From patchwork Fri Oct 25 10:41:03 2024 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: David Hildenbrand X-Patchwork-Id: 13850485 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from lists.gnu.org (lists.gnu.org [209.51.188.17]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 209BAD0C5FD for ; Fri, 25 Oct 2024 10:42:21 +0000 (UTC) Received: from localhost ([::1] helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1t4Hkv-0003pK-VC; Fri, 25 Oct 2024 06:41:22 -0400 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 1t4Hkt-0003on-C8 for qemu-devel@nongnu.org; Fri, 25 Oct 2024 06:41:19 -0400 Received: from us-smtp-delivery-124.mimecast.com ([170.10.129.124]) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1t4Hkr-00032e-3O for qemu-devel@nongnu.org; Fri, 25 Oct 2024 06:41:19 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1729852874; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version: content-transfer-encoding:content-transfer-encoding; bh=ylTp1QLVbhe6U4eqZf0jmNJnLxdYGk1Ss/G/3MPthlA=; b=gjAMn5EB5btpurgcLJ1BmUbUmrb9lupElh0QRmkNCOHoHhZmj4MK+Nc2YrzalprItl35z3 9Vt0j6CssuHh65hr55OO/S7K61C2QLUgqEcCr18TwzM0EAKu5sIM/9FmZL5Ma1bUddo/pM JzZ/VImIIbFcTzqd9un4tku0CPTXSCY= Received: from mx-prod-mc-04.mail-002.prod.us-west-2.aws.redhat.com (ec2-54-186-198-63.us-west-2.compute.amazonaws.com [54.186.198.63]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_256_GCM_SHA384) id us-mta-619-l6QxU85rM2qcAnhblcCa5g-1; Fri, 25 Oct 2024 06:41:11 -0400 X-MC-Unique: l6QxU85rM2qcAnhblcCa5g-1 Received: from mx-prod-int-05.mail-002.prod.us-west-2.aws.redhat.com (mx-prod-int-05.mail-002.prod.us-west-2.aws.redhat.com [10.30.177.17]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits) server-digest SHA256) (No client certificate requested) by mx-prod-mc-04.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id 2BF7F1945114; Fri, 25 Oct 2024 10:41:07 +0000 (UTC) Received: from t14s.fritz.box (unknown [10.22.80.53]) by mx-prod-int-05.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTP id 9367A1955F43; Fri, 25 Oct 2024 10:41:04 +0000 (UTC) From: David Hildenbrand To: qemu-devel@nongnu.org Cc: David Hildenbrand , "Michael S. Tsirkin" , Juraj Marcin , Peter Maydell Subject: [PATCH v1] virtio-mem: unplug memory only during system resets, not device resets Date: Fri, 25 Oct 2024 12:41:03 +0200 Message-ID: <20241025104103.342188-1-david@redhat.com> MIME-Version: 1.0 X-Scanned-By: MIMEDefang 3.0 on 10.30.177.17 Received-SPF: pass client-ip=170.10.129.124; envelope-from=david@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: -40 X-Spam_score: -4.1 X-Spam_bar: ---- X-Spam_report: (-4.1 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.263, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_NONE=-0.0001, RCVD_IN_MSPIKE_H2=-1.697, RCVD_IN_VALIDITY_CERTIFIED_BLOCKED=0.001, RCVD_IN_VALIDITY_RPBL_BLOCKED=0.001, SPF_HELO_NONE=0.001, SPF_PASS=-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+qemu-devel=archiver.kernel.org@nongnu.org Sender: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org We recently converted from the LegacyReset to the new reset framework in commit c009a311e939 ("virtio-mem: Use new Resettable framework instead of LegacyReset") to be able to use the ResetType to filter out wakeup resets. However, this change had an undesired implications: as we override the Resettable interface methods in VirtIOMEMClass, the reset handler will not only get called during system resets (i.e., qemu_devices_reset()) but also during any direct or indirect device rests (e.g., device_cold_reset()). Further, we might now receive two reset callbacks during qemu_devices_reset(), first when reset by a parent and later when reset directly. The memory state of virtio-mem devices is rather special: it's supposed to be persistent/unchanged during most resets (similar to resetting a hard disk will not destroy the data), unless actually cold-resetting the whole system (different to a hard disk where a reboot will not destroy the data): ripping out system RAM is something guest OSes don't particularly enjoy, but we want to detect when rebooting to an OS that does not support virtio-mem and wouldn't be able to detect+use the memory -- and we want to force-defragment hotplugged memory to also shrink the usable device memory region. So we rally want to catch system resets to do that. On supported targets (e.g., x86), getting a cold reset on the device/parent triggers is not that easy (but looks like PCI code might trigger it), so this implication went unnoticed. However, with upcoming s390x support it is problematic: during kdump, s390x triggers a subsystem reset, ending up in s390_machine_reset() and calling only subsystem_reset() instead of qemu_devices_reset() -- because it's not a full system reset. In subsystem_reset(), s390x performs a device_cold_reset() of any TYPE_VIRTUAL_CSS_BRIDGE device, which ends up resetting all children, including the virtio-mem device. Consequently, we wrongly detect a system reset and unplug all device memory, resulting in hotplugged memory not getting included in the crash dump -- undesired. We really must not mess with hotplugged memory state during simple device resets. To fix, create+register a new reset object that will only get triggered during qemu_devices_reset() calls, but not during any other resets as it is logically not the child of any other object. Cc: "Michael S. Tsirkin" Cc: Juraj Marcin Cc: Peter Maydell Signed-off-by: David Hildenbrand --- hw/virtio/virtio-mem.c | 103 +++++++++++++++++++++++---------- include/hw/virtio/virtio-mem.h | 12 +++- 2 files changed, 83 insertions(+), 32 deletions(-) diff --git a/hw/virtio/virtio-mem.c b/hw/virtio/virtio-mem.c index ae1e81d7ba..08e0e9da1c 100644 --- a/hw/virtio/virtio-mem.c +++ b/hw/virtio/virtio-mem.c @@ -956,6 +956,7 @@ static void virtio_mem_device_realize(DeviceState *dev, Error **errp) VirtIOMEM *vmem = VIRTIO_MEM(dev); uint64_t page_size; RAMBlock *rb; + Object *obj; int ret; if (!vmem->memdev) { @@ -1121,7 +1122,28 @@ static void virtio_mem_device_realize(DeviceState *dev, Error **errp) vmstate_register_any(VMSTATE_IF(vmem), &vmstate_virtio_mem_device_early, vmem); } - qemu_register_resettable(OBJECT(vmem)); + + /* + * We only want to unplug all memory to start with a clean slate when + * it is safe for the guest -- during system resets that call + * qemu_devices_reset(). + * + * We'll filter out selected qemu_devices_reset() calls used for other + * purposes, like resetting all devices during wakeup from suspend on + * x86 based on the reset type passed to qemu_devices_reset(). + * + * Unplugging all memory during simple device resets can result in the VM + * unexpectedly losing RAM, corrupting VM state. + * + * Simple device resets (or resets triggered by getting a parent device + * reset) must not change the state of plugged memory blocks. Therefore, + * we need a dedicated reset object that only gets called during + * qemu_devices_reset(). + */ + obj = object_new(TYPE_VIRTIO_MEM_SYSTEM_RESET); + vmem->system_reset = VIRTIO_MEM_SYSTEM_RESET(obj); + vmem->system_reset->vmem = vmem; + qemu_register_resettable(obj); /* * Set ourselves as RamDiscardManager before the plug handler maps the @@ -1141,7 +1163,10 @@ static void virtio_mem_device_unrealize(DeviceState *dev) * found via an address space anymore. Unset ourselves. */ memory_region_set_ram_discard_manager(&vmem->memdev->mr, NULL); - qemu_unregister_resettable(OBJECT(vmem)); + + qemu_unregister_resettable(OBJECT(vmem->system_reset)); + object_unref(OBJECT(vmem->system_reset)); + if (vmem->early_migration) { vmstate_unregister(VMSTATE_IF(vmem), &vmstate_virtio_mem_device_early, vmem); @@ -1841,38 +1866,12 @@ static void virtio_mem_unplug_request_check(VirtIOMEM *vmem, Error **errp) } } -static ResettableState *virtio_mem_get_reset_state(Object *obj) -{ - VirtIOMEM *vmem = VIRTIO_MEM(obj); - return &vmem->reset_state; -} - -static void virtio_mem_system_reset_hold(Object *obj, ResetType type) -{ - VirtIOMEM *vmem = VIRTIO_MEM(obj); - - /* - * When waking up from standby/suspend-to-ram, do not unplug any memory. - */ - if (type == RESET_TYPE_WAKEUP) { - return; - } - - /* - * During usual resets, we will unplug all memory and shrink the usable - * region size. This is, however, not possible in all scenarios. Then, - * the guest has to deal with this manually (VIRTIO_MEM_REQ_UNPLUG_ALL). - */ - virtio_mem_unplug_all(vmem); -} - static void virtio_mem_class_init(ObjectClass *klass, void *data) { DeviceClass *dc = DEVICE_CLASS(klass); VirtioDeviceClass *vdc = VIRTIO_DEVICE_CLASS(klass); VirtIOMEMClass *vmc = VIRTIO_MEM_CLASS(klass); RamDiscardManagerClass *rdmc = RAM_DISCARD_MANAGER_CLASS(klass); - ResettableClass *rc = RESETTABLE_CLASS(klass); device_class_set_props(dc, virtio_mem_properties); dc->vmsd = &vmstate_virtio_mem; @@ -1899,9 +1898,6 @@ static void virtio_mem_class_init(ObjectClass *klass, void *data) rdmc->replay_discarded = virtio_mem_rdm_replay_discarded; rdmc->register_listener = virtio_mem_rdm_register_listener; rdmc->unregister_listener = virtio_mem_rdm_unregister_listener; - - rc->get_state = virtio_mem_get_reset_state; - rc->phases.hold = virtio_mem_system_reset_hold; } static const TypeInfo virtio_mem_info = { @@ -1924,3 +1920,48 @@ static void virtio_register_types(void) } type_init(virtio_register_types) + +OBJECT_DEFINE_SIMPLE_TYPE_WITH_INTERFACES(VirtioMemSystemReset, virtio_mem_system_reset, VIRTIO_MEM_SYSTEM_RESET, OBJECT, { TYPE_RESETTABLE_INTERFACE }, { }) + +static void virtio_mem_system_reset_init(Object *obj) +{ +} + +static void virtio_mem_system_reset_finalize(Object *obj) +{ +} + +static ResettableState *virtio_mem_system_reset_get_state(Object *obj) +{ + VirtioMemSystemReset *vmem_reset = VIRTIO_MEM_SYSTEM_RESET(obj); + + return &vmem_reset->reset_state; +} + +static void virtio_mem_system_reset_hold(Object *obj, ResetType type) +{ + VirtioMemSystemReset *vmem_reset = VIRTIO_MEM_SYSTEM_RESET(obj); + VirtIOMEM *vmem = vmem_reset->vmem; + + /* + * When waking up from standby/suspend-to-ram, do not unplug any memory. + */ + if (type == RESET_TYPE_WAKEUP) { + return; + } + + /* + * During usual resets, we will unplug all memory and shrink the usable + * region size. This is, however, not possible in all scenarios. Then, + * the guest has to deal with this manually (VIRTIO_MEM_REQ_UNPLUG_ALL). + */ + virtio_mem_unplug_all(vmem); +} + +static void virtio_mem_system_reset_class_init(ObjectClass *klass, void *data) +{ + ResettableClass *rc = RESETTABLE_CLASS(klass); + + rc->get_state = virtio_mem_system_reset_get_state; + rc->phases.hold = virtio_mem_system_reset_hold; +} diff --git a/include/hw/virtio/virtio-mem.h b/include/hw/virtio/virtio-mem.h index a1af144c28..abde1c4101 100644 --- a/include/hw/virtio/virtio-mem.h +++ b/include/hw/virtio/virtio-mem.h @@ -25,6 +25,10 @@ OBJECT_DECLARE_TYPE(VirtIOMEM, VirtIOMEMClass, VIRTIO_MEM) +#define TYPE_VIRTIO_MEM_SYSTEM_RESET "virtio-mem-system-reset" + +OBJECT_DECLARE_SIMPLE_TYPE(VirtioMemSystemReset, VIRTIO_MEM_SYSTEM_RESET) + #define VIRTIO_MEM_MEMDEV_PROP "memdev" #define VIRTIO_MEM_NODE_PROP "node" #define VIRTIO_MEM_SIZE_PROP "size" @@ -117,8 +121,14 @@ struct VirtIOMEM { /* listeners to notify on plug/unplug activity. */ QLIST_HEAD(, RamDiscardListener) rdl_list; - /* State of the resettable container */ + /* Catch system resets -> qemu_devices_reset() only. */ + VirtioMemSystemReset *system_reset; +}; + +struct VirtioMemSystemReset { + Object parent; ResettableState reset_state; + VirtIOMEM *vmem; }; struct VirtIOMEMClass {