From patchwork Fri Dec 30 12:11:57 2022 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Patchwork-Submitter: David Woodhouse X-Patchwork-Id: 1720398 Return-Path: X-Original-To: incoming@patchwork.ozlabs.org Delivered-To: patchwork-incoming@legolas.ozlabs.org Authentication-Results: legolas.ozlabs.org; spf=pass (sender SPF authorized) smtp.mailfrom=nongnu.org (client-ip=209.51.188.17; helo=lists.gnu.org; envelope-from=qemu-devel-bounces+incoming=patchwork.ozlabs.org@nongnu.org; receiver=) Authentication-Results: legolas.ozlabs.org; dkim=fail reason="signature verification failed" (2048-bit key; secure) header.d=infradead.org header.i=@infradead.org header.a=rsa-sha256 header.s=casper.20170209 header.b=j94Be64t; dkim-atps=neutral Received: from lists.gnu.org (lists.gnu.org [209.51.188.17]) (using TLSv1.2 with cipher ECDHE-ECDSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by legolas.ozlabs.org (Postfix) with ESMTPS id 4Nk4M7375Zz23dV for ; Fri, 30 Dec 2022 23:29:23 +1100 (AEDT) Received: from localhost ([::1] helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1pBEHE-0001LS-M4; Fri, 30 Dec 2022 07:14:21 -0500 Received: from eggs.gnu.org ([2001:470:142:3::10]) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1pBEFx-0007uP-MI for qemu-devel@nongnu.org; Fri, 30 Dec 2022 07:13:01 -0500 Received: from casper.infradead.org ([2001:8b0:10b:1236::1]) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1pBEFr-00050h-0j for qemu-devel@nongnu.org; Fri, 30 Dec 2022 07:13:01 -0500 DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=casper.20170209; h=Sender:Content-Transfer-Encoding: Content-Type:MIME-Version:References:In-Reply-To:Message-Id:Date:Subject:Cc: To:From:Reply-To:Content-ID:Content-Description; bh=8H7pJXSOgN+szwAWkuBMvHFY7wLSar+M/8ySBTFzn5g=; b=j94Be64tzWYXUYzhShNfSiSe9T iNMc+AsfZ2mWbpbr17iJEDUqFlpYXojIN+S9unGCx+1rUyqskzb5E+9oDiRcWwVgCPHGuCg+NLhGg tgx9ZU5X7UWaFLIfRC/IJbc33+EcYr+v44txO3+u2dtYR2i6YG2wzP4dcK/o8MOPt3fv8j1MVkpXy I7I0bD7DdaIJ/+icmYZuAgwEBdiObV++TuebJNo42hfz31NRIBFWQwrsMbWzwX2AKEGv5siYm5Xxm fkaRL4BmOuE9sVstbI1VrunbXnovdP0KU5WSEoAQJ4G8dC7gOGqAwP3Ke2Lb5F68XmohQuPTxop/b 0Bb+WOvA==; Received: from i7.infradead.org ([2001:8b0:10b:1:21e:67ff:fecb:7a92]) by casper.infradead.org with esmtpsa (Exim 4.94.2 #2 (Red Hat Linux)) id 1pBEFk-00Ac81-Oi; Fri, 30 Dec 2022 12:12:48 +0000 Received: from dwoodhou by i7.infradead.org with local (Exim 4.94.2 #2 (Red Hat Linux)) id 1pBEFZ-005Nw4-FQ; Fri, 30 Dec 2022 12:12:37 +0000 From: David Woodhouse To: qemu-devel@nongnu.org Cc: Paolo Bonzini , Paul Durrant , Joao Martins , Ankur Arora , =?utf-8?q?Philippe_Mathieu-Daud?= =?utf-8?q?=C3=A9?= , Thomas Huth , =?utf-8?q?Alex_Benn=C3=A9e?= , Juan Quintela , "Dr . David Alan Gilbert" , Claudio Fontana , Julien Grall Subject: [RFC PATCH v5 14/52] hw/xen: Add xen_overlay device for emulating shared xenheap pages Date: Fri, 30 Dec 2022 12:11:57 +0000 Message-Id: <20221230121235.1282915-15-dwmw2@infradead.org> X-Mailer: git-send-email 2.35.3 In-Reply-To: <20221230121235.1282915-1-dwmw2@infradead.org> References: <20221230121235.1282915-1-dwmw2@infradead.org> MIME-Version: 1.0 X-SRS-Rewrite: SMTP reverse-path rewritten from by casper.infradead.org. See http://www.infradead.org/rpr.html Received-SPF: none client-ip=2001:8b0:10b:1236::1; envelope-from=BATV+1132f1bfe572585e6c7f+7068+infradead.org+dwmw2@casper.srs.infradead.org; helo=casper.infradead.org X-Spam_score_int: -43 X-Spam_score: -4.4 X-Spam_bar: ---- X-Spam_report: (-4.4 / 5.0 requ) BAYES_00=-1.9, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_MED=-2.3, SPF_HELO_NONE=0.001, SPF_NONE=0.001 autolearn=ham autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: qemu-devel-bounces+incoming=patchwork.ozlabs.org@nongnu.org Sender: qemu-devel-bounces+incoming=patchwork.ozlabs.org@nongnu.org From: David Woodhouse For the shared info page and for grant tables, Xen shares its own pages from the "Xen heap" to the guest. The guest requests that a given page from a certain address space (XENMAPSPACE_shared_info, etc.) be mapped to a given GPA using the XENMEM_add_to_physmap hypercall. To support that in qemu when *emulating* Xen, create a memory region (migratable) and allow it to be mapped as an overlay when requested. Xen theoretically allows the same page to be mapped multiple times into the guest, but that's hard to track and reinstate over migration, so we automatically *unmap* any previous mapping when creating a new one. This approach has been used in production with.... a non-trivial number of guests expecting true Xen, without any problems yet being noticed. This adds just the shared info page for now. The grant tables will be a larger region, and will need to be overlaid one page at a time. I think that means I need to create separate aliases for each page of the overall grant_frames region, so that they can be mapped individually. Signed-off-by: David Woodhouse --- hw/i386/kvm/meson.build | 1 + hw/i386/kvm/xen_overlay.c | 200 ++++++++++++++++++++++++++++++++++++++ hw/i386/kvm/xen_overlay.h | 20 ++++ include/sysemu/kvm_xen.h | 4 + 4 files changed, 225 insertions(+) create mode 100644 hw/i386/kvm/xen_overlay.c create mode 100644 hw/i386/kvm/xen_overlay.h diff --git a/hw/i386/kvm/meson.build b/hw/i386/kvm/meson.build index 95467f1ded..6165cbf019 100644 --- a/hw/i386/kvm/meson.build +++ b/hw/i386/kvm/meson.build @@ -4,5 +4,6 @@ i386_kvm_ss.add(when: 'CONFIG_APIC', if_true: files('apic.c')) i386_kvm_ss.add(when: 'CONFIG_I8254', if_true: files('i8254.c')) i386_kvm_ss.add(when: 'CONFIG_I8259', if_true: files('i8259.c')) i386_kvm_ss.add(when: 'CONFIG_IOAPIC', if_true: files('ioapic.c')) +i386_kvm_ss.add(when: 'CONFIG_XEN_EMU', if_true: files('xen_overlay.c')) i386_ss.add_all(when: 'CONFIG_KVM', if_true: i386_kvm_ss) diff --git a/hw/i386/kvm/xen_overlay.c b/hw/i386/kvm/xen_overlay.c new file mode 100644 index 0000000000..331dea6b8b --- /dev/null +++ b/hw/i386/kvm/xen_overlay.c @@ -0,0 +1,200 @@ +/* + * QEMU Xen emulation: Shared/overlay pages support + * + * Copyright © 2022 Amazon.com, Inc. or its affiliates. All Rights Reserved. + * + * Authors: David Woodhouse + * + * This work is licensed under the terms of the GNU GPL, version 2 or later. + * See the COPYING file in the top-level directory. + */ + +#include "qemu/osdep.h" +#include "qemu/host-utils.h" +#include "qemu/module.h" +#include "qemu/main-loop.h" +#include "qapi/error.h" +#include "qom/object.h" +#include "exec/target_page.h" +#include "exec/address-spaces.h" +#include "migration/vmstate.h" + +#include "hw/sysbus.h" +#include "hw/xen/xen.h" +#include "xen_overlay.h" + +#include "sysemu/kvm.h" +#include "sysemu/kvm_xen.h" +#include + +#include "standard-headers/xen/memory.h" + + +#define TYPE_XEN_OVERLAY "xen-overlay" +OBJECT_DECLARE_SIMPLE_TYPE(XenOverlayState, XEN_OVERLAY) + +#define XEN_PAGE_SHIFT 12 +#define XEN_PAGE_SIZE (1ULL << XEN_PAGE_SHIFT) + +struct XenOverlayState { + /*< private >*/ + SysBusDevice busdev; + /*< public >*/ + + MemoryRegion shinfo_mem; + void *shinfo_ptr; + uint64_t shinfo_gpa; +}; + +struct XenOverlayState *xen_overlay_singleton; + +static void xen_overlay_map_page_locked(MemoryRegion *page, uint64_t gpa) +{ + /* + * Xen allows guests to map the same page as many times as it likes + * into guest physical frames. We don't, because it would be hard + * to track and restore them all. One mapping of each page is + * perfectly sufficient for all known guests... and we've tested + * that theory on a few now in other implementations. dwmw2. + */ + if (memory_region_is_mapped(page)) { + if (gpa == INVALID_GPA) { + memory_region_del_subregion(get_system_memory(), page); + } else { + /* Just move it */ + memory_region_set_address(page, gpa); + } + } else if (gpa != INVALID_GPA) { + memory_region_add_subregion_overlap(get_system_memory(), gpa, page, 0); + } +} + +/* KVM is the only existing back end for now. Let's not overengineer it yet. */ +static int xen_overlay_set_be_shinfo(uint64_t gfn) +{ + struct kvm_xen_hvm_attr xa = { + .type = KVM_XEN_ATTR_TYPE_SHARED_INFO, + .u.shared_info.gfn = gfn, + }; + + return kvm_vm_ioctl(kvm_state, KVM_XEN_HVM_SET_ATTR, &xa); +} + + +static void xen_overlay_realize(DeviceState *dev, Error **errp) +{ + XenOverlayState *s = XEN_OVERLAY(dev); + + if (xen_mode != XEN_EMULATE) { + error_setg(errp, "Xen overlay page support is for Xen emulation"); + return; + } + + memory_region_init_ram(&s->shinfo_mem, OBJECT(dev), "xen:shared_info", + XEN_PAGE_SIZE, &error_abort); + memory_region_set_enabled(&s->shinfo_mem, true); + + s->shinfo_ptr = memory_region_get_ram_ptr(&s->shinfo_mem); + s->shinfo_gpa = INVALID_GPA; + memset(s->shinfo_ptr, 0, XEN_PAGE_SIZE); +} + +static int xen_overlay_post_load(void *opaque, int version_id) +{ + XenOverlayState *s = opaque; + + if (s->shinfo_gpa != INVALID_GPA) { + xen_overlay_map_page_locked(&s->shinfo_mem, s->shinfo_gpa); + xen_overlay_set_be_shinfo(s->shinfo_gpa >> XEN_PAGE_SHIFT); + } + + return 0; +} + +static bool xen_overlay_is_needed(void *opaque) +{ + return xen_mode == XEN_EMULATE; +} + +static const VMStateDescription xen_overlay_vmstate = { + .name = "xen_overlay", + .version_id = 1, + .minimum_version_id = 1, + .needed = xen_overlay_is_needed, + .post_load = xen_overlay_post_load, + .fields = (VMStateField[]) { + VMSTATE_UINT64(shinfo_gpa, XenOverlayState), + VMSTATE_END_OF_LIST() + } +}; + +static void xen_overlay_class_init(ObjectClass *klass, void *data) +{ + DeviceClass *dc = DEVICE_CLASS(klass); + + dc->realize = xen_overlay_realize; + dc->vmsd = &xen_overlay_vmstate; +} + +static const TypeInfo xen_overlay_info = { + .name = TYPE_XEN_OVERLAY, + .parent = TYPE_SYS_BUS_DEVICE, + .instance_size = sizeof(XenOverlayState), + .class_init = xen_overlay_class_init, +}; + +void xen_overlay_create(void) +{ + xen_overlay_singleton = XEN_OVERLAY(sysbus_create_simple(TYPE_XEN_OVERLAY, + -1, NULL)); +} + +static void xen_overlay_register_types(void) +{ + type_register_static(&xen_overlay_info); +} + +type_init(xen_overlay_register_types) + +int xen_overlay_map_shinfo_page(uint64_t gpa) +{ + XenOverlayState *s = xen_overlay_singleton; + int ret; + + if (!s) { + return -ENOENT; + } + + qemu_mutex_lock_iothread(); + if (s->shinfo_gpa) { + /* If removing shinfo page, turn the kernel magic off first */ + ret = xen_overlay_set_be_shinfo(INVALID_GFN); + if (ret) { + goto out; + } + } + + xen_overlay_map_page_locked(&s->shinfo_mem, gpa); + if (gpa != INVALID_GPA) { + ret = xen_overlay_set_be_shinfo(gpa >> XEN_PAGE_SHIFT); + if (ret) { + goto out; + } + } + s->shinfo_gpa = gpa; + out: + qemu_mutex_unlock_iothread(); + + return ret; +} + +void *xen_overlay_get_shinfo_ptr(void) +{ + XenOverlayState *s = xen_overlay_singleton; + + if (!s) { + return NULL; + } + + return s->shinfo_ptr; +} diff --git a/hw/i386/kvm/xen_overlay.h b/hw/i386/kvm/xen_overlay.h new file mode 100644 index 0000000000..00cff05bb0 --- /dev/null +++ b/hw/i386/kvm/xen_overlay.h @@ -0,0 +1,20 @@ +/* + * QEMU Xen emulation: Shared/overlay pages support + * + * Copyright © 2022 Amazon.com, Inc. or its affiliates. All Rights Reserved. + * + * Authors: David Woodhouse + * + * This work is licensed under the terms of the GNU GPL, version 2 or later. + * See the COPYING file in the top-level directory. + */ + +#ifndef QEMU_XEN_OVERLAY_H +#define QEMU_XEN_OVERLAY_H + +void xen_overlay_create(void); + +int xen_overlay_map_shinfo_page(uint64_t gpa); +void *xen_overlay_get_shinfo_ptr(void); + +#endif /* QEMU_XEN_OVERLAY_H */ diff --git a/include/sysemu/kvm_xen.h b/include/sysemu/kvm_xen.h index 296533f2d5..3e43cd7843 100644 --- a/include/sysemu/kvm_xen.h +++ b/include/sysemu/kvm_xen.h @@ -12,6 +12,10 @@ #ifndef QEMU_SYSEMU_KVM_XEN_H #define QEMU_SYSEMU_KVM_XEN_H +/* The KVM API uses these to indicate "no GPA" or "no GFN" */ +#define INVALID_GPA UINT64_MAX +#define INVALID_GFN UINT64_MAX + uint32_t kvm_xen_get_caps(void); #define kvm_xen_has_cap(cap) (!!(kvm_xen_get_caps() & \