_generic_map_mem_to_cmd() below..
> > +		 */
> > +/* FIXME: Fix BIDI operation in tcm_vhost_submission_work() */
> > +#if 0
> > +		if (se_cmd->se_cmd_flags & SCF_BIDI) {
> > +			sg_bidi_ptr = NULL;
> > +			sg_no_bidi = 0;
> > +		}
> > +#endif
> > +	} else {
> > +		sg_ptr = NULL;
> > +	}
> > +
> > +	rc = transport_generic_map_mem_to_cmd(se_cmd, sg_ptr,
> > +				tv_cmd->tvc_sgl_count, sg_bidi_ptr,
> > +				sg_no_bidi);
> > +	if (rc < 0) {
> > +		transport_send_check_condition_and_sense(se_cmd,
> > +				se_cmd->scsi_sense_reason, 0);
> > +		transport_generic_free_cmd(se_cmd, 0);
> > +		return;
> > +	}
> > +	transport_handle_cdb_direct(se_cmd);
> > +}
> > +
> > +static void vhost_scsi_handle_vq(struct vhost_scsi *vs)
> > +{
> > +	struct vhost_virtqueue *vq = &vs->vqs[2];
> > +	struct virtio_scsi_cmd_req v_req;
> > +	struct tcm_vhost_tpg *tv_tpg;
> > +	struct tcm_vhost_cmd *tv_cmd;
> > +	u32 exp_data_len, data_first, data_num, data_direction;
> > +	unsigned out, in, i;
> > +	int head, ret;
> > +
> > +	/* Must use ioctl VHOST_SCSI_SET_ENDPOINT */
> > +	tv_tpg = vs->vs_tpg;
> > +	if (unlikely(!tv_tpg)) {
> > +		pr_err("%s endpoint not set\n", __func__);
> > +		return;
> > +	}
> > +
> > +	mutex_lock(&vq->mutex);
> > +	vhost_disable_notify(&vs->dev, vq);
> > +
> > +	for (;;) {
> > +		head = vhost_get_vq_desc(&vs->dev, vq, vq->iov,
> > +					ARRAY_SIZE(vq->iov), &out, &in,
> > +					NULL, NULL);
> > +		pr_debug("vhost_get_vq_desc: head: %d, out: %u in: %u\n",
> > +					head, out, in);
> > +		/* On error, stop handling until the next kick. */
> > +		if (unlikely(head < 0))
> > +			break;
> > +		/* Nothing new?  Wait for eventfd to tell us they refilled. */
> > +		if (head == vq->num) {
> > +			if (unlikely(vhost_enable_notify(&vs->dev, vq))) {
> > +				vhost_disable_notify(&vs->dev, vq);
> > +				continue;
> > +			}
> > +			break;
> > +		}
> > +
> > +/* FIXME: BIDI operation */
> > +		if (out == 1 && in == 1) {
> > +			data_direction = DMA_NONE;
> > +			data_first = 0;
> > +			data_num = 0;
> > +		} else if (out == 1 && in > 1) {
> > +			data_direction = DMA_FROM_DEVICE;
> > +			data_first = out + 1;
> > +			data_num = in - 1;
> > +		} else if (out > 1 && in == 1) {
> > +			data_direction = DMA_TO_DEVICE;
> > +			data_first = 1;
> > +			data_num = out - 1;
> > +		} else {
> > +			vq_err(vq, "Invalid buffer layout out: %u in: %u\n",
> > +					out, in);
> > +			break;
> > +		}
> > +
> > +		/*
> > +		 * Check for a sane resp buffer so we can report errors to
> > +		 * the guest.
> > +		 */
> > +		if (unlikely(vq->iov[out].iov_len !=
> > +					sizeof(struct virtio_scsi_cmd_resp))) {
> > +			vq_err(vq, "Expecting virtio_scsi_cmd_resp, got %zu"
> > +				" bytes\n", vq->iov[out].iov_len);
> > +			break;
> > +		}
> > +
> > +		if (unlikely(vq->iov[0].iov_len != sizeof(v_req))) {
> > +			vq_err(vq, "Expecting virtio_scsi_cmd_req, got %zu"
> > +				" bytes\n", vq->iov[0].iov_len);
> > +			break;
> > +		}
> > +		pr_debug("Calling __copy_from_user: vq->iov[0].iov_base: %p,"
> > +			" len: %zu\n", vq->iov[0].iov_base, sizeof(v_req));
> > +		ret = __copy_from_user(&v_req, vq->iov[0].iov_base,
> > +				sizeof(v_req));
> > +		if (unlikely(ret)) {
> > +			vq_err(vq, "Faulted on virtio_scsi_cmd_req\n");
> > +			break;
> > +		}
> > +
> > +		exp_data_len = 0;
> > +		for (i = 0; i < data_num; i++)
> > +			exp_data_len += vq->iov[data_first + i].iov_len;
> > +
> > +		tv_cmd = vhost_scsi_allocate_cmd(tv_tpg, &v_req,
> > +					exp_data_len, data_direction);
> > +		if (IS_ERR(tv_cmd)) {
> > +			vq_err(vq, "vhost_scsi_allocate_cmd failed %ld\n",
> > +					PTR_ERR(tv_cmd));
> > +			break;
> > +		}
> > +		pr_debug("Allocated tv_cmd: %p exp_data_len: %d, data_direction"
> > +			": %d\n", tv_cmd, exp_data_len, data_direction);
> > +
> > +		tv_cmd->tvc_vhost = vs;
> > +
> > +		if (unlikely(vq->iov[out].iov_len !=
> > +				sizeof(struct virtio_scsi_cmd_resp))) {
> > +			vq_err(vq, "Expecting virtio_scsi_cmd_resp, got %zu"
> > +				" bytes, out: %d, in: %d\n",
> > +				vq->iov[out].iov_len, out, in);
> > +			break;
> > +		}
> > +
> > +		tv_cmd->tvc_resp = vq->iov[out].iov_base;
> > +
> > +		/*
> > +		 * Copy in the recieved CDB descriptor into tv_cmd->tvc_cdb
> > +		 * that will be used by tcm_vhost_new_cmd_map() and down into
> > +		 * target_setup_cmd_from_cdb()
> > +		 */
> > +		memcpy(tv_cmd->tvc_cdb, v_req.cdb, TCM_VHOST_MAX_CDB_SIZE);
> > +		/*
> > +		 * Check that the recieved CDB size does not exceeded our
> > +		 * hardcoded max for tcm_vhost
> > +		 */
> > +		/* TODO what if cdb was too small for varlen cdb header? */
> > +		if (unlikely(scsi_command_size(tv_cmd->tvc_cdb) >
> > +					TCM_VHOST_MAX_CDB_SIZE)) {
> > +			vq_err(vq, "Received SCSI CDB with command_size: %d that"
> > +				" exceeds SCSI_MAX_VARLEN_CDB_SIZE: %d\n",
> > +				scsi_command_size(tv_cmd->tvc_cdb),
> > +				TCM_VHOST_MAX_CDB_SIZE);
> > +			break; /* TODO */
> > +		}
> > +		tv_cmd->tvc_lun = ((v_req.lun[2] << 8) | v_req.lun[3]) & 0x3FFF;
> > +
> > +		pr_debug("vhost_scsi got command opcode: %#02x, lun: %d\n",
> > +			tv_cmd->tvc_cdb[0], tv_cmd->tvc_lun);
> > +
> > +		if (data_direction != DMA_NONE) {
> > +			ret = vhost_scsi_map_iov_to_sgl(tv_cmd,
> > +					&vq->iov[data_first], data_num,
> > +					data_direction == DMA_TO_DEVICE);
> > +			if (unlikely(ret)) {
> > +				vq_err(vq, "Failed to map iov to sgl\n");
> > +				break; /* TODO */
> > +			}
> > +		}
> > +
> > +		/*
> > +		 * Save the descriptor from vhost_get_vq_desc() to be used to
> > +		 * complete the virtio-scsi request in TCM callback context via
> > +		 * tcm_vhost_queue_data_in() and tcm_vhost_queue_status()
> > +		 */
> > +		tv_cmd->tvc_vq_desc = head;
> > +		/*
> > +		 * Dispatch tv_cmd descriptor for cmwq execution in process
> > +		 * context provided by tcm_vhost_workqueue.  This also ensures
> > +		 * tv_cmd is executed on the same kworker CPU as this vhost
> > +		 * thread to gain positive L2 cache locality effects..
> > +		 */
> > +		INIT_WORK(&tv_cmd->work, tcm_vhost_submission_work);
> > +		queue_work(tcm_vhost_workqueue, &tv_cmd->work);
> > +	}
> > +
> > +	mutex_unlock(&vq->mutex);
> > +}
> > +
> > +static void vhost_scsi_ctl_handle_kick(struct vhost_work *work)
> > +{
> > +	pr_err("%s: The handling func for control queue.\n", __func__);
> > +}
> > +
> > +static void vhost_scsi_evt_handle_kick(struct vhost_work *work)
> > +{
> > +	pr_err("%s: The handling func for event queue.\n", __func__);
> > +}
> > +
> 
> can userspace still trigger these? If not pls add a comment explaining
> why are above never triggering.
> 

Yes, they are both triggered via userspace once as the virtio-scsi
enabled guest boots.

Also, changing these from pr_err -> pr_debug..

> > +static void vhost_scsi_handle_kick(struct vhost_work *work)
> > +{
> > +	struct vhost_virtqueue *vq = container_of(work, struct vhost_virtqueue,
> > +						poll.work);
> > +	struct vhost_scsi *vs = container_of(vq->dev, struct vhost_scsi, dev);
> > +
> > +	vhost_scsi_handle_vq(vs);
> > +}
> > +
> > +/*
> > + * Called from vhost_scsi_ioctl() context to walk the list of available
> > + * tcm_vhost_tpg with an active struct tcm_vhost_nexus
> > + */
> > +static int vhost_scsi_set_endpoint(
> > +	struct vhost_scsi *vs,
> > +	struct vhost_scsi_target *t)
> > +{
> > +	struct tcm_vhost_tport *tv_tport;
> > +	struct tcm_vhost_tpg *tv_tpg;
> > +	int index;
> > +
> > +	mutex_lock(&vs->dev.mutex);
> > +	/* Verify that ring has been setup correctly. */
> > +	for (index = 0; index < vs->dev.nvqs; ++index) {
> > +		/* Verify that ring has been setup correctly. */
> > +		if (!vhost_vq_access_ok(&vs->vqs[index])) {
> > +			mutex_unlock(&vs->dev.mutex);
> > +			return -EFAULT;
> > +		}
> > +	}
> > +
> > +	if (vs->vs_tpg) {
> > +		mutex_unlock(&vs->dev.mutex);
> > +		return -EEXIST;
> > +	}
> > +	mutex_unlock(&vs->dev.mutex);
> 
> vs->vs_tpg can change at this point and be != NULL in loop below. Not an issue?
> 

Mmmm, your right, and I don't think it is correct..

I think the right thing is to moving the 'if (vs->vs_tpg)' check down in
the vs->dev.mutex protected area before doing the vs->vs_tpg = tv_tpg
assignment..

> > +	mutex_lock(&tcm_vhost_mutex);
> > +	list_for_each_entry(tv_tpg, &tcm_vhost_list, tv_tpg_list) {
> 
> If you move this loop to a function, then it can use goto to cleanup on error.
> 

I've just inlined the one error case here in the loop..

> > +		mutex_lock(&tv_tpg->tv_tpg_mutex);
> > +		if (!tv_tpg->tpg_nexus) {
> > +			mutex_unlock(&tv_tpg->tv_tpg_mutex);
> > +			continue;
> > +		}
> > +		if (atomic_read(&tv_tpg->tv_tpg_vhost_count)) {
> > +			mutex_unlock(&tv_tpg->tv_tpg_mutex);
> > +			continue;
> > +		}
> > +		tv_tport = tv_tpg->tport;
> > +
> > +		if (!strcmp(tv_tport->tport_name, t->vhost_wwpn) &&
> > +		    (tv_tpg->tport_tpgt == t->vhost_tpgt)) {
> > +			atomic_inc(&tv_tpg->tv_tpg_vhost_count);
> > +			smp_mb__after_atomic_inc();
> 
> this an other uses of memory barriers need a comment: what are we
> flushing out and why.  Also - could something like kref be used for
> reference counting? If this is not datapath this might be better.
> 

Actually, ->tpg_vhost_count is always protected by ->tv_tpg_mutex, so
for this case it's unnecessary..  Changing this to a non atomic_t type
now..

Doing the same for ->tv_tpg_port_count, and obtaining/release
->tv_tpg_mutex in tcm_vhost_port_*link() as well..

> > +			mutex_unlock(&tv_tpg->tv_tpg_mutex);
> > +			mutex_unlock(&tcm_vhost_mutex);
> > +
> > +			mutex_lock(&vs->dev.mutex);
> > +			vs->vs_tpg = tv_tpg;
> > +			atomic_inc(&vs->vhost_ref_cnt);

Also, vhost_scsi->vhost_ref_cnt doesn't appear to be used aside from
this location (it's never decremented), and AFAICT it's not necessary.

Dropping this for now at well, unless then is an objection from Stefan
as to why it's needed..

> > +			smp_mb__after_atomic_inc();
> > +			mutex_unlock(&vs->dev.mutex);
> > +			return 0;
> > +		}
> > +		mutex_unlock(&tv_tpg->tv_tpg_mutex);
> > +	}
> > +	mutex_unlock(&tcm_vhost_mutex);
> > +	return -EINVAL;
> > +}
> > +
> > +static int vhost_scsi_clear_endpoint(
> > +	struct vhost_scsi *vs,
> > +	struct vhost_scsi_target *t)
> > +{
> > +	struct tcm_vhost_tport *tv_tport;
> > +	struct tcm_vhost_tpg *tv_tpg;
> > +	int index;
> > +
> > +	mutex_lock(&vs->dev.mutex);
> > +	/* Verify that ring has been setup correctly. */
> > +	for (index = 0; index < vs->dev.nvqs; ++index) {
> > +		if (!vhost_vq_access_ok(&vs->vqs[index])) {
> > +			mutex_unlock(&vs->dev.mutex);
> > +			return -EFAULT;
> > +		}
> > +	}
> > +
> > +	if (!vs->vs_tpg) {
> > +		mutex_unlock(&vs->dev.mutex);
> > +		return -ENODEV;
> > +	}
> > +	tv_tpg = vs->vs_tpg;
> > +	tv_tport = tv_tpg->tport;
> > +
> > +	if (strcmp(tv_tport->tport_name, t->vhost_wwpn) ||
> > +	    (tv_tpg->tport_tpgt != t->vhost_tpgt)) {
> > +		mutex_unlock(&vs->dev.mutex);
> > +		pr_warn("tv_tport->tport_name: %s, tv_tpg->tport_tpgt: %hu"
> > +			" does not match t->vhost_wwpn: %s, t->vhost_tpgt: %hu\n",
> > +			tv_tport->tport_name, tv_tpg->tport_tpgt,
> > +			t->vhost_wwpn, t->vhost_tpgt);
> > +		return -EINVAL;
> > +	}
> > +	atomic_dec(&tv_tpg->tv_tpg_vhost_count);
> > +	vs->vs_tpg = NULL;
> > +	mutex_unlock(&vs->dev.mutex);
> > +
> > +	return 0;
> 
> We could do it like this:
> 
> 	err:
> 		mutex_unlock(&vs->dev.mutex);
> 		return ret;
> 
> to make it clear we do not exit this with lock taken
> 

<nod>, Added err: label for vhost_scsi_clear_endpoint error path

> > +}
> > +
> > +static int vhost_scsi_open(struct inode *inode, struct file *f)
> > +{
> > +	struct vhost_scsi *s;
> > +	int r;
> > +
> > +	s = kzalloc(sizeof(*s), GFP_KERNEL);
> > +	if (!s)
> > +		return -ENOMEM;
> > +
> > +	vhost_work_init(&s->vs_completion_work, vhost_scsi_complete_cmd_work);
> > +	INIT_LIST_HEAD(&s->vs_completion_list);
> > +	spin_lock_init(&s->vs_completion_lock);
> > +
> > +	s->vqs[0].handle_kick = vhost_scsi_ctl_handle_kick;
> > +	s->vqs[1].handle_kick = vhost_scsi_evt_handle_kick;
> > +	s->vqs[2].handle_kick = vhost_scsi_handle_kick;
> 
> better to add an enum with VQ numbers.
> 

<nod>, adding the following + updated usage in vhost_scsi_open()

enum {
        VHOST_SCSI_VQ_CTL = 0,
        VHOST_SCSI_VQ_EVT = 1,
        VHOST_SCSI_VQ_IO = 2,
};

> > +	r = vhost_dev_init(&s->dev, s->vqs, 3);
> > +	if (r < 0) {
> > +		kfree(s);
> > +		return r;
> > +	}
> > +
> > +	f->private_data = s;
> > +	return 0;
> > +}
> > +
> > +static int vhost_scsi_release(struct inode *inode, struct file *f)
> > +{
> > +	struct vhost_scsi *s = f->private_data;
> > +
> > +	if (s->vs_tpg && s->vs_tpg->tport) {
> > +		struct vhost_scsi_target backend;
> > +
> > +		memcpy(backend.vhost_wwpn, s->vs_tpg->tport->tport_name,
> > +				sizeof(backend.vhost_wwpn));
> > +		backend.vhost_tpgt = s->vs_tpg->tport_tpgt;
> > +		vhost_scsi_clear_endpoint(s, &backend);
> > +	}
> > +
> > +	vhost_dev_cleanup(&s->dev, false);
> > +	kfree(s);
> > +	return 0;
> > +}
> > +
> > +static int vhost_scsi_set_features(struct vhost_scsi *vs, u64 features)
> > +{
> > +	if (features & ~VHOST_FEATURES)
> > +		return -EOPNOTSUPP;
> > +
> > +	mutex_lock(&vs->dev.mutex);
> > +	if ((features & (1 << VHOST_F_LOG_ALL)) &&
> > +	    !vhost_log_access_ok(&vs->dev)) {
> > +		mutex_unlock(&vs->dev.mutex);
> > +		return -EFAULT;
> > +	}
> > +	vs->dev.acked_features = features;
> > +	/* TODO possibly smp_wmb() and flush vqs */
> 
> Either that or fail if already running.
> Current userspace does not change features once set,
> but it's cleaner not to make assumptions.
> 

Ok, following what drivers/vhost/net.c does, how about the following..?

Add the basic vhost_scsi_flush() primative:

static void vhost_scsi_flush_vq(struct vhost_scsi *vs, int index)
{
        vhost_poll_flush(&vs->dev.vqs[index].poll);
}

static void vhost_scsi_flush(struct vhost_scsi *s)
{
        vhost_scsi_flush_vq(s, VHOST_SCSI_VQ_CTL);
        vhost_scsi_flush_vq(s, VHOST_SCSI_VQ_EVT);
        vhost_scsi_flush_vq(s, VHOST_SCSI_VQ_IO);
}

And update the set_features:

@@ -967,7 +980,8 @@ static int vhost_scsi_set_features(struct vhost_scsi *vs, u64 features)
                return -EFAULT;
        }
        vs->dev.acked_features = features;
-       /* TODO possibly smp_wmb() and flush vqs */
+       smp_wmb();
+       vhost_scsi_flush(vs);
        mutex_unlock(&vs->dev.mutex);
        return 0;
 }

> > +	mutex_unlock(&vs->dev.mutex);
> > +	return 0;
> > +}
> > +
> > +static long vhost_scsi_ioctl(struct file *f, unsigned int ioctl,
> > +				unsigned long arg)
> > +{
> > +	struct vhost_scsi *vs = f->private_data;
> > +	struct vhost_scsi_target backend;
> > +	void __user *argp = (void __user *)arg;
> > +	u64 __user *featurep = argp;
> > +	u64 features;
> > +	int r;
> > +
> > +	switch (ioctl) {
> > +	case VHOST_SCSI_SET_ENDPOINT:
> > +		if (copy_from_user(&backend, argp, sizeof backend))
> > +			return -EFAULT;
> > +
> > +		return vhost_scsi_set_endpoint(vs, &backend);
> > +	case VHOST_SCSI_CLEAR_ENDPOINT:
> > +		if (copy_from_user(&backend, argp, sizeof backend))
> > +			return -EFAULT;
> > +
> > +		return vhost_scsi_clear_endpoint(vs, &backend);
> > +	case VHOST_SCSI_GET_ABI_VERSION:
> > +		if (copy_from_user(&backend, argp, sizeof backend))
> > +			return -EFAULT;
> 
> Why are we reading this in BTW?
> 

Dropping the unnecessary copy_from_user() usage here..

> > +
> > +		backend.abi_version = VHOST_SCSI_ABI_VERSION;
> > +
> > +		if (copy_to_user(argp, &backend, sizeof backend))
> > +			return -EFAULT;
> > +		return 0;
> > +	case VHOST_GET_FEATURES:
> > +		features = VHOST_FEATURES;
> > +		if (copy_to_user(featurep, &features, sizeof features))
> > +			return -EFAULT;
> > +		return 0;
> > +	case VHOST_SET_FEATURES:
> > +		if (copy_from_user(&features, featurep, sizeof features))
> > +			return -EFAULT;
> > +		return vhost_scsi_set_features(vs, features);
> > +	default:
> > +		mutex_lock(&vs->dev.mutex);
> > +		r = vhost_dev_ioctl(&vs->dev, ioctl, arg);
> > +		mutex_unlock(&vs->dev.mutex);
> > +		return r;
> > +	}
> > +}
> > +
> > +static const struct file_operations vhost_scsi_fops = {
> > +	.owner          = THIS_MODULE,
> > +	.release        = vhost_scsi_release,
> > +	.unlocked_ioctl = vhost_scsi_ioctl,
> > +	/* TODO compat ioctl? */
> 
> well?
> 

<nod>, adding the missing compat ioctl handling now..

> > +	.open           = vhost_scsi_open,
> > +	.llseek		= noop_llseek,
> > +};
> > +
> > +static struct miscdevice vhost_scsi_misc = {
> > +	MISC_DYNAMIC_MINOR,
> > +	"vhost-scsi",
> > +	&vhost_scsi_fops,
> > +};
> > +
> > +static int __init vhost_scsi_register(void)
> > +{
> > +	return misc_register(&vhost_scsi_misc);
> > +}
> > +
> > +static int vhost_scsi_deregister(void)
> > +{
> > +	return misc_deregister(&vhost_scsi_misc);
> > +}
> > +
> > +static char *tcm_vhost_dump_proto_id(struct tcm_vhost_tport *tport)
> > +{
> > +	switch (tport->tport_proto_id) {
> > +	case SCSI_PROTOCOL_SAS:
> > +		return "SAS";
> > +	case SCSI_PROTOCOL_FCP:
> > +		return "FCP";
> > +	case SCSI_PROTOCOL_ISCSI:
> > +		return "iSCSI";
> > +	default:
> > +		break;
> > +	}
> > +
> > +	return "Unknown";
> > +}
> > +
> > +static int tcm_vhost_port_link(
> > +	struct se_portal_group *se_tpg,
> > +	struct se_lun *lun)
> 
> I'd like this and other places to be like this:
>  static int tcm_vhost_port_link(struct se_portal_group *se_tpg,
>  	struct se_lun *lun)
> 
> or
>  static int
>  tcm_vhost_port_link(struct se_portal_group *se_tpg,
> 		     struct se_lun *lun)
> 
> so that it's more like the rest of vhost code.
> 

<nod>, doing the former for all of the places that do not exceed 80
characters..

> 
> > +{
> > +	struct tcm_vhost_tpg *tv_tpg = container_of(se_tpg,
> > +				struct tcm_vhost_tpg, se_tpg);
> > +
> > +	atomic_inc(&tv_tpg->tv_tpg_port_count);
> > +	smp_mb__after_atomic_inc();
> > +
> > +	return 0;
> > +}
> > +
> > +static void tcm_vhost_port_unlink(
> > +	struct se_portal_group *se_tpg,
> > +	struct se_lun *se_lun)
> > +{
> > +	struct tcm_vhost_tpg *tv_tpg = container_of(se_tpg,
> > +				struct tcm_vhost_tpg, se_tpg);
> > +
> > +	atomic_dec(&tv_tpg->tv_tpg_port_count);
> > +	smp_mb__after_atomic_dec();
> > +}
> > +
> > +static struct se_node_acl *tcm_vhost_make_nodeacl(
> > +	struct se_portal_group *se_tpg,
> > +	struct config_group *group,
> > +	const char *name)
> > +{
> > +	struct se_node_acl *se_nacl, *se_nacl_new;
> > +	struct tcm_vhost_nacl *nacl;
> > +	u64 wwpn = 0;
> > +	u32 nexus_depth;
> > +
> > +	/* tcm_vhost_parse_wwn(name, &wwpn, 1) < 0)
> > +		return ERR_PTR(-EINVAL); */
> > +	se_nacl_new = tcm_vhost_alloc_fabric_acl(se_tpg);
> > +	if (!se_nacl_new)
> > +		return ERR_PTR(-ENOMEM);
> > +
> > +	nexus_depth = 1;
> > +	/*
> > +	 * se_nacl_new may be released by core_tpg_add_initiator_node_acl()
> > +	 * when converting a NodeACL from demo mode -> explict
> > +	 */
> > +	se_nacl = core_tpg_add_initiator_node_acl(se_tpg, se_nacl_new,
> > +				name, nexus_depth);
> > +	if (IS_ERR(se_nacl)) {
> > +		tcm_vhost_release_fabric_acl(se_tpg, se_nacl_new);
> > +		return se_nacl;
> > +	}
> > +	/*
> > +	 * Locate our struct tcm_vhost_nacl and set the FC Nport WWPN
> > +	 */
> > +	nacl = container_of(se_nacl, struct tcm_vhost_nacl, se_node_acl);
> > +	nacl->iport_wwpn = wwpn;
> > +
> > +	return se_nacl;
> > +}
> > +
> > +static void tcm_vhost_drop_nodeacl(struct se_node_acl *se_acl)
> > +{
> > +	struct tcm_vhost_nacl *nacl = container_of(se_acl,
> > +				struct tcm_vhost_nacl, se_node_acl);
> > +	core_tpg_del_initiator_node_acl(se_acl->se_tpg, se_acl, 1);
> > +	kfree(nacl);
> > +}
> > +
> > +static int tcm_vhost_make_nexus(
> > +	struct tcm_vhost_tpg *tv_tpg,
> > +	const char *name)
> > +{
> > +	struct se_portal_group *se_tpg;
> > +	struct tcm_vhost_nexus *tv_nexus;
> > +
> > +	mutex_lock(&tv_tpg->tv_tpg_mutex);
> > +	if (tv_tpg->tpg_nexus) {
> > +		mutex_unlock(&tv_tpg->tv_tpg_mutex);
> > +		pr_debug("tv_tpg->tpg_nexus already exists\n");
> > +		return -EEXIST;
> > +	}
> > +	se_tpg = &tv_tpg->se_tpg;
> > +
> > +	tv_nexus = kzalloc(sizeof(struct tcm_vhost_nexus), GFP_KERNEL);
> > +	if (!tv_nexus) {
> > +		mutex_unlock(&tv_tpg->tv_tpg_mutex);
> > +		pr_err("Unable to allocate struct tcm_vhost_nexus\n");
> > +		return -ENOMEM;
> > +	}
> > +	/*
> > +	 *  Initialize the struct se_session pointer
> > +	 */
> > +	tv_nexus->tvn_se_sess = transport_init_session();
> > +	if (IS_ERR(tv_nexus->tvn_se_sess)) {
> > +		mutex_unlock(&tv_tpg->tv_tpg_mutex);
> > +		kfree(tv_nexus);
> > +		return -ENOMEM;
> > +	}
> > +	/*
> > +	 * Since we are running in 'demo mode' this call with generate a
> > +	 * struct se_node_acl for the tcm_vhost struct se_portal_group with
> > +	 * the SCSI Initiator port name of the passed configfs group 'name'.
> > +	 */
> > +	tv_nexus->tvn_se_sess->se_node_acl = core_tpg_check_initiator_node_acl(
> > +				se_tpg, (unsigned char *)name);
> > +	if (!tv_nexus->tvn_se_sess->se_node_acl) {
> > +		mutex_unlock(&tv_tpg->tv_tpg_mutex);
> > +		pr_debug("core_tpg_check_initiator_node_acl() failed"
> > +				" for %s\n", name);
> > +		transport_free_session(tv_nexus->tvn_se_sess);
> > +		kfree(tv_nexus);
> > +		return -ENOMEM;
> > +	}
> > +	/*
> > +	 * Now register the TCM vHost virtual I_T Nexus as active with the
> 
> I think s/vHost/vhost/ would be nice :)
> 

Done

> > +	 * call to __transport_register_session()
> > +	 */
> > +	__transport_register_session(se_tpg, tv_nexus->tvn_se_sess->se_node_acl,
> > +			tv_nexus->tvn_se_sess, tv_nexus);
> > +	tv_tpg->tpg_nexus = tv_nexus;
> > +
> > +	mutex_unlock(&tv_tpg->tv_tpg_mutex);
> > +	return 0;
> > +}
> > +
> > +static int tcm_vhost_drop_nexus(
> > +	struct tcm_vhost_tpg *tpg)
> > +{
> > +	struct se_session *se_sess;
> > +	struct tcm_vhost_nexus *tv_nexus;
> > +
> > +	mutex_lock(&tpg->tv_tpg_mutex);
> > +	tv_nexus = tpg->tpg_nexus;
> > +	if (!tv_nexus) {
> > +		mutex_unlock(&tpg->tv_tpg_mutex);
> > +		return -ENODEV;
> > +	}
> > +
> > +	se_sess = tv_nexus->tvn_se_sess;
> > +	if (!se_sess) {
> > +		mutex_unlock(&tpg->tv_tpg_mutex);
> > +		return -ENODEV;
> > +	}
> > +
> > +	if (atomic_read(&tpg->tv_tpg_port_count)) {
> > +		mutex_unlock(&tpg->tv_tpg_mutex);
> > +		pr_err("Unable to remove TCM_vHost I_T Nexus with"
> > +			" active TPG port count: %d\n",
> > +			atomic_read(&tpg->tv_tpg_port_count));
> > +		return -EPERM;
> 
> EBUSY?
> 
> 

Fixed

> > +	}
> > +
> > +	if (atomic_read(&tpg->tv_tpg_vhost_count)) {
> > +		mutex_unlock(&tpg->tv_tpg_mutex);
> > +		pr_err("Unable to remove TCM_vHost I_T Nexus with"
> > +			" active TPG vhost count: %d\n",
> > +			atomic_read(&tpg->tv_tpg_vhost_count));
> > +		return -EPERM;
> 
> Same?
> 

Fixed

> > +	}
> > +
> > +	pr_debug("TCM_vHost_ConfigFS: Removing I_T Nexus to emulated"
> > +		" %s Initiator Port: %s\n", tcm_vhost_dump_proto_id(tpg->tport),
> > +		tv_nexus->tvn_se_sess->se_node_acl->initiatorname);
> > +	/*
> > +	 * Release the SCSI I_T Nexus to the emulated vHost Target Port
> > +	 */
> > +	transport_deregister_session(tv_nexus->tvn_se_sess);
> > +	tpg->tpg_nexus = NULL;
> > +	mutex_unlock(&tpg->tv_tpg_mutex);
> > +
> > +	kfree(tv_nexus);
> > +	return 0;
> > +}
> > +
> > +static ssize_t tcm_vhost_tpg_show_nexus(
> > +	struct se_portal_group *se_tpg,
> > +	char *page)
> > +{
> > +	struct tcm_vhost_tpg *tv_tpg = container_of(se_tpg,
> > +				struct tcm_vhost_tpg, se_tpg);
> > +	struct tcm_vhost_nexus *tv_nexus;
> > +	ssize_t ret;
> > +
> > +	mutex_lock(&tv_tpg->tv_tpg_mutex);
> > +	tv_nexus = tv_tpg->tpg_nexus;
> > +	if (!tv_nexus) {
> > +		mutex_unlock(&tv_tpg->tv_tpg_mutex);
> > +		return -ENODEV;
> > +	}
> > +	ret = snprintf(page, PAGE_SIZE, "%s\n",
> > +			tv_nexus->tvn_se_sess->se_node_acl->initiatorname);
> > +	mutex_unlock(&tv_tpg->tv_tpg_mutex);
> > +
> > +	return ret;
> > +}
> > +
> > +static ssize_t tcm_vhost_tpg_store_nexus(
> > +	struct se_portal_group *se_tpg,
> > +	const char *page,
> > +	size_t count)
> > +{
> > +	struct tcm_vhost_tpg *tv_tpg = container_of(se_tpg,
> > +				struct tcm_vhost_tpg, se_tpg);
> > +	struct tcm_vhost_tport *tport_wwn = tv_tpg->tport;
> > +	unsigned char i_port[TCM_VHOST_NAMELEN], *ptr, *port_ptr;
> > +	int ret;
> > +	/*
> > +	 * Shutdown the active I_T nexus if 'NULL' is passed..
> > +	 */
> > +	if (!strncmp(page, "NULL", 4)) {
> > +		ret = tcm_vhost_drop_nexus(tv_tpg);
> > +		return (!ret) ? count : ret;
> > +	}
> > +	/*
> > +	 * Otherwise make sure the passed virtual Initiator port WWN matches
> > +	 * the fabric protocol_id set in tcm_vhost_make_tport(), and call
> > +	 * tcm_vhost_make_nexus().
> > +	 */
> > +	if (strlen(page) >= TCM_VHOST_NAMELEN) {
> > +		pr_err("Emulated NAA Sas Address: %s, exceeds"
> > +				" max: %d\n", page, TCM_VHOST_NAMELEN);
> > +		return -EINVAL;
> > +	}
> > +	snprintf(&i_port[0], TCM_VHOST_NAMELEN, "%s", page);
> > +
> > +	ptr = strstr(i_port, "naa.");
> > +	if (ptr) {
> > +		if (tport_wwn->tport_proto_id != SCSI_PROTOCOL_SAS) {
> > +			pr_err("Passed SAS Initiator Port %s does not"
> > +				" match target port protoid: %s\n", i_port,
> > +				tcm_vhost_dump_proto_id(tport_wwn));
> > +			return -EINVAL;
> > +		}
> > +		port_ptr = &i_port[0];
> > +		goto check_newline;
> > +	}
> > +	ptr = strstr(i_port, "fc.");
> > +	if (ptr) {
> > +		if (tport_wwn->tport_proto_id != SCSI_PROTOCOL_FCP) {
> > +			pr_err("Passed FCP Initiator Port %s does not"
> > +				" match target port protoid: %s\n", i_port,
> > +				tcm_vhost_dump_proto_id(tport_wwn));
> > +			return -EINVAL;
> > +		}
> > +		port_ptr = &i_port[3]; /* Skip over "fc." */
> > +		goto check_newline;
> > +	}
> > +	ptr = strstr(i_port, "iqn.");
> > +	if (ptr) {
> > +		if (tport_wwn->tport_proto_id != SCSI_PROTOCOL_ISCSI) {
> > +			pr_err("Passed iSCSI Initiator Port %s does not"
> > +				" match target port protoid: %s\n", i_port,
> > +				tcm_vhost_dump_proto_id(tport_wwn));
> > +			return -EINVAL;
> > +		}
> > +		port_ptr = &i_port[0];
> > +		goto check_newline;
> > +	}
> > +	pr_err("Unable to locate prefix for emulated Initiator Port:"
> > +			" %s\n", i_port);
> > +	return -EINVAL;
> > +	/*
> > +	 * Clear any trailing newline for the NAA WWN
> > +	 */
> > +check_newline:
> > +	if (i_port[strlen(i_port)-1] == '\n')
> > +		i_port[strlen(i_port)-1] = '\0';
> > +
> > +	ret = tcm_vhost_make_nexus(tv_tpg, port_ptr);
> > +	if (ret < 0)
> > +		return ret;
> > +
> > +	return count;
> > +}
> > +
> > +TF_TPG_BASE_ATTR(tcm_vhost, nexus, S_IRUGO | S_IWUSR);
> > +
> > +static struct configfs_attribute *tcm_vhost_tpg_attrs[] = {
> > +	&tcm_vhost_tpg_nexus.attr,
> > +	NULL,
> > +};
> > +
> > +static struct se_portal_group *tcm_vhost_make_tpg(
> > +	struct se_wwn *wwn,
> > +	struct config_group *group,
> > +	const char *name)
> > +{
> > +	struct tcm_vhost_tport *tport = container_of(wwn,
> > +			struct tcm_vhost_tport, tport_wwn);
> > +
> > +	struct tcm_vhost_tpg *tpg;
> > +	unsigned long tpgt;
> > +	int ret;
> > +
> > +	if (strstr(name, "tpgt_") != name)
> > +		return ERR_PTR(-EINVAL);
> > +	if (kstrtoul(name + 5, 10, &tpgt) || tpgt > UINT_MAX)
> > +		return ERR_PTR(-EINVAL);
> > +
> > +	tpg = kzalloc(sizeof(struct tcm_vhost_tpg), GFP_KERNEL);
> > +	if (!tpg) {
> > +		pr_err("Unable to allocate struct tcm_vhost_tpg");
> > +		return ERR_PTR(-ENOMEM);
> > +	}
> > +	mutex_init(&tpg->tv_tpg_mutex);
> > +	INIT_LIST_HEAD(&tpg->tv_tpg_list);
> > +	tpg->tport = tport;
> > +	tpg->tport_tpgt = tpgt;
> > +
> > +	ret = core_tpg_register(&tcm_vhost_fabric_configfs->tf_ops, wwn,
> > +				&tpg->se_tpg, tpg, TRANSPORT_TPG_TYPE_NORMAL);
> > +	if (ret < 0) {
> > +		kfree(tpg);
> > +		return NULL;
> > +	}
> > +	mutex_lock(&tcm_vhost_mutex);
> > +	list_add_tail(&tpg->tv_tpg_list, &tcm_vhost_list);
> > +	mutex_unlock(&tcm_vhost_mutex);
> > +
> > +	return &tpg->se_tpg;
> > +}
> > +
> > +static void tcm_vhost_drop_tpg(struct se_portal_group *se_tpg)
> > +{
> > +	struct tcm_vhost_tpg *tpg = container_of(se_tpg,
> > +				struct tcm_vhost_tpg, se_tpg);
> > +
> > +	mutex_lock(&tcm_vhost_mutex);
> > +	list_del(&tpg->tv_tpg_list);
> > +	mutex_unlock(&tcm_vhost_mutex);
> > +	/*
> > +	 * Release the virtual I_T Nexus for this vHost TPG
> > +	 */
> > +	tcm_vhost_drop_nexus(tpg);
> > +	/*
> > +	 * Deregister the se_tpg from TCM..
> > +	 */
> > +	core_tpg_deregister(se_tpg);
> > +	kfree(tpg);
> > +}
> > +
> > +static struct se_wwn *tcm_vhost_make_tport(
> > +	struct target_fabric_configfs *tf,
> > +	struct config_group *group,
> > +	const char *name)
> > +{
> > +	struct tcm_vhost_tport *tport;
> > +	char *ptr;
> > +	u64 wwpn = 0;
> > +	int off = 0;
> > +
> > +	/* if (tcm_vhost_parse_wwn(name, &wwpn, 1) < 0)
> > +		return ERR_PTR(-EINVAL); */
> > +
> > +	tport = kzalloc(sizeof(struct tcm_vhost_tport), GFP_KERNEL);
> > +	if (!tport) {
> > +		pr_err("Unable to allocate struct tcm_vhost_tport");
> > +		return ERR_PTR(-ENOMEM);
> > +	}
> > +	tport->tport_wwpn = wwpn;
> > +	/*
> > +	 * Determine the emulated Protocol Identifier and Target Port Name
> > +	 * based on the incoming configfs directory name.
> > +	 */
> > +	ptr = strstr(name, "naa.");
> > +	if (ptr) {
> > +		tport->tport_proto_id = SCSI_PROTOCOL_SAS;
> > +		goto check_len;
> > +	}
> > +	ptr = strstr(name, "fc.");
> > +	if (ptr) {
> > +		tport->tport_proto_id = SCSI_PROTOCOL_FCP;
> > +		off = 3; /* Skip over "fc." */
> > +		goto check_len;
> > +	}
> > +	ptr = strstr(name, "iqn.");
> > +	if (ptr) {
> > +		tport->tport_proto_id = SCSI_PROTOCOL_ISCSI;
> > +		goto check_len;
> > +	}
> > +
> > +	pr_err("Unable to locate prefix for emulated Target Port:"
> > +			" %s\n", name);
> > +	kfree(tport);
> > +	return ERR_PTR(-EINVAL);
> > +
> > +check_len:
> > +	if (strlen(name) >= TCM_VHOST_NAMELEN) {
> > +		pr_err("Emulated %s Address: %s, exceeds"
> > +			" max: %d\n", name, tcm_vhost_dump_proto_id(tport),
> > +			TCM_VHOST_NAMELEN);
> > +		kfree(tport);
> > +		return ERR_PTR(-EINVAL);
> > +	}
> > +	snprintf(&tport->tport_name[0], TCM_VHOST_NAMELEN, "%s", &name[off]);
> > +
> > +	pr_debug("TCM_VHost_ConfigFS: Allocated emulated Target"
> > +		" %s Address: %s\n", tcm_vhost_dump_proto_id(tport), name);
> > +
> > +	return &tport->tport_wwn;
> > +}
> > +
> > +static void tcm_vhost_drop_tport(struct se_wwn *wwn)
> > +{
> > +	struct tcm_vhost_tport *tport = container_of(wwn,
> > +				struct tcm_vhost_tport, tport_wwn);
> > +
> > +	pr_debug("TCM_VHost_ConfigFS: Deallocating emulated Target"
> > +		" %s Address: %s\n", tcm_vhost_dump_proto_id(tport),
> > +		tport->tport_name);
> > +
> > +	kfree(tport);
> > +}
> > +
> > +static ssize_t tcm_vhost_wwn_show_attr_version(
> > +	struct target_fabric_configfs *tf,
> > +	char *page)
> > +{
> > +	return sprintf(page, "TCM_VHOST fabric module %s on %s/%s"
> > +		"on "UTS_RELEASE"\n", TCM_VHOST_VERSION, utsname()->sysname,
> > +		utsname()->machine);
> > +}
> > +
> > +TF_WWN_ATTR_RO(tcm_vhost, version);
> > +
> > +static struct configfs_attribute *tcm_vhost_wwn_attrs[] = {
> > +	&tcm_vhost_wwn_version.attr,
> > +	NULL,
> > +};
> > +
> > +static struct target_core_fabric_ops tcm_vhost_ops = {
> > +	.get_fabric_name		= tcm_vhost_get_fabric_name,
> > +	.get_fabric_proto_ident		= tcm_vhost_get_fabric_proto_ident,
> > +	.tpg_get_wwn			= tcm_vhost_get_fabric_wwn,
> > +	.tpg_get_tag			= tcm_vhost_get_tag,
> > +	.tpg_get_default_depth		= tcm_vhost_get_default_depth,
> > +	.tpg_get_pr_transport_id	= tcm_vhost_get_pr_transport_id,
> > +	.tpg_get_pr_transport_id_len	= tcm_vhost_get_pr_transport_id_len,
> > +	.tpg_parse_pr_out_transport_id	= tcm_vhost_parse_pr_out_transport_id,
> > +	.tpg_check_demo_mode		= tcm_vhost_check_true,
> > +	.tpg_check_demo_mode_cache	= tcm_vhost_check_true,
> > +	.tpg_check_demo_mode_write_protect = tcm_vhost_check_false,
> > +	.tpg_check_prod_mode_write_protect = tcm_vhost_check_false,
> > +	.tpg_alloc_fabric_acl		= tcm_vhost_alloc_fabric_acl,
> > +	.tpg_release_fabric_acl		= tcm_vhost_release_fabric_acl,
> > +	.tpg_get_inst_index		= tcm_vhost_tpg_get_inst_index,
> > +	.release_cmd			= tcm_vhost_release_cmd,
> > +	.shutdown_session		= tcm_vhost_shutdown_session,
> > +	.close_session			= tcm_vhost_close_session,
> > +	.sess_get_index			= tcm_vhost_sess_get_index,
> > +	.sess_get_initiator_sid		= NULL,
> > +	.write_pending			= tcm_vhost_write_pending,
> > +	.write_pending_status		= tcm_vhost_write_pending_status,
> > +	.set_default_node_attributes	= tcm_vhost_set_default_node_attrs,
> > +	.get_task_tag			= tcm_vhost_get_task_tag,
> > +	.get_cmd_state			= tcm_vhost_get_cmd_state,
> > +	.queue_data_in			= tcm_vhost_queue_data_in,
> > +	.queue_status			= tcm_vhost_queue_status,
> > +	.queue_tm_rsp			= tcm_vhost_queue_tm_rsp,
> > +	.get_fabric_sense_len		= tcm_vhost_get_fabric_sense_len,
> > +	.set_fabric_sense_len		= tcm_vhost_set_fabric_sense_len,
> > +	/*
> > +	 * Setup callers for generic logic in target_core_fabric_configfs.c
> > +	 */
> > +	.fabric_make_wwn		= tcm_vhost_make_tport,
> > +	.fabric_drop_wwn		= tcm_vhost_drop_tport,
> > +	.fabric_make_tpg		= tcm_vhost_make_tpg,
> > +	.fabric_drop_tpg		= tcm_vhost_drop_tpg,
> > +	.fabric_post_link		= tcm_vhost_port_link,
> > +	.fabric_pre_unlink		= tcm_vhost_port_unlink,
> > +	.fabric_make_np			= NULL,
> > +	.fabric_drop_np			= NULL,
> > +	.fabric_make_nodeacl		= tcm_vhost_make_nodeacl,
> > +	.fabric_drop_nodeacl		= tcm_vhost_drop_nodeacl,
> > +};
> > +
> > +static int tcm_vhost_register_configfs(void)
> > +{
> > +	struct target_fabric_configfs *fabric;
> > +	int ret;
> > +
> > +	pr_debug("TCM_VHOST fabric module %s on %s/%s"
> > +		" on "UTS_RELEASE"\n", TCM_VHOST_VERSION, utsname()->sysname,
> > +		utsname()->machine);
> > +	/*
> > +	 * Register the top level struct config_item_type with TCM core
> > +	 */
> > +	fabric = target_fabric_configfs_init(THIS_MODULE, "vhost");
> > +	if (IS_ERR(fabric)) {
> > +		pr_err("target_fabric_configfs_init() failed\n");
> > +		return PTR_ERR(fabric);
> > +	}
> > +	/*
> > +	 * Setup fabric->tf_ops from our local tcm_vhost_ops
> > +	 */
> > +	fabric->tf_ops = tcm_vhost_ops;
> > +	/*
> > +	 * Setup default attribute lists for various fabric->tf_cit_tmpl
> > +	 */
> > +	TF_CIT_TMPL(fabric)->tfc_wwn_cit.ct_attrs = tcm_vhost_wwn_attrs;
> > +	TF_CIT_TMPL(fabric)->tfc_tpg_base_cit.ct_attrs = tcm_vhost_tpg_attrs;
> > +	TF_CIT_TMPL(fabric)->tfc_tpg_attrib_cit.ct_attrs = NULL;
> > +	TF_CIT_TMPL(fabric)->tfc_tpg_param_cit.ct_attrs = NULL;
> > +	TF_CIT_TMPL(fabric)->tfc_tpg_np_base_cit.ct_attrs = NULL;
> > +	TF_CIT_TMPL(fabric)->tfc_tpg_nacl_base_cit.ct_attrs = NULL;
> > +	TF_CIT_TMPL(fabric)->tfc_tpg_nacl_attrib_cit.ct_attrs = NULL;
> > +	TF_CIT_TMPL(fabric)->tfc_tpg_nacl_auth_cit.ct_attrs = NULL;
> > +	TF_CIT_TMPL(fabric)->tfc_tpg_nacl_param_cit.ct_attrs = NULL;
> > +	/*
> > +	 * Register the fabric for use within TCM
> > +	 */
> > +	ret = target_fabric_configfs_register(fabric);
> > +	if (ret < 0) {
> > +		pr_err("target_fabric_configfs_register() failed"
> > +				" for TCM_VHOST\n");
> > +		return ret;
> > +	}
> > +	/*
> > +	 * Setup our local pointer to *fabric
> > +	 */
> > +	tcm_vhost_fabric_configfs = fabric;
> > +	pr_debug("TCM_VHOST[0] - Set fabric -> tcm_vhost_fabric_configfs\n");
> > +	return 0;
> > +};
> > +
> > +static void tcm_vhost_deregister_configfs(void)
> > +{
> > +	if (!tcm_vhost_fabric_configfs)
> > +		return;
> > +
> > +	target_fabric_configfs_deregister(tcm_vhost_fabric_configfs);
> > +	tcm_vhost_fabric_configfs = NULL;
> > +	pr_debug("TCM_VHOST[0] - Cleared tcm_vhost_fabric_configfs\n");
> > +};
> > +
> > +static int __init tcm_vhost_init(void)
> > +{
> > +	int ret = -ENOMEM;
> > +
> > +	tcm_vhost_workqueue = alloc_workqueue("tcm_vhost", 0, 0);
> > +	if (!tcm_vhost_workqueue)
> > +		goto out;
> 
> Pls add a comment explaining why we need our own workqueue
> and aren't using the system one instead.
> 

<nod>, loopback + tcm_qla2xxx use their own dedicated workqueue(s) as
well..

> > +
> > +	ret = vhost_scsi_register();
> > +	if (ret < 0)
> > +		goto out_destroy_workqueue;
> > +
> > +	ret = tcm_vhost_register_configfs();
> > +	if (ret < 0)
> > +		goto out_vhost_scsi_deregister;
> > +
> > +	return 0;
> > +
> > +out_vhost_scsi_deregister:
> > +	vhost_scsi_deregister();
> > +out_destroy_workqueue:
> > +	destroy_workqueue(tcm_vhost_workqueue);
> > +out:
> > +	return ret;
> > +};
> > +
> > +static void tcm_vhost_exit(void)
> > +{
> > +	tcm_vhost_deregister_configfs();
> > +	vhost_scsi_deregister();
> > +	destroy_workqueue(tcm_vhost_workqueue);
> > +};
> > +
> > +MODULE_DESCRIPTION("TCM_VHOST series fabric driver");
> > +MODULE_LICENSE("GPL");
> > +module_init(tcm_vhost_init);
> > +module_exit(tcm_vhost_exit);
> > diff --git a/drivers/vhost/tcm_vhost.h b/drivers/vhost/tcm_vhost.h
> > new file mode 100644
> > index 0000000..c983ed2
> > --- /dev/null
> > +++ b/drivers/vhost/tcm_vhost.h
> > @@ -0,0 +1,101 @@
> > +#define TCM_VHOST_VERSION  "v0.1"
> > +#define TCM_VHOST_NAMELEN 256
> > +#define TCM_VHOST_MAX_CDB_SIZE 32
> > +
> > +struct tcm_vhost_cmd {
> > +	/* Descriptor from vhost_get_vq_desc() for virt_queue segment */
> > +	int tvc_vq_desc;
> > +	/* The Tag from include/linux/virtio_scsi.h:struct virtio_scsi_cmd_req */
> > +	u64 tvc_tag;
> > +	/* The number of scatterlists associated with this cmd */
> > +	u32 tvc_sgl_count;
> > +	/* Saved unpacked SCSI LUN for tcm_vhost_submission_work() */
> > +	u32 tvc_lun;
> > +	/* Pointer to the SGL formatted memory from virtio-scsi */
> > +	struct scatterlist *tvc_sgl;
> > +	/* Pointer to response */
> > +	struct virtio_scsi_cmd_resp __user *tvc_resp;
> > +	/* Pointer to vhost_scsi for our device */
> > +	struct vhost_scsi *tvc_vhost;
> > +	/* The TCM I/O descriptor that is accessed via container_of() */
> > +	struct se_cmd tvc_se_cmd;
> > +	/* work item used for cmwq dispatch to tcm_vhost_submission_work() */
> > +	struct work_struct work;
> > +	/* Copy of the incoming SCSI command descriptor block (CDB) */
> > +	unsigned char tvc_cdb[TCM_VHOST_MAX_CDB_SIZE];
> > +	/* Sense buffer that will be mapped into outgoing status */
> > +	unsigned char tvc_sense_buf[TRANSPORT_SENSE_BUFFER];
> > +	/* Completed commands list, serviced from vhost worker thread */
> > +	struct list_head tvc_completion_list;
> > +};
> > +
> > +struct tcm_vhost_nexus {
> > +	/* Pointer to TCM session for I_T Nexus */
> > +	struct se_session *tvn_se_sess;
> > +};
> > +
> > +struct tcm_vhost_nacl {
> > +	/* Binary World Wide unique Port Name for Vhost Initiator port */
> > +	u64 iport_wwpn;
> > +	/* ASCII formatted WWPN for Sas Initiator port */
> > +	char iport_name[TCM_VHOST_NAMELEN];
> > +	/* Returned by tcm_vhost_make_nodeacl() */
> > +	struct se_node_acl se_node_acl;
> > +};
> > +
> > +struct tcm_vhost_tpg {
> > +	/* Vhost port target portal group tag for TCM */
> > +	u16 tport_tpgt;
> > +	/* Used to track number of TPG Port/Lun Links wrt to explict I_T Nexus shutdown */
> > +	atomic_t tv_tpg_port_count;
> > +	/* Used for vhost_scsi device reference to tpg_nexus */
> > +	atomic_t tv_tpg_vhost_count;
> > +	/* list for tcm_vhost_list */
> > +	struct list_head tv_tpg_list;
> > +	/* Used to protect access for tpg_nexus */
> > +	struct mutex tv_tpg_mutex;
> 
> would it be easier to just use dev mutex instead?
> 
> > +	/* Pointer to the TCM VHost I_T Nexus for this TPG endpoint */
> > +	struct tcm_vhost_nexus *tpg_nexus;
> > +	/* Pointer back to tcm_vhost_tport */
> > +	struct tcm_vhost_tport *tport;
> > +	/* Returned by tcm_vhost_make_tpg() */
> > +	struct se_portal_group se_tpg;
> > +};
> > +
> > +struct tcm_vhost_tport {
> > +	/* SCSI protocol the tport is providing */
> > +	u8 tport_proto_id;
> > +	/* Binary World Wide unique Port Name for Vhost Target port */
> > +	u64 tport_wwpn;
> > +	/* ASCII formatted WWPN for Vhost Target port */
> > +	char tport_name[TCM_VHOST_NAMELEN];
> > +	/* Returned by tcm_vhost_make_tport() */
> > +	struct se_wwn tport_wwn;
> > +};
> > +
> > +/*
> > + * As per request from MST, keep TCM_VHOST related ioctl defines out of
> > + * linux/vhost.h (user-space) for now..
> > + */
> > +
> > +#include <linux/vhost.h>
> > +
> > +/*
> > + * Used by QEMU userspace to ensure a consistent vhost-scsi ABI.
> > + *
> > + * ABI Rev 0: July 2012 version starting point for v3.6-rc merge candidate +
> > + *            RFC-v2 vhost-scsi userspace.  Add GET_ABI_VERSION ioctl usage
> > + */
> > +
> > +#define VHOST_SCSI_ABI_VERSION	0
> > +
> > +struct vhost_scsi_target {
> > +	int abi_version;
> > +	unsigned char vhost_wwpn[TRANSPORT_IQN_LEN];
> > +	unsigned short vhost_tpgt;
> > +};
> > +
> > +/* VHOST_SCSI specific defines */
> > +#define VHOST_SCSI_SET_ENDPOINT _IOW(VHOST_VIRTIO, 0x40, struct vhost_scsi_target)
> > +#define VHOST_SCSI_CLEAR_ENDPOINT _IOW(VHOST_VIRTIO, 0x41, struct vhost_scsi_target)
> > +#define VHOST_SCSI_GET_ABI_VERSION _IOW(VHOST_VIRTIO, 0x42, struct vhost_scsi_target)
> 
> CLEAR_ENDPOINT and SET_ENDPOINT commands get an abi version
> too but it's ignored there. Intentional?
> 

Not quite..

> 
> Why not
> #define VHOST_SCSI_GET_ABI_VERSION _IOW(VHOST_VIRTIO, 0x42, int)
> and then you avoid changing vhost_scsi_target ...
> 

Ah yes, sorry, that makes alot more sense..  Changing GET_ABI_VERSION
to return 'int abi_version' to userspace now.

(As you may have noticed, I gave up ioctls for configfs for doing
compatible control plane code w/ python code a long time ago..  ;)

> 
> Also, let's add a comment like
> 
> /* Changing this breaks userspace. */
> 
> so we remember never to change this value.
> 

<nod>

On Thu, Jul 26, 2012 at 4:43 PM, Nicholas A. Bellinger
<nab@linux-iscsi.org>wrote:

> [...]
> +static void vhost_scsi_handle_vq(struct vhost_scsi *vs)
> +{
> +       struct vhost_virtqueue *vq = &vs->vqs[2];
> +       struct virtio_scsi_cmd_req v_req;
> +       struct tcm_vhost_tpg *tv_tpg;
> +       struct tcm_vhost_cmd *tv_cmd;
> +       u32 exp_data_len, data_first, data_num, data_direction;
> +       unsigned out, in, i;
> +       int head, ret;
> +
> +       /* Must use ioctl VHOST_SCSI_SET_ENDPOINT */
> +       tv_tpg = vs->vs_tpg;
> +       if (unlikely(!tv_tpg)) {
> +               pr_err("%s endpoint not set\n", __func__);
> +               return;
> +       }
> +
> +       mutex_lock(&vq->mutex);
> +       vhost_disable_notify(&vs->dev, vq);
> +
> +       for (;;) {
> +               head = vhost_get_vq_desc(&vs->dev, vq, vq->iov,
> +                                       ARRAY_SIZE(vq->iov), &out, &in,
> +                                       NULL, NULL);
> +               pr_debug("vhost_get_vq_desc: head: %d, out: %u in: %u\n",
> +                                       head, out, in);
> +               /* On error, stop handling until the next kick. */
> +               if (unlikely(head < 0))
> +                       break;
> +               /* Nothing new?  Wait for eventfd to tell us they
> refilled. */
> +               if (head == vq->num) {
> +                       if (unlikely(vhost_enable_notify(&vs->dev, vq))) {
> +                               vhost_disable_notify(&vs->dev, vq);
> +                               continue;
> +                       }
> +                       break;
> +               }
> +
> +/* FIXME: BIDI operation */
> +               if (out == 1 && in == 1) {
>

It seems to me like this is not the way that virtio devices are supposed to
behave - if a guest splits a virtio_scsi_cmd_req or _resp across a page
boundary, then this code won't work.

Quoting the 'Message Framing' part of the virtio spec:

"In particular, no implementation should use the descriptor boundaries to
determine the size of any header in a request. "


+                       data_direction = DMA_NONE;
> +                       data_first = 0;
> +                       data_num = 0;
> +               } else if (out == 1 && in > 1) {
> +                       data_direction = DMA_FROM_DEVICE;
> +                       data_first = out + 1;
> +                       data_num = in - 1;
> +               } else if (out > 1 && in == 1) {
> +                       data_direction = DMA_TO_DEVICE;
> +                       data_first = 1;
> +                       data_num = out - 1;
> +               } else {
> +                       vq_err(vq, "Invalid buffer layout out: %u in:
> %u\n",
> +                                       out, in);
> +                       break;
> +               }
> +
> +               /*
> +                * Check for a sane resp buffer so we can report errors to
> +                * the guest.
> +                */
> +               if (unlikely(vq->iov[out].iov_len !=
> +                                       sizeof(struct
> virtio_scsi_cmd_resp))) {
> +                       vq_err(vq, "Expecting virtio_scsi_cmd_resp, got
> %zu"
> +                               " bytes\n", vq->iov[out].iov_len);
> +                       break;
> +               }
> +
> +               if (unlikely(vq->iov[0].iov_len != sizeof(v_req))) {
> +                       vq_err(vq, "Expecting virtio_scsi_cmd_req, got %zu"
> +                               " bytes\n", vq->iov[0].iov_len);
> +                       break;
> +               }
> +               pr_debug("Calling __copy_from_user: vq->iov[0].iov_base:
> %p,"
> +                       " len: %zu\n", vq->iov[0].iov_base, sizeof(v_req));
> +               ret = __copy_from_user(&v_req, vq->iov[0].iov_base,
> +                               sizeof(v_req));
> +               if (unlikely(ret)) {
> +                       vq_err(vq, "Faulted on virtio_scsi_cmd_req\n");
> +                       break;
> +               }
> +
> +               exp_data_len = 0;
> +               for (i = 0; i < data_num; i++)
> +                       exp_data_len += vq->iov[data_first + i].iov_len;
> +
> +               tv_cmd = vhost_scsi_allocate_cmd(tv_tpg, &v_req,
> +                                       exp_data_len, data_direction);
> +               if (IS_ERR(tv_cmd)) {
> +                       vq_err(vq, "vhost_scsi_allocate_cmd failed %ld\n",
> +                                       PTR_ERR(tv_cmd));
> +                       break;
> +               }
> +               pr_debug("Allocated tv_cmd: %p exp_data_len: %d,
> data_direction"
> +                       ": %d\n", tv_cmd, exp_data_len, data_direction);
> +
> +               tv_cmd->tvc_vhost = vs;
> +
> +               if (unlikely(vq->iov[out].iov_len !=
> +                               sizeof(struct virtio_scsi_cmd_resp))) {
> +                       vq_err(vq, "Expecting virtio_scsi_cmd_resp, got
> %zu"
> +                               " bytes, out: %d, in: %d\n",
> +                               vq->iov[out].iov_len, out, in);
> +                       break;
> +               }
> +
> +               tv_cmd->tvc_resp = vq->iov[out].iov_base;
> +
> +               /*
> +                * Copy in the recieved CDB descriptor into tv_cmd->tvc_cdb
> +                * that will be used by tcm_vhost_new_cmd_map() and down
> into
> +                * target_setup_cmd_from_cdb()
> +                */
> +               memcpy(tv_cmd->tvc_cdb, v_req.cdb, TCM_VHOST_MAX_CDB_SIZE);
> +               /*
> +                * Check that the recieved CDB size does not exceeded our
> +                * hardcoded max for tcm_vhost
> +                */
> +               /* TODO what if cdb was too small for varlen cdb header? */
> +               if (unlikely(scsi_command_size(tv_cmd->tvc_cdb) >
> +                                       TCM_VHOST_MAX_CDB_SIZE)) {
> +                       vq_err(vq, "Received SCSI CDB with command_size:
> %d that"
> +                               " exceeds SCSI_MAX_VARLEN_CDB_SIZE: %d\n",
> +                               scsi_command_size(tv_cmd->tvc_cdb),
> +                               TCM_VHOST_MAX_CDB_SIZE);
> +                       break; /* TODO */
> +               }
> +               tv_cmd->tvc_lun = ((v_req.lun[2] << 8) | v_req.lun[3]) &
> 0x3FFF;
> +
> +               pr_debug("vhost_scsi got command opcode: %#02x, lun: %d\n",
> +                       tv_cmd->tvc_cdb[0], tv_cmd->tvc_lun);
> +
> +               if (data_direction != DMA_NONE) {
> +                       ret = vhost_scsi_map_iov_to_sgl(tv_cmd,
> +                                       &vq->iov[data_first], data_num,
> +                                       data_direction == DMA_TO_DEVICE);
> +                       if (unlikely(ret)) {
> +                               vq_err(vq, "Failed to map iov to sgl\n");
> +                               break; /* TODO */
> +                       }
> +               }
> +
> +               /*
> +                * Save the descriptor from vhost_get_vq_desc() to be used
> to
> +                * complete the virtio-scsi request in TCM callback
> context via
> +                * tcm_vhost_queue_data_in() and tcm_vhost_queue_status()
> +                */
> +               tv_cmd->tvc_vq_desc = head;
> +               /*
> +                * Dispatch tv_cmd descriptor for cmwq execution in process
> +                * context provided by tcm_vhost_workqueue.  This also
> ensures
> +                * tv_cmd is executed on the same kworker CPU as this vhost
> +                * thread to gain positive L2 cache locality effects..
> +                */
> +               INIT_WORK(&tv_cmd->work, tcm_vhost_submission_work);
> +               queue_work(tcm_vhost_workqueue, &tv_cmd->work);
> +       }
> +
> +       mutex_unlock(&vq->mutex);
> +}
> [...]
> --
> To unsubscribe from this list: send the line "unsubscribe kvm" in
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> More majordomo info at  http://vger.kernel.org/majordomo-info.html
>

Il 31/07/2012 22:52, Eric Northup ha scritto:
> It seems to me like this is not the way that virtio devices are supposed
> to behave - if a guest splits a virtio_scsi_cmd_req or _resp across a
> page boundary, then this code won't work.

Buffers can cover several pages.  Of course, data buffers have to be at
least sector aligned, but this restriction does not apply to
request/response descriptors.

> Quoting the 'Message Framing' part of the virtio spec:
> 
> "In particular, no implementation should use the descriptor boundaries
> to determine the size of any header in a request. "

True,  but this has never matched reality.

Paolo