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Wed, 22 Feb 2023 09:49:39 -0800 Received: from rnnvmail205.nvidia.com (10.129.68.10) by rnnvmail204.nvidia.com (10.129.68.6) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.2.986.36; Wed, 22 Feb 2023 09:49:38 -0800 Received: from vdi.nvidia.com (10.127.8.9) by mail.nvidia.com (10.129.68.10) with Microsoft SMTP Server id 15.2.986.36 via Frontend Transport; Wed, 22 Feb 2023 09:49:33 -0800 From: Avihai Horon To: CC: Alex Williamson , =?utf-8?q?C=C3=A9dric_Le_G?= =?utf-8?q?oater?= , Juan Quintela , "Dr. David Alan Gilbert" , "Michael S. Tsirkin" , Peter Xu , "Jason Wang" , Marcel Apfelbaum , Paolo Bonzini , Richard Henderson , Eduardo Habkost , "David Hildenbrand" , =?utf-8?q?Philippe_Mathieu-Daud?= =?utf-8?q?=C3=A9?= , Yishai Hadas , Jason Gunthorpe , Maor Gottlieb , Avihai Horon , Kirti Wankhede , Tarun Gupta , Joao Martins Subject: [PATCH v2 03/20] vfio/migration: Add VFIO migration pre-copy support Date: Wed, 22 Feb 2023 19:48:58 +0200 Message-ID: <20230222174915.5647-4-avihaih@nvidia.com> X-Mailer: git-send-email 2.21.3 In-Reply-To: <20230222174915.5647-1-avihaih@nvidia.com> References: <20230222174915.5647-1-avihaih@nvidia.com> MIME-Version: 1.0 X-EOPAttributedMessage: 0 X-MS-PublicTrafficType: Email X-MS-TrafficTypeDiagnostic: CO1NAM11FT111:EE_|DS7PR12MB6093:EE_ X-MS-Office365-Filtering-Correlation-Id: c407ab97-4a88-4cc3-f5ed-08db14fd3bc7 X-MS-Exchange-SenderADCheck: 1 X-MS-Exchange-AntiSpam-Relay: 0 X-Microsoft-Antispam: BCL:0; X-Microsoft-Antispam-Message-Info: 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 X-Forefront-Antispam-Report: CIP:216.228.117.160; CTRY:US; LANG:en; SCL:1; SRV:; IPV:NLI; SFV:NSPM; H:mail.nvidia.com; PTR:dc6edge1.nvidia.com; CAT:NONE; SFS:(13230025)(4636009)(396003)(136003)(39860400002)(376002)(346002)(451199018)(5400799012)(46966006)(40470700004)(36840700001)(26005)(186003)(82310400005)(336012)(36756003)(7696005)(2616005)(6916009)(478600001)(86362001)(426003)(47076005)(966005)(6666004)(83380400001)(8676002)(70206006)(70586007)(1076003)(316002)(54906003)(4326008)(41300700001)(7416002)(36860700001)(8936002)(5660300002)(34020700004)(30864003)(82740400003)(40480700001)(2906002)(7636003)(40460700003)(356005)(12100799015); DIR:OUT; SFP:1501; X-OriginatorOrg: Nvidia.com X-MS-Exchange-CrossTenant-OriginalArrivalTime: 22 Feb 2023 17:50:06.4359 (UTC) X-MS-Exchange-CrossTenant-Network-Message-Id: c407ab97-4a88-4cc3-f5ed-08db14fd3bc7 X-MS-Exchange-CrossTenant-Id: 43083d15-7273-40c1-b7db-39efd9ccc17a X-MS-Exchange-CrossTenant-OriginalAttributedTenantConnectingIp: TenantId=43083d15-7273-40c1-b7db-39efd9ccc17a; Ip=[216.228.117.160]; Helo=[mail.nvidia.com] X-MS-Exchange-CrossTenant-AuthSource: CO1NAM11FT111.eop-nam11.prod.protection.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Anonymous X-MS-Exchange-CrossTenant-FromEntityHeader: HybridOnPrem X-MS-Exchange-Transport-CrossTenantHeadersStamped: DS7PR12MB6093 Received-SPF: softfail client-ip=2a01:111:f400:7e89::307; envelope-from=avihaih@nvidia.com; helo=NAM10-MW2-obe.outbound.protection.outlook.com X-Spam_score_int: -20 X-Spam_score: -2.1 X-Spam_bar: -- X-Spam_report: (-2.1 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.001, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, SPF_HELO_PASS=-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 Pre-copy support allows the VFIO device data to be transferred while the VM is running. This helps to accommodate VFIO devices that have a large amount of data that needs to be transferred, and it can reduce migration downtime. Pre-copy support is optional in VFIO migration protocol v2. Implement pre-copy of VFIO migration protocol v2 and use it for devices that support it. Full description of it can be found here [1]. [1] https://lore.kernel.org/kvm/20221206083438.37807-3-yishaih@nvidia.com/ Signed-off-by: Avihai Horon --- docs/devel/vfio-migration.rst | 35 +++++-- include/hw/vfio/vfio-common.h | 3 + hw/vfio/common.c | 6 +- hw/vfio/migration.c | 175 ++++++++++++++++++++++++++++++++-- hw/vfio/trace-events | 4 +- 5 files changed, 201 insertions(+), 22 deletions(-) diff --git a/docs/devel/vfio-migration.rst b/docs/devel/vfio-migration.rst index c214c73e28..ba80b9150d 100644 --- a/docs/devel/vfio-migration.rst +++ b/docs/devel/vfio-migration.rst @@ -7,12 +7,14 @@ the guest is running on source host and restoring this saved state on the destination host. This document details how saving and restoring of VFIO devices is done in QEMU. -Migration of VFIO devices currently consists of a single stop-and-copy phase. -During the stop-and-copy phase the guest is stopped and the entire VFIO device -data is transferred to the destination. - -The pre-copy phase of migration is currently not supported for VFIO devices. -Support for VFIO pre-copy will be added later on. +Migration of VFIO devices consists of two phases: the optional pre-copy phase, +and the stop-and-copy phase. The pre-copy phase is iterative and allows to +accommodate VFIO devices that have a large amount of data that needs to be +transferred. The iterative pre-copy phase of migration allows for the guest to +continue whilst the VFIO device state is transferred to the destination, this +helps to reduce the total downtime of the VM. VFIO devices can choose to skip +the pre-copy phase of migration by not reporting the VFIO_MIGRATION_PRE_COPY +flag in VFIO_DEVICE_FEATURE_MIGRATION ioctl. Note that currently VFIO migration is supported only for a single device. This is due to VFIO migration's lack of P2P support. However, P2P support is planned @@ -29,10 +31,20 @@ VFIO implements the device hooks for the iterative approach as follows: * A ``load_setup`` function that sets the VFIO device on the destination in _RESUMING state. +* A ``state_pending_estimate`` function that reports an estimate of the + remaining pre-copy data that the vendor driver has yet to save for the VFIO + device. + * A ``state_pending_exact`` function that reads pending_bytes from the vendor driver, which indicates the amount of data that the vendor driver has yet to save for the VFIO device. +* An ``is_active_iterate`` function that indicates ``save_live_iterate`` is + active only when the VFIO device is in pre-copy states. + +* A ``save_live_iterate`` function that reads the VFIO device's data from the + vendor driver during iterative pre-copy phase. + * A ``save_state`` function to save the device config space if it is present. * A ``save_live_complete_precopy`` function that sets the VFIO device in @@ -95,8 +107,10 @@ Flow of state changes during Live migration =========================================== Below is the flow of state change during live migration. -The values in the brackets represent the VM state, the migration state, and +The values in the parentheses represent the VM state, the migration state, and the VFIO device state, respectively. +The text in the square brackets represents the flow if the VFIO device supports +pre-copy. Live migration save path ------------------------ @@ -108,11 +122,12 @@ Live migration save path | migrate_init spawns migration_thread Migration thread then calls each device's .save_setup() - (RUNNING, _SETUP, _RUNNING) + (RUNNING, _SETUP, _RUNNING [_PRE_COPY]) | - (RUNNING, _ACTIVE, _RUNNING) - If device is active, get pending_bytes by .state_pending_exact() + (RUNNING, _ACTIVE, _RUNNING [_PRE_COPY]) + If device is active, get pending_bytes by .state_pending_{estimate,exact}() If total pending_bytes >= threshold_size, call .save_live_iterate() + [Data of VFIO device for pre-copy phase is copied] Iterate till total pending bytes converge and are less than threshold | On migration completion, vCPU stops and calls .save_live_complete_precopy for diff --git a/include/hw/vfio/vfio-common.h b/include/hw/vfio/vfio-common.h index 87524c64a4..ee55d442b4 100644 --- a/include/hw/vfio/vfio-common.h +++ b/include/hw/vfio/vfio-common.h @@ -66,6 +66,9 @@ typedef struct VFIOMigration { int data_fd; void *data_buffer; size_t data_buffer_size; + uint64_t precopy_init_size; + uint64_t precopy_dirty_size; + uint64_t mig_flags; } VFIOMigration; typedef struct VFIOAddressSpace { diff --git a/hw/vfio/common.c b/hw/vfio/common.c index bab83c0e55..6f5afe9f5a 100644 --- a/hw/vfio/common.c +++ b/hw/vfio/common.c @@ -409,7 +409,8 @@ static bool vfio_devices_all_dirty_tracking(VFIOContainer *container) } if (vbasedev->pre_copy_dirty_page_tracking == ON_OFF_AUTO_OFF && - migration->device_state == VFIO_DEVICE_STATE_RUNNING) { + (migration->device_state == VFIO_DEVICE_STATE_RUNNING || + migration->device_state == VFIO_DEVICE_STATE_PRE_COPY)) { return false; } } @@ -438,7 +439,8 @@ static bool vfio_devices_all_running_and_mig_active(VFIOContainer *container) return false; } - if (migration->device_state == VFIO_DEVICE_STATE_RUNNING) { + if (migration->device_state == VFIO_DEVICE_STATE_RUNNING || + migration->device_state == VFIO_DEVICE_STATE_PRE_COPY) { continue; } else { return false; diff --git a/hw/vfio/migration.c b/hw/vfio/migration.c index 94a4df73d0..307983d57d 100644 --- a/hw/vfio/migration.c +++ b/hw/vfio/migration.c @@ -67,6 +67,8 @@ static const char *mig_state_to_str(enum vfio_device_mig_state state) return "STOP_COPY"; case VFIO_DEVICE_STATE_RESUMING: return "RESUMING"; + case VFIO_DEVICE_STATE_PRE_COPY: + return "PRE_COPY"; default: return "UNKNOWN STATE"; } @@ -240,6 +242,23 @@ static int vfio_query_stop_copy_size(VFIODevice *vbasedev, return 0; } +static int vfio_query_precopy_size(VFIOMigration *migration, + uint64_t *init_size, uint64_t *dirty_size) +{ + struct vfio_precopy_info precopy = { + .argsz = sizeof(precopy), + }; + + if (ioctl(migration->data_fd, VFIO_MIG_GET_PRECOPY_INFO, &precopy)) { + return -errno; + } + + *init_size = precopy.initial_bytes; + *dirty_size = precopy.dirty_bytes; + + return 0; +} + /* Returns the size of saved data on success and -errno on error */ static ssize_t vfio_save_block(QEMUFile *f, VFIOMigration *migration) { @@ -248,6 +267,11 @@ static ssize_t vfio_save_block(QEMUFile *f, VFIOMigration *migration) data_size = read(migration->data_fd, migration->data_buffer, migration->data_buffer_size); if (data_size < 0) { + /* Pre-copy emptied all the device state for now */ + if (errno == ENOMSG) { + return 0; + } + return -errno; } if (data_size == 0) { @@ -264,6 +288,31 @@ static ssize_t vfio_save_block(QEMUFile *f, VFIOMigration *migration) return qemu_file_get_error(f) ?: data_size; } +static void vfio_update_estimated_pending_data(VFIOMigration *migration, + uint64_t data_size) +{ + if (!data_size) { + /* + * Pre-copy emptied all the device state for now, update estimated sizes + * accordingly. + */ + migration->precopy_init_size = 0; + migration->precopy_dirty_size = 0; + + return; + } + + if (migration->precopy_init_size) { + uint64_t init_size = MIN(migration->precopy_init_size, data_size); + + migration->precopy_init_size -= init_size; + data_size -= init_size; + } + + migration->precopy_dirty_size -= MIN(migration->precopy_dirty_size, + data_size); +} + /* ---------------------------------------------------------------------- */ static int vfio_save_setup(QEMUFile *f, void *opaque) @@ -284,6 +333,35 @@ static int vfio_save_setup(QEMUFile *f, void *opaque) return -ENOMEM; } + if (migration->mig_flags & VFIO_MIGRATION_PRE_COPY) { + uint64_t init_size = 0, dirty_size = 0; + int ret; + + switch (migration->device_state) { + case VFIO_DEVICE_STATE_RUNNING: + ret = vfio_migration_set_state(vbasedev, VFIO_DEVICE_STATE_PRE_COPY, + VFIO_DEVICE_STATE_RUNNING); + if (ret) { + return ret; + } + + vfio_query_precopy_size(migration, &init_size, &dirty_size); + migration->precopy_init_size = init_size; + migration->precopy_dirty_size = dirty_size; + + break; + case VFIO_DEVICE_STATE_STOP: + /* vfio_save_complete_precopy() will go to STOP_COPY */ + + migration->precopy_init_size = 0; + migration->precopy_dirty_size = 0; + + break; + default: + return -EINVAL; + } + } + trace_vfio_save_setup(vbasedev->name, migration->data_buffer_size); qemu_put_be64(f, VFIO_MIG_FLAG_END_OF_STATE); @@ -302,23 +380,44 @@ static void vfio_save_cleanup(void *opaque) trace_vfio_save_cleanup(vbasedev->name); } +static void vfio_state_pending_estimate(void *opaque, uint64_t threshold_size, + uint64_t *must_precopy, + uint64_t *can_postcopy) +{ + VFIODevice *vbasedev = opaque; + VFIOMigration *migration = vbasedev->migration; + + if (migration->device_state != VFIO_DEVICE_STATE_PRE_COPY) { + return; + } + + /* + * Initial size should be transferred during pre-copy phase so stop-copy + * phase will not be slowed down. Report threshold_size to force another + * pre-copy iteration. + */ + *must_precopy += migration->precopy_init_size ? + threshold_size : + migration->precopy_dirty_size; + + trace_vfio_state_pending_estimate(vbasedev->name, *must_precopy, + *can_postcopy, + migration->precopy_init_size, + migration->precopy_dirty_size); +} + /* * Migration size of VFIO devices can be as little as a few KBs or as big as * many GBs. This value should be big enough to cover the worst case. */ #define VFIO_MIG_STOP_COPY_SIZE (100 * GiB) -/* - * Only exact function is implemented and not estimate function. The reason is - * that during pre-copy phase of migration the estimate function is called - * repeatedly while pending RAM size is over the threshold, thus migration - * can't converge and querying the VFIO device pending data size is useless. - */ static void vfio_state_pending_exact(void *opaque, uint64_t threshold_size, uint64_t *must_precopy, uint64_t *can_postcopy) { VFIODevice *vbasedev = opaque; + VFIOMigration *migration = vbasedev->migration; uint64_t stop_copy_size = VFIO_MIG_STOP_COPY_SIZE; /* @@ -328,8 +427,57 @@ static void vfio_state_pending_exact(void *opaque, uint64_t threshold_size, vfio_query_stop_copy_size(vbasedev, &stop_copy_size); *must_precopy += stop_copy_size; + if (migration->device_state == VFIO_DEVICE_STATE_PRE_COPY) { + uint64_t init_size = 0, dirty_size = 0; + + vfio_query_precopy_size(migration, &init_size, &dirty_size); + migration->precopy_init_size = init_size; + migration->precopy_dirty_size = dirty_size; + + /* + * Initial size should be transferred during pre-copy phase so + * stop-copy phase will not be slowed down. Report threshold_size + * to force another pre-copy iteration. + */ + *must_precopy += migration->precopy_init_size ? + threshold_size : + migration->precopy_dirty_size; + } + trace_vfio_state_pending_exact(vbasedev->name, *must_precopy, *can_postcopy, - stop_copy_size); + stop_copy_size, migration->precopy_init_size, + migration->precopy_dirty_size); +} + +static bool vfio_is_active_iterate(void *opaque) +{ + VFIODevice *vbasedev = opaque; + VFIOMigration *migration = vbasedev->migration; + + return migration->device_state == VFIO_DEVICE_STATE_PRE_COPY; +} + +static int vfio_save_iterate(QEMUFile *f, void *opaque) +{ + VFIODevice *vbasedev = opaque; + VFIOMigration *migration = vbasedev->migration; + ssize_t data_size; + + data_size = vfio_save_block(f, migration); + if (data_size < 0) { + return data_size; + } + qemu_put_be64(f, VFIO_MIG_FLAG_END_OF_STATE); + + vfio_update_estimated_pending_data(migration, data_size); + + trace_vfio_save_iterate(vbasedev->name); + + /* + * A VFIO device's pre-copy dirty_bytes is not guaranteed to reach zero. + * Return 1 so following handlers will not be potentially blocked. + */ + return 1; } static int vfio_save_complete_precopy(QEMUFile *f, void *opaque) @@ -338,7 +486,7 @@ static int vfio_save_complete_precopy(QEMUFile *f, void *opaque) ssize_t data_size; int ret; - /* We reach here with device state STOP only */ + /* We reach here with device state STOP or STOP_COPY only */ ret = vfio_migration_set_state(vbasedev, VFIO_DEVICE_STATE_STOP_COPY, VFIO_DEVICE_STATE_STOP); if (ret) { @@ -457,7 +605,10 @@ static int vfio_load_state(QEMUFile *f, void *opaque, int version_id) static const SaveVMHandlers savevm_vfio_handlers = { .save_setup = vfio_save_setup, .save_cleanup = vfio_save_cleanup, + .state_pending_estimate = vfio_state_pending_estimate, .state_pending_exact = vfio_state_pending_exact, + .is_active_iterate = vfio_is_active_iterate, + .save_live_iterate = vfio_save_iterate, .save_live_complete_precopy = vfio_save_complete_precopy, .save_state = vfio_save_state, .load_setup = vfio_load_setup, @@ -470,13 +621,18 @@ static const SaveVMHandlers savevm_vfio_handlers = { static void vfio_vmstate_change(void *opaque, bool running, RunState state) { VFIODevice *vbasedev = opaque; + VFIOMigration *migration = vbasedev->migration; enum vfio_device_mig_state new_state; int ret; if (running) { new_state = VFIO_DEVICE_STATE_RUNNING; } else { - new_state = VFIO_DEVICE_STATE_STOP; + new_state = + (migration->device_state == VFIO_DEVICE_STATE_PRE_COPY && + (state == RUN_STATE_FINISH_MIGRATE || state == RUN_STATE_PAUSED)) ? + VFIO_DEVICE_STATE_STOP_COPY : + VFIO_DEVICE_STATE_STOP; } /* @@ -590,6 +746,7 @@ static int vfio_migration_init(VFIODevice *vbasedev) migration->vbasedev = vbasedev; migration->device_state = VFIO_DEVICE_STATE_RUNNING; migration->data_fd = -1; + migration->mig_flags = mig_flags; oid = vmstate_if_get_id(VMSTATE_IF(DEVICE(obj))); if (oid) { diff --git a/hw/vfio/trace-events b/hw/vfio/trace-events index 669d9fe07c..51613e02e6 100644 --- a/hw/vfio/trace-events +++ b/hw/vfio/trace-events @@ -161,6 +161,8 @@ vfio_save_block(const char *name, int data_size) " (%s) data_size %d" vfio_save_cleanup(const char *name) " (%s)" vfio_save_complete_precopy(const char *name, int ret) " (%s) ret %d" vfio_save_device_config_state(const char *name) " (%s)" +vfio_save_iterate(const char *name) " (%s)" vfio_save_setup(const char *name, uint64_t data_buffer_size) " (%s) data buffer size 0x%"PRIx64 -vfio_state_pending_exact(const char *name, uint64_t precopy, uint64_t postcopy, uint64_t stopcopy_size) " (%s) precopy 0x%"PRIx64" postcopy 0x%"PRIx64" stopcopy size 0x%"PRIx64 +vfio_state_pending_estimate(const char *name, uint64_t precopy, uint64_t postcopy, uint64_t precopy_init_size, uint64_t precopy_dirty_size) " (%s) precopy 0x%"PRIx64" postcopy 0x%"PRIx64" precopy initial size 0x%"PRIx64" precopy dirty size 0x%"PRIx64 +vfio_state_pending_exact(const char *name, uint64_t precopy, uint64_t postcopy, uint64_t stopcopy_size, uint64_t precopy_init_size, uint64_t precopy_dirty_size) " (%s) precopy 0x%"PRIx64" postcopy 0x%"PRIx64" stopcopy size 0x%"PRIx64" precopy initial size 0x%"PRIx64" precopy dirty size 0x%"PRIx64 vfio_vmstate_change(const char *name, int running, const char *reason, const char *dev_state) " (%s) running %d reason %s device state %s"