[v2,1/3] hw/i2c: add mctp core

From: Klaus Jensen <k.jensen@samsung.com>

Add an abstract MCTP over I2C endpoint model. This implements MCTP
control message handling as well as handling the actual I2C transport
(packetization).

Devices are intended to derive from this and implement the class
methods.

Parts of this implementation is inspired by code[1] previously posted by
Jonathan Cameron.

  [1]: https://lore.kernel.org/qemu-devel/20220520170128.4436-1-Jonathan.Cameron@huawei.com/

Signed-off-by: Klaus Jensen <k.jensen@samsung.com>
---
 MAINTAINERS                   |   7 +
 hw/arm/Kconfig                |   1 +
 hw/i2c/Kconfig                |   4 +
 hw/i2c/mctp.c                 | 352 ++++++++++++++++++++++++++++++++++
 hw/i2c/meson.build            |   1 +
 hw/i2c/smbus_master.c         |  28 +++
 hw/i2c/trace-events           |  12 ++
 include/hw/i2c/mctp.h         | 114 +++++++++++
 include/hw/i2c/smbus_master.h |   3 +
 include/net/mctp.h            |  43 +++++
 10 files changed, 565 insertions(+)
 create mode 100644 hw/i2c/mctp.c
 create mode 100644 include/hw/i2c/mctp.h
 create mode 100644 include/net/mctp.h

On Tue, Apr 25, 2023 at 08:35:38AM +0200, Klaus Jensen wrote:
> From: Klaus Jensen <k.jensen@samsung.com>
> 
> Add an abstract MCTP over I2C endpoint model. This implements MCTP
> control message handling as well as handling the actual I2C transport
> (packetization).
> 
> Devices are intended to derive from this and implement the class
> methods.
> 
> Parts of this implementation is inspired by code[1] previously posted by
> Jonathan Cameron.

All in all this looks good.  Two comments:

I would like to see the buffer handling consolidated into one function
and the length checked, even for (especially for) the outside users of
this code, like the nvme code.  Best to avoid future issues with buffer
overruns.  This will require reworking the get_message_types function,
unfortunately.

You have one trace function on a bad receive message check, but lots of
other bad receive message checks with no trace.  Just a suggestion, but
it might be nice for tracking down issues to trace all the reasons a
message is dropped.

Thanks,

-corey

> 
>   [1]: https://lore.kernel.org/qemu-devel/20220520170128.4436-1-Jonathan.Cameron@huawei.com/
> 
> Signed-off-by: Klaus Jensen <k.jensen@samsung.com>
> ---
>  MAINTAINERS                   |   7 +
>  hw/arm/Kconfig                |   1 +
>  hw/i2c/Kconfig                |   4 +
>  hw/i2c/mctp.c                 | 352 ++++++++++++++++++++++++++++++++++
>  hw/i2c/meson.build            |   1 +
>  hw/i2c/smbus_master.c         |  28 +++
>  hw/i2c/trace-events           |  12 ++
>  include/hw/i2c/mctp.h         | 114 +++++++++++
>  include/hw/i2c/smbus_master.h |   3 +
>  include/net/mctp.h            |  43 +++++
>  10 files changed, 565 insertions(+)
>  create mode 100644 hw/i2c/mctp.c
>  create mode 100644 include/hw/i2c/mctp.h
>  create mode 100644 include/net/mctp.h
> 
> diff --git a/MAINTAINERS b/MAINTAINERS
> index 24154f5721c7..054aad1f3e97 100644
> --- a/MAINTAINERS
> +++ b/MAINTAINERS
> @@ -3339,6 +3339,13 @@ F: tests/qtest/adm1272-test.c
>  F: tests/qtest/max34451-test.c
>  F: tests/qtest/isl_pmbus_vr-test.c
>  
> +MCTP I2C Transport
> +M: Klaus Jensen <k.jensen@samsung.com>
> +S: Maintained
> +F: hw/i2c/mctp.c
> +F: include/hw/i2c/mctp.h
> +F: include/net/mctp.h
> +
>  Firmware schema specifications
>  M: Philippe Mathieu-Daudé <philmd@linaro.org>
>  R: Daniel P. Berrange <berrange@redhat.com>
> diff --git a/hw/arm/Kconfig b/hw/arm/Kconfig
> index b53bd7f0b2a0..d7ecbc99e5ee 100644
> --- a/hw/arm/Kconfig
> +++ b/hw/arm/Kconfig
> @@ -457,6 +457,7 @@ config ASPEED_SOC
>      select DS1338
>      select FTGMAC100
>      select I2C
> +    select MCTP_I2C
>      select DPS310
>      select PCA9552
>      select SERIAL
> diff --git a/hw/i2c/Kconfig b/hw/i2c/Kconfig
> index 14886b35dac2..3415e8421ab1 100644
> --- a/hw/i2c/Kconfig
> +++ b/hw/i2c/Kconfig
> @@ -45,3 +45,7 @@ config PCA954X
>  config PMBUS
>      bool
>      select SMBUS
> +
> +config MCTP_I2C
> +    bool
> +    select I2C
> diff --git a/hw/i2c/mctp.c b/hw/i2c/mctp.c
> new file mode 100644
> index 000000000000..0f4045d0d685
> --- /dev/null
> +++ b/hw/i2c/mctp.c
> @@ -0,0 +1,352 @@
> +/*
> + * SPDX-License-Identifier: GPL-2.0-or-later
> + *
> + * SPDX-FileCopyrightText: Copyright (c) 2022 Samsung Electronics Co., Ltd.
> + * SPDX-FileContributor: Klaus Jensen <k.jensen@samsung.com>
> + */
> +
> +#include "qemu/osdep.h"
> +#include "qemu/main-loop.h"
> +
> +#include "hw/qdev-properties.h"
> +#include "hw/i2c/i2c.h"
> +#include "hw/i2c/smbus_master.h"
> +#include "hw/i2c/mctp.h"
> +
> +#include "trace.h"
> +
> +void i2c_mctp_schedule_send(MCTPI2CEndpoint *mctp)
> +{
> +    I2CBus *i2c = I2C_BUS(qdev_get_parent_bus(DEVICE(mctp)));
> +
> +    mctp->tx.state = I2C_MCTP_STATE_TX_START_SEND;
> +
> +    i2c_bus_master(i2c, mctp->tx.bh);
> +}
> +
> +static void i2c_mctp_tx(void *opaque)
> +{
> +    DeviceState *dev = DEVICE(opaque);
> +    I2CBus *i2c = I2C_BUS(qdev_get_parent_bus(dev));
> +    I2CSlave *slave = I2C_SLAVE(dev);
> +    MCTPI2CEndpoint *mctp = MCTP_I2C_ENDPOINT(dev);
> +    MCTPI2CEndpointClass *mc = MCTP_I2C_ENDPOINT_GET_CLASS(mctp);
> +    MCTPI2CPacket *pkt = (MCTPI2CPacket *)mctp->buffer;
> +    uint8_t flags = 0;
> +
> +    switch (mctp->tx.state) {
> +    case I2C_MCTP_STATE_TX_SEND_BYTE:
> +        if (mctp->pos < mctp->len) {
> +            uint8_t byte = mctp->buffer[mctp->pos];
> +
> +            trace_i2c_mctp_tx_send_byte(mctp->pos, byte);
> +
> +            /* send next byte */
> +            i2c_send_async(i2c, byte);
> +
> +            mctp->pos++;
> +
> +            break;
> +        }
> +
> +        /* packet sent */
> +        i2c_end_transfer(i2c);
> +
> +        /* end of any control data */
> +        mctp->len = 0;
> +
> +        /* fall through */
> +
> +    case I2C_MCTP_STATE_TX_START_SEND:
> +        if (mctp->tx.is_control) {
> +            /* packet payload is already in buffer */
> +            flags |= MCTP_H_FLAGS_SOM | MCTP_H_FLAGS_EOM;
> +        } else {
> +            /* get message bytes from derived device */
> +            mctp->len = mc->get_message_bytes(mctp, pkt->mctp.payload,
> +                                              I2C_MCTP_MAXMTU, &flags);
> +        }
> +
> +        if (!mctp->len) {
> +            trace_i2c_mctp_tx_done();
> +
> +            /* no more packets needed; release the bus */
> +            i2c_bus_release(i2c);
> +
> +            mctp->state = I2C_MCTP_STATE_IDLE;
> +            mctp->tx.is_control = false;
> +
> +            break;
> +        }
> +
> +        mctp->state = I2C_MCTP_STATE_TX;
> +
> +        pkt->i2c = (MCTPI2CPacketHeader) {
> +            .dest = mctp->tx.addr & ~0x1,
> +            .prot = 0xf,
> +            .byte_count = 5 + mctp->len,
> +            .source = slave->address << 1 | 0x1,
> +        };
> +
> +        pkt->mctp.hdr = (MCTPPacketHeader) {
> +            .version = 0x1,
> +            .eid.dest = mctp->tx.eid,
> +            .eid.source = mctp->my_eid,
> +            .flags = flags | (mctp->tx.pktseq++ & 0x3) << 4 | mctp->tx.flags,
> +        };
> +
> +        mctp->len += sizeof(MCTPI2CPacket);
> +        assert(mctp->len < I2C_MCTP_MAX_LENGTH);
> +
> +        mctp->buffer[mctp->len] = i2c_smbus_pec(0, mctp->buffer, mctp->len);
> +        mctp->len++;
> +
> +        trace_i2c_mctp_tx_start_send(mctp->len);
> +
> +        i2c_start_send_async(i2c, pkt->i2c.dest >> 1);
> +
> +        /* already "sent" the destination slave address */
> +        mctp->pos = 1;
> +
> +        mctp->tx.state = I2C_MCTP_STATE_TX_SEND_BYTE;
> +
> +        break;
> +    }
> +}
> +
> +#define i2c_mctp_control_data(buf) \
> +    (i2c_mctp_payload(buf) + offsetof(MCTPControlMessage, data))
> +
> +static void i2c_mctp_handle_control_set_eid(MCTPI2CEndpoint *mctp, uint8_t eid)
> +{
> +    mctp->my_eid = eid;
> +
> +    uint8_t buf[] = {
> +        0x0, 0x0, eid, 0x0,
> +    };
> +
> +    memcpy(i2c_mctp_control_data(mctp->buffer), buf, sizeof(buf));
> +    mctp->len += sizeof(buf);
> +}
> +
> +static void i2c_mctp_handle_control_get_eid(MCTPI2CEndpoint *mctp)
> +{
> +    uint8_t buf[] = {
> +        0x0, mctp->my_eid, 0x0, 0x0,
> +    };
> +
> +    memcpy(i2c_mctp_control_data(mctp->buffer), buf, sizeof(buf));
> +    mctp->len += sizeof(buf);
> +}
> +
> +static void i2c_mctp_handle_control_get_version(MCTPI2CEndpoint *mctp)
> +{
> +    uint8_t buf[] = {
> +        0x0, 0x1, 0x0, 0x1, 0x3, 0x1,
> +    };
> +
> +    memcpy(i2c_mctp_control_data(mctp->buffer), buf, sizeof(buf));
> +    mctp->len += sizeof(buf);
> +}
> +
> +enum {
> +    MCTP_CONTROL_SET_EID                    = 0x01,
> +    MCTP_CONTROL_GET_EID                    = 0x02,
> +    MCTP_CONTROL_GET_VERSION                = 0x04,
> +    MCTP_CONTROL_GET_MESSAGE_TYPE_SUPPORT   = 0x05,
> +};
> +
> +static void i2c_mctp_handle_control(MCTPI2CEndpoint *mctp)
> +{
> +    MCTPI2CEndpointClass *mc = MCTP_I2C_ENDPOINT_GET_CLASS(mctp);
> +    MCTPControlMessage *msg = (MCTPControlMessage *)i2c_mctp_payload(mctp->buffer);
> +
> +    /* clear Rq/D */
> +    msg->flags &= 0x1f;
> +
> +    mctp->len = sizeof(MCTPControlMessage);
> +
> +    trace_i2c_mctp_handle_control(msg->command);
> +
> +    switch (msg->command) {
> +    case MCTP_CONTROL_SET_EID:
> +        i2c_mctp_handle_control_set_eid(mctp, msg->data[1]);
> +        break;
> +
> +    case MCTP_CONTROL_GET_EID:
> +        i2c_mctp_handle_control_get_eid(mctp);
> +        break;
> +
> +    case MCTP_CONTROL_GET_VERSION:
> +        i2c_mctp_handle_control_get_version(mctp);
> +        break;
> +
> +    case MCTP_CONTROL_GET_MESSAGE_TYPE_SUPPORT:
> +        mctp->len += mc->get_message_types(mctp, i2c_mctp_control_data(mctp->buffer),
> +                                           MCTP_BASELINE_MTU - mctp->len);
> +        break;
> +
> +    default:
> +        trace_i2c_mctp_unhandled_control(msg->command);
> +
> +        msg->data[0] = MCTP_CONTROL_ERROR_UNSUPPORTED_CMD;
> +        mctp->len++;
> +
> +        break;
> +    }
> +
> +    assert(mctp->len <= MCTP_BASELINE_MTU);
> +
> +    i2c_mctp_schedule_send(mctp);
> +}
> +
> +static int i2c_mctp_event_cb(I2CSlave *i2c, enum i2c_event event)
> +{
> +    MCTPI2CEndpoint *mctp = MCTP_I2C_ENDPOINT(i2c);
> +    MCTPI2CEndpointClass *mc = MCTP_I2C_ENDPOINT_GET_CLASS(mctp);
> +    MCTPI2CPacket *pkt = (MCTPI2CPacket *)mctp->buffer;
> +    size_t payload_len;
> +    uint8_t pec;
> +
> +    switch (event) {
> +    case I2C_START_SEND:
> +        if (mctp->state == I2C_MCTP_STATE_IDLE) {
> +            mctp->state = I2C_MCTP_STATE_RX_STARTED;
> +        } else if (mctp->state != I2C_MCTP_STATE_RX) {
> +            return -1;
> +        }
> +
> +        /* the i2c core eats the slave address, so put it back in */
> +        pkt->i2c.dest = i2c->address << 1;
> +        mctp->len = 1;
> +
> +        return 0;
> +
> +    case I2C_FINISH:
> +        if (mctp->len < sizeof(MCTPI2CPacket) + 1) {
> +            trace_i2c_mctp_drop("short packet");
> +            goto drop;
> +        }
> +
> +        payload_len = mctp->len - (1 + offsetof(MCTPI2CPacket, mctp.payload));
> +
> +        if (pkt->i2c.byte_count + 3 != mctp->len - 1) {
> +            trace_i2c_mctp_drop_invalid_length(pkt->i2c.byte_count + 3,
> +                                               mctp->len - 1);
> +            goto drop;
> +        }
> +
> +        pec = i2c_smbus_pec(0, mctp->buffer, mctp->len - 1);
> +        if (mctp->buffer[mctp->len - 1] != pec) {
> +            trace_i2c_mctp_drop_invalid_pec(mctp->buffer[mctp->len - 1], pec);
> +            goto drop;
> +        }
> +
> +        if (pkt->mctp.hdr.eid.dest != mctp->my_eid) {
> +            trace_i2c_mctp_drop_invalid_eid(pkt->mctp.hdr.eid.dest,
> +                                            mctp->my_eid);
> +            goto drop;
> +        }
> +
> +        if (pkt->mctp.hdr.flags & MCTP_H_FLAGS_SOM) {
> +            mctp->tx.is_control = false;
> +
> +            if (mctp->state == I2C_MCTP_STATE_RX) {
> +                mc->reset_message(mctp);
> +            }
> +
> +            mctp->state = I2C_MCTP_STATE_RX;
> +
> +            mctp->tx.addr = pkt->i2c.source;
> +            mctp->tx.eid = pkt->mctp.hdr.eid.source;
> +            mctp->tx.flags = pkt->mctp.hdr.flags & 0x7;
> +            mctp->tx.pktseq = (pkt->mctp.hdr.flags >> 4) & 0x3;
> +
> +            if ((pkt->mctp.payload[0] & 0x7f) == MCTP_MESSAGE_TYPE_CONTROL) {
> +                mctp->tx.is_control = true;
> +
> +                i2c_mctp_handle_control(mctp);
> +
> +                return 0;
> +            }
> +        } else if (mctp->state == I2C_MCTP_STATE_RX_STARTED) {
> +            trace_i2c_mctp_drop("expected SOM");
> +            goto drop;
> +        } else if (((pkt->mctp.hdr.flags >> 4) & 0x3) != (++mctp->tx.pktseq & 0x3)) {
> +            trace_i2c_mctp_drop_invalid_pktseq((pkt->mctp.hdr.flags >> 4) & 0x3,
> +                                               mctp->tx.pktseq & 0x3);
> +            goto drop;
> +        }
> +
> +        mc->put_message_bytes(mctp, i2c_mctp_payload(mctp->buffer), payload_len);
> +
> +        if (pkt->mctp.hdr.flags & MCTP_H_FLAGS_EOM) {
> +            mc->handle_message(mctp);
> +            mctp->state = I2C_MCTP_STATE_WAIT_TX;
> +        }
> +
> +        return 0;
> +
> +    default:
> +        return -1;
> +    }
> +
> +drop:
> +    mc->reset_message(mctp);
> +
> +    mctp->state = I2C_MCTP_STATE_IDLE;
> +
> +    return 0;
> +}
> +
> +static int i2c_mctp_send_cb(I2CSlave *i2c, uint8_t data)
> +{
> +    MCTPI2CEndpoint *mctp = MCTP_I2C_ENDPOINT(i2c);
> +
> +    if (mctp->len < I2C_MCTP_MAX_LENGTH) {
> +        mctp->buffer[mctp->len++] = data;
> +        return 0;
> +    }
> +
> +    return -1;
> +}
> +
> +static void i2c_mctp_instance_init(Object *obj)
> +{
> +    MCTPI2CEndpoint *mctp = MCTP_I2C_ENDPOINT(obj);
> +
> +    mctp->tx.bh = qemu_bh_new(i2c_mctp_tx, mctp);
> +}
> +
> +static Property mctp_i2c_props[] = {
> +    DEFINE_PROP_UINT8("eid", MCTPI2CEndpoint, my_eid, 0x9),
> +    DEFINE_PROP_END_OF_LIST(),
> +};
> +
> +static void i2c_mctp_class_init(ObjectClass *oc, void *data)
> +{
> +    DeviceClass *dc = DEVICE_CLASS(oc);
> +    I2CSlaveClass *k = I2C_SLAVE_CLASS(oc);
> +
> +    k->event = i2c_mctp_event_cb;
> +    k->send = i2c_mctp_send_cb;
> +
> +    device_class_set_props(dc, mctp_i2c_props);
> +}
> +
> +static const TypeInfo i2c_mctp_info = {
> +    .name = TYPE_MCTP_I2C_ENDPOINT,
> +    .parent = TYPE_I2C_SLAVE,
> +    .abstract = true,
> +    .instance_init = i2c_mctp_instance_init,
> +    .instance_size = sizeof(MCTPI2CEndpoint),
> +    .class_init = i2c_mctp_class_init,
> +    .class_size = sizeof(MCTPI2CEndpointClass),
> +};
> +
> +static void register_types(void)
> +{
> +    type_register_static(&i2c_mctp_info);
> +}
> +
> +type_init(register_types)
> diff --git a/hw/i2c/meson.build b/hw/i2c/meson.build
> index 3996564c25c6..fd1f9022fd96 100644
> --- a/hw/i2c/meson.build
> +++ b/hw/i2c/meson.build
> @@ -1,5 +1,6 @@
>  i2c_ss = ss.source_set()
>  i2c_ss.add(when: 'CONFIG_I2C', if_true: files('core.c'))
> +i2c_ss.add(when: 'CONFIG_MCTP_I2C', if_true: files('mctp.c'))
>  i2c_ss.add(when: 'CONFIG_SMBUS', if_true: files('smbus_slave.c', 'smbus_master.c'))
>  i2c_ss.add(when: 'CONFIG_ACPI_SMBUS', if_true: files('pm_smbus.c'))
>  i2c_ss.add(when: 'CONFIG_ACPI_ICH9', if_true: files('smbus_ich9.c'))
> diff --git a/hw/i2c/smbus_master.c b/hw/i2c/smbus_master.c
> index 6a53c34e70b7..47f9eb24e033 100644
> --- a/hw/i2c/smbus_master.c
> +++ b/hw/i2c/smbus_master.c
> @@ -15,6 +15,34 @@
>  #include "hw/i2c/i2c.h"
>  #include "hw/i2c/smbus_master.h"
>  
> +static uint8_t crc8(uint16_t data)
> +{
> +#define POLY (0x1070U << 3)
> +    int i;
> +
> +    for (i = 0; i < 8; i++) {
> +        if (data & 0x8000) {
> +            data = data ^ POLY;
> +        }
> +
> +        data = data << 1;
> +    }
> +
> +    return (uint8_t)(data >> 8);
> +#undef POLY
> +}
> +
> +uint8_t i2c_smbus_pec(uint8_t crc, uint8_t *buf, size_t len)
> +{
> +    int i;
> +
> +    for (i = 0; i < len; i++) {
> +        crc = crc8((crc ^ buf[i]) << 8);
> +    }
> +
> +    return crc;
> +}
> +
>  /* Master device commands.  */
>  int smbus_quick_command(I2CBus *bus, uint8_t addr, int read)
>  {
> diff --git a/hw/i2c/trace-events b/hw/i2c/trace-events
> index 8e88aa24c1ac..2e3065a99873 100644
> --- a/hw/i2c/trace-events
> +++ b/hw/i2c/trace-events
> @@ -45,3 +45,15 @@ npcm7xx_smbus_recv_fifo(const char *id, uint8_t received, uint8_t expected) "%s
>  
>  pca954x_write_bytes(uint8_t value) "PCA954X write data: 0x%02x"
>  pca954x_read_data(uint8_t value) "PCA954X read data: 0x%02x"
> +
> +# mctp.c
> +i2c_mctp_tx_start_send(size_t len) "len %zu"
> +i2c_mctp_tx_send_byte(size_t pos, uint8_t byte) "pos %zu byte 0x%"PRIx8""
> +i2c_mctp_tx_done(void) "packet sent"
> +i2c_mctp_handle_control(uint8_t command) "command 0x%"PRIx8""
> +i2c_mctp_unhandled_control(uint8_t command) "command 0x%"PRIx8""
> +i2c_mctp_drop(const char *reason) "%s"
> +i2c_mctp_drop_invalid_length(unsigned byte_count, size_t expected) "byte_count %u expected %zu"
> +i2c_mctp_drop_invalid_pec(uint8_t pec, uint8_t expected) "pec 0x%"PRIx8" expected 0x%"PRIx8""
> +i2c_mctp_drop_invalid_eid(uint8_t eid, uint8_t expected) "eid 0x%"PRIx8" expected 0x%"PRIx8""
> +i2c_mctp_drop_invalid_pktseq(uint8_t pktseq, uint8_t expected) "pktseq 0x%"PRIx8" expected 0x%"PRIx8""
> diff --git a/include/hw/i2c/mctp.h b/include/hw/i2c/mctp.h
> new file mode 100644
> index 000000000000..c53ee6a3b61b
> --- /dev/null
> +++ b/include/hw/i2c/mctp.h
> @@ -0,0 +1,114 @@
> +#ifndef QEMU_I2C_MCTP_H
> +#define QEMU_I2C_MCTP_H
> +
> +#include "qom/object.h"
> +#include "hw/qdev-core.h"
> +#include "net/mctp.h"
> +
> +typedef struct MCTPI2CPacketHeader {
> +    uint8_t dest;
> +    uint8_t prot;
> +    uint8_t byte_count;
> +    uint8_t source;
> +} MCTPI2CPacketHeader;
> +
> +typedef struct MCTPI2CPacket {
> +    MCTPI2CPacketHeader i2c;
> +    MCTPPacket          mctp;
> +} MCTPI2CPacket;
> +
> +#define i2c_mctp_payload(buf) (buf + offsetof(MCTPI2CPacket, mctp.payload))
> +
> +#define TYPE_MCTP_I2C_ENDPOINT "mctp-i2c-endpoint"
> +OBJECT_DECLARE_TYPE(MCTPI2CEndpoint, MCTPI2CEndpointClass, MCTP_I2C_ENDPOINT)
> +
> +struct MCTPI2CEndpointClass {
> +    I2CSlaveClass parent_class;
> +
> +    int (*put_message_bytes)(MCTPI2CEndpoint *mctp, uint8_t *buf, size_t len);
> +    size_t (*get_message_bytes)(MCTPI2CEndpoint *mctp, uint8_t *buf,
> +                                size_t maxlen, uint8_t *mctp_flags);
> +
> +    void (*handle_message)(MCTPI2CEndpoint *mctp);
> +    void (*reset_message)(MCTPI2CEndpoint *mctp);
> +
> +    size_t (*get_message_types)(MCTPI2CEndpoint *mctp, uint8_t *data,
> +                                size_t maxlen);
> +};
> +
> +/*
> + * Maximum value of the SMBus Block Write "Byte Count" field (8 bits).
> + *
> + * This is the count of bytes that follow the Byte Count field and up to, but
> + * not including, the PEC byte.
> + */
> +#define I2C_MCTP_MAXBLOCK 255
> +
> +/*
> + * Maximum Transmission Unit under I2C.
> + *
> + * This is for the MCTP Packet Payload (255, subtracting the 4 byte MCTP Packet
> + * Header or the 1 byte MCTP/I2C piggy-backed source address).
> + */
> +#define I2C_MCTP_MAXMTU (I2C_MCTP_MAXBLOCK - (sizeof(MCTPPacketHeader) + 1))
> +
> +/*
> + * Maximum length of an MCTP/I2C packet.
> + *
> + * This is the sum of the three I2C header bytes (Destination target address,
> + * Command Code and Byte Count), the maximum number of bytes in a message (255)
> + * and the 1 byte Packet Error Code.
> + */
> +#define I2C_MCTP_MAX_LENGTH (3 + I2C_MCTP_MAXBLOCK + 1)
> +
> +/*
> + * Maximum length of an MCTP/I2C Control Message.
> + *
> + * This is the 64 byte MCTP Baseline Maximum Transmission Unit, adding the
> + * combined MCTP/I2C headers and the trailing 1 byte PEC.
> + */
> +#define I2C_MCTP_CONTROL_MAX_LENGTH \
> +    (sizeof(MCTPI2CPacket) + MCTP_BASELINE_MTU + 1)
> +
> +typedef enum {
> +    I2C_MCTP_STATE_IDLE,
> +    I2C_MCTP_STATE_RX_STARTED,
> +    I2C_MCTP_STATE_RX,
> +    I2C_MCTP_STATE_WAIT_TX,
> +    I2C_MCTP_STATE_TX,
> +} MCTPState;
> +
> +typedef enum {
> +    I2C_MCTP_STATE_TX_START_SEND,
> +    I2C_MCTP_STATE_TX_SEND_BYTE,
> +} MCTPTxState;
> +
> +typedef struct MCTPI2CEndpoint {
> +    I2CSlave parent_obj;
> +    I2CBus *i2c;
> +
> +    MCTPState state;
> +
> +    /* mctp endpoint identifier */
> +    uint8_t my_eid;
> +
> +    uint8_t  buffer[I2C_MCTP_MAX_LENGTH];
> +    uint64_t pos;
> +    size_t   len;
> +
> +    struct {
> +        MCTPTxState state;
> +        bool is_control;
> +
> +        uint8_t eid;
> +        uint8_t addr;
> +        uint8_t pktseq;
> +        uint8_t flags;
> +
> +        QEMUBH *bh;
> +    } tx;
> +} MCTPI2CEndpoint;
> +
> +void i2c_mctp_schedule_send(MCTPI2CEndpoint *mctp);
> +
> +#endif /* QEMU_I2C_MCTP_H */
> diff --git a/include/hw/i2c/smbus_master.h b/include/hw/i2c/smbus_master.h
> index bb13bc423c22..ea5eff3a2cd0 100644
> --- a/include/hw/i2c/smbus_master.h
> +++ b/include/hw/i2c/smbus_master.h
> @@ -27,6 +27,9 @@
>  
>  #include "hw/i2c/i2c.h"
>  
> +/* SMBus PEC */
> +uint8_t i2c_smbus_pec(uint8_t crc, uint8_t *buf, size_t len);
> +
>  /* Master device commands.  */
>  int smbus_quick_command(I2CBus *bus, uint8_t addr, int read);
>  int smbus_receive_byte(I2CBus *bus, uint8_t addr);
> diff --git a/include/net/mctp.h b/include/net/mctp.h
> new file mode 100644
> index 000000000000..c936224ecf60
> --- /dev/null
> +++ b/include/net/mctp.h
> @@ -0,0 +1,43 @@
> +#ifndef QEMU_MCTP_H
> +#define QEMU_MCTP_H
> +
> +#define MCTP_BASELINE_MTU 64
> +
> +enum {
> +    MCTP_H_FLAGS_EOM = 1 << 6,
> +    MCTP_H_FLAGS_SOM = 1 << 7,
> +};
> +
> +enum {
> +    MCTP_MESSAGE_TYPE_CONTROL   = 0x0,
> +    MCTP_MESSAGE_TYPE_NMI       = 0x4,
> +
> +    MCTP_MESSAGE_IC             = 1 << 7,
> +};
> +
> +typedef struct MCTPPacketHeader {
> +    uint8_t version;
> +    struct {
> +        uint8_t dest;
> +        uint8_t source;
> +    } eid;
> +    uint8_t flags;
> +} MCTPPacketHeader;
> +
> +typedef struct MCTPPacket {
> +    MCTPPacketHeader hdr;
> +    uint8_t          payload[];
> +} MCTPPacket;
> +
> +typedef struct MCTPControlMessage {
> +    uint8_t type;
> +    uint8_t flags;
> +    uint8_t command;
> +    uint8_t data[];
> +} MCTPControlMessage;
> +
> +enum {
> +    MCTP_CONTROL_ERROR_UNSUPPORTED_CMD = 0x5,
> +};
> +
> +#endif /* QEMU_MCTP_H */
> -- 
> 2.40.0
> 
>

On Apr 25 10:19, Corey Minyard wrote:
> On Tue, Apr 25, 2023 at 08:35:38AM +0200, Klaus Jensen wrote:
> > From: Klaus Jensen <k.jensen@samsung.com>
> > 
> > Add an abstract MCTP over I2C endpoint model. This implements MCTP
> > control message handling as well as handling the actual I2C transport
> > (packetization).
> > 
> > Devices are intended to derive from this and implement the class
> > methods.
> > 
> > Parts of this implementation is inspired by code[1] previously posted by
> > Jonathan Cameron.
> 
> All in all this looks good.  Two comments:
> 
> I would like to see the buffer handling consolidated into one function
> and the length checked, even for (especially for) the outside users of
> this code, like the nvme code.  Best to avoid future issues with buffer
> overruns.  This will require reworking the get_message_types function,
> unfortunately.
> 

Right now the implementations (i.e. hw/nvme/nmi-i2c.c) writes directly
into the mctp core buffer for get_message_bytes(). The contract is that
it must not write more than the `maxlen` parameter. Is that bad? Would
it be better that get_message_bytes() returned a pointer to its own
buffer that hw/mctp can then copy from?

> You have one trace function on a bad receive message check, but lots of
> other bad receive message checks with no trace.  Just a suggestion, but
> it might be nice for tracking down issues to trace all the reasons a
> message is dropped.
> 

Sounds reasonable! :)

Thanks for the review!

On Wed, Apr 26, 2023 at 09:11:16AM +0200, Klaus Jensen wrote:
> On Apr 25 10:19, Corey Minyard wrote:
> > On Tue, Apr 25, 2023 at 08:35:38AM +0200, Klaus Jensen wrote:
> > > From: Klaus Jensen <k.jensen@samsung.com>
> > > 
> > > Add an abstract MCTP over I2C endpoint model. This implements MCTP
> > > control message handling as well as handling the actual I2C transport
> > > (packetization).
> > > 
> > > Devices are intended to derive from this and implement the class
> > > methods.
> > > 
> > > Parts of this implementation is inspired by code[1] previously posted by
> > > Jonathan Cameron.
> > 
> > All in all this looks good.  Two comments:
> > 
> > I would like to see the buffer handling consolidated into one function
> > and the length checked, even for (especially for) the outside users of
> > this code, like the nvme code.  Best to avoid future issues with buffer
> > overruns.  This will require reworking the get_message_types function,
> > unfortunately.
> > 
> 
> Right now the implementations (i.e. hw/nvme/nmi-i2c.c) writes directly
> into the mctp core buffer for get_message_bytes(). The contract is that
> it must not write more than the `maxlen` parameter. Is that bad? Would
> it be better that get_message_bytes() returned a pointer to its own
> buffer that hw/mctp can then copy from?

qemu has had several instances of unchecked writing into a buffer
eventually getting it into trouble.  It might be ok in the beginning,
but as things change and code is added, something might come in that is
not ok.

nmi_get_message_types(), for instance, does not check maxlen.

It may be borderline paranoia, but I've seen too many instances where
paranoia was warranted :).

Plus I think it would make the code a little cleaner and easier to
maintain.  If you wanted to change how the buffer worked, trace data put
into the buffer, or something like that, all the code to handle that is
in one place.

> 
> > You have one trace function on a bad receive message check, but lots of
> > other bad receive message checks with no trace.  Just a suggestion, but
> > it might be nice for tracking down issues to trace all the reasons a
> > message is dropped.
> > 
> 
> Sounds reasonable! :)
> 
> Thanks for the review!

Thank you for the submission :).

-corey

On May 25 12:27, Jonathan Cameron wrote:
> On Tue, 25 Apr 2023 08:35:38 +0200
> Klaus Jensen <its@irrelevant.dk> wrote:
> 
> > From: Klaus Jensen <k.jensen@samsung.com>
> > 
> > Add an abstract MCTP over I2C endpoint model. This implements MCTP
> > control message handling as well as handling the actual I2C transport
> > (packetization).
> > 
> > Devices are intended to derive from this and implement the class
> > methods.
> > 
> > Parts of this implementation is inspired by code[1] previously posted by
> > Jonathan Cameron.
> > 
> >   [1]: https://lore.kernel.org/qemu-devel/20220520170128.4436-1-Jonathan.Cameron@huawei.com/
> > 
> > Signed-off-by: Klaus Jensen <k.jensen@samsung.com>
> 
> This is very useful for the CXL MCTP CCI support - got rid of most of the
> nasty code when I moved over to using this (will post code shortly)
> 
> A few comments inline - but all trivial stuff.
> 
> What I can give now though is:
> Tested-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
> 

Hi Jonathan,

This came at just the right time! I was finally preparing v3 since Lior
is also requesting that this gets merged sooner rather than later ;)

I'll work in your very resonable comments (thanks!) and ship it.


Thanks again,
Klaus