From patchwork Wed Feb 19 20:34:09 2025 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: "Maciej S. Szmigiero" X-Patchwork-Id: 13982919 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 E7E91C021AA for ; Wed, 19 Feb 2025 20:40:31 +0000 (UTC) Received: from localhost ([::1] helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1tkqot-0000Y9-Ad; Wed, 19 Feb 2025 15:37:23 -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 1tkqoW-0000P6-Cs for qemu-devel@nongnu.org; Wed, 19 Feb 2025 15:37:01 -0500 Received: from vps-ovh.mhejs.net ([145.239.82.108]) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1tkqoT-0004rA-M0 for qemu-devel@nongnu.org; Wed, 19 Feb 2025 15:36:59 -0500 Received: from MUA by vps-ovh.mhejs.net with esmtpsa (TLS1.3) tls TLS_AES_256_GCM_SHA384 (Exim 4.98) (envelope-from ) id 1tkqoF-00000007VVn-2CsT; Wed, 19 Feb 2025 21:36:43 +0100 From: "Maciej S. Szmigiero" To: Peter Xu , Fabiano Rosas Cc: Alex Williamson , =?utf-8?q?C=C3=A9dric_Le_G?= =?utf-8?q?oater?= , Eric Blake , Markus Armbruster , =?utf-8?q?Daniel_P_=2E_Berrang=C3=A9?= , Avihai Horon , Joao Martins , qemu-devel@nongnu.org Subject: [PATCH v5 27/36] vfio/migration: Multifd device state transfer support - load thread Date: Wed, 19 Feb 2025 21:34:09 +0100 Message-ID: <9be8882ea2189c1a827bdf09835d6c65488d2ca6.1739994627.git.maciej.szmigiero@oracle.com> X-Mailer: git-send-email 2.48.1 In-Reply-To: References: MIME-Version: 1.0 Received-SPF: pass client-ip=145.239.82.108; envelope-from=mhej@vps-ovh.mhejs.net; helo=vps-ovh.mhejs.net X-Spam_score_int: -18 X-Spam_score: -1.9 X-Spam_bar: - X-Spam_report: (-1.9 / 5.0 requ) BAYES_00=-1.9, HEADER_FROM_DIFFERENT_DOMAINS=0.001, RCVD_IN_VALIDITY_RPBL_BLOCKED=0.001, RCVD_IN_VALIDITY_SAFE_BLOCKED=0.001, 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 From: "Maciej S. Szmigiero" Since it's important to finish loading device state transferred via the main migration channel (via save_live_iterate SaveVMHandler) before starting loading the data asynchronously transferred via multifd the thread doing the actual loading of the multifd transferred data is only started from switchover_start SaveVMHandler. switchover_start handler is called when MIG_CMD_SWITCHOVER_START sub-command of QEMU_VM_COMMAND is received via the main migration channel. This sub-command is only sent after all save_live_iterate data have already been posted so it is safe to commence loading of the multifd-transferred device state upon receiving it - loading of save_live_iterate data happens synchronously in the main migration thread (much like the processing of MIG_CMD_SWITCHOVER_START) so by the time MIG_CMD_SWITCHOVER_START is processed all the proceeding data must have already been loaded. Signed-off-by: Maciej S. Szmigiero --- hw/vfio/migration-multifd.c | 225 ++++++++++++++++++++++++++++++++++++ hw/vfio/migration-multifd.h | 2 + hw/vfio/migration.c | 12 ++ hw/vfio/trace-events | 5 + 4 files changed, 244 insertions(+) diff --git a/hw/vfio/migration-multifd.c b/hw/vfio/migration-multifd.c index 5d5ee1393674..b3a88c062769 100644 --- a/hw/vfio/migration-multifd.c +++ b/hw/vfio/migration-multifd.c @@ -42,8 +42,13 @@ typedef struct VFIOStateBuffer { } VFIOStateBuffer; typedef struct VFIOMultifd { + QemuThread load_bufs_thread; + bool load_bufs_thread_running; + bool load_bufs_thread_want_exit; + VFIOStateBuffers load_bufs; QemuCond load_bufs_buffer_ready_cond; + QemuCond load_bufs_thread_finished_cond; QemuMutex load_bufs_mutex; /* Lock order: this lock -> BQL */ uint32_t load_buf_idx; uint32_t load_buf_idx_last; @@ -179,6 +184,175 @@ bool vfio_load_state_buffer(void *opaque, char *data, size_t data_size, return true; } +static int vfio_load_bufs_thread_load_config(VFIODevice *vbasedev) +{ + return -EINVAL; +} + +static VFIOStateBuffer *vfio_load_state_buffer_get(VFIOMultifd *multifd) +{ + VFIOStateBuffer *lb; + guint bufs_len; + + bufs_len = vfio_state_buffers_size_get(&multifd->load_bufs); + if (multifd->load_buf_idx >= bufs_len) { + assert(multifd->load_buf_idx == bufs_len); + return NULL; + } + + lb = vfio_state_buffers_at(&multifd->load_bufs, + multifd->load_buf_idx); + if (!lb->is_present) { + return NULL; + } + + return lb; +} + +static bool vfio_load_state_buffer_write(VFIODevice *vbasedev, + VFIOStateBuffer *lb, + Error **errp) +{ + VFIOMigration *migration = vbasedev->migration; + VFIOMultifd *multifd = migration->multifd; + g_autofree char *buf = NULL; + char *buf_cur; + size_t buf_len; + + if (!lb->len) { + return true; + } + + trace_vfio_load_state_device_buffer_load_start(vbasedev->name, + multifd->load_buf_idx); + + /* lb might become re-allocated when we drop the lock */ + buf = g_steal_pointer(&lb->data); + buf_cur = buf; + buf_len = lb->len; + while (buf_len > 0) { + ssize_t wr_ret; + int errno_save; + + /* + * Loading data to the device takes a while, + * drop the lock during this process. + */ + qemu_mutex_unlock(&multifd->load_bufs_mutex); + wr_ret = write(migration->data_fd, buf_cur, buf_len); + errno_save = errno; + qemu_mutex_lock(&multifd->load_bufs_mutex); + + if (wr_ret < 0) { + error_setg(errp, + "writing state buffer %" PRIu32 " failed: %d", + multifd->load_buf_idx, errno_save); + return false; + } + + assert(wr_ret <= buf_len); + buf_len -= wr_ret; + buf_cur += wr_ret; + } + + trace_vfio_load_state_device_buffer_load_end(vbasedev->name, + multifd->load_buf_idx); + + return true; +} + +static bool vfio_load_bufs_thread_want_exit(VFIOMultifd *multifd, + bool *should_quit) +{ + return multifd->load_bufs_thread_want_exit || qatomic_read(should_quit); +} + +/* + * This thread is spawned by vfio_multifd_switchover_start() which gets + * called upon encountering the switchover point marker in main migration + * stream. + * + * It exits after either: + * * completing loading the remaining device state and device config, OR: + * * encountering some error while doing the above, OR: + * * being forcefully aborted by the migration core by it setting should_quit + * or by vfio_load_cleanup_load_bufs_thread() setting + * multifd->load_bufs_thread_want_exit. + */ +static bool vfio_load_bufs_thread(void *opaque, bool *should_quit, Error **errp) +{ + VFIODevice *vbasedev = opaque; + VFIOMigration *migration = vbasedev->migration; + VFIOMultifd *multifd = migration->multifd; + bool ret = true; + int config_ret; + + assert(multifd); + QEMU_LOCK_GUARD(&multifd->load_bufs_mutex); + + assert(multifd->load_bufs_thread_running); + + while (true) { + VFIOStateBuffer *lb; + + /* + * Always check cancellation first after the buffer_ready wait below in + * case that cond was signalled by vfio_load_cleanup_load_bufs_thread(). + */ + if (vfio_load_bufs_thread_want_exit(multifd, should_quit)) { + error_setg(errp, "operation cancelled"); + ret = false; + goto ret_signal; + } + + assert(multifd->load_buf_idx <= multifd->load_buf_idx_last); + + lb = vfio_load_state_buffer_get(multifd); + if (!lb) { + trace_vfio_load_state_device_buffer_starved(vbasedev->name, + multifd->load_buf_idx); + qemu_cond_wait(&multifd->load_bufs_buffer_ready_cond, + &multifd->load_bufs_mutex); + continue; + } + + if (multifd->load_buf_idx == multifd->load_buf_idx_last) { + break; + } + + if (multifd->load_buf_idx == 0) { + trace_vfio_load_state_device_buffer_start(vbasedev->name); + } + + if (!vfio_load_state_buffer_write(vbasedev, lb, errp)) { + ret = false; + goto ret_signal; + } + + if (multifd->load_buf_idx == multifd->load_buf_idx_last - 1) { + trace_vfio_load_state_device_buffer_end(vbasedev->name); + } + + multifd->load_buf_idx++; + } + + config_ret = vfio_load_bufs_thread_load_config(vbasedev); + if (config_ret) { + error_setg(errp, "load config state failed: %d", config_ret); + ret = false; + } + +ret_signal: + /* + * Notify possibly waiting vfio_load_cleanup_load_bufs_thread() that + * this thread is exiting. + */ + multifd->load_bufs_thread_running = false; + qemu_cond_signal(&multifd->load_bufs_thread_finished_cond); + + return ret; +} + VFIOMultifd *vfio_multifd_new(void) { VFIOMultifd *multifd = g_new(VFIOMultifd, 1); @@ -191,11 +365,42 @@ VFIOMultifd *vfio_multifd_new(void) multifd->load_buf_idx_last = UINT32_MAX; qemu_cond_init(&multifd->load_bufs_buffer_ready_cond); + multifd->load_bufs_thread_running = false; + multifd->load_bufs_thread_want_exit = false; + qemu_cond_init(&multifd->load_bufs_thread_finished_cond); + return multifd; } +/* + * Terminates vfio_load_bufs_thread by setting + * multifd->load_bufs_thread_want_exit and signalling all the conditions + * the thread could be blocked on. + * + * Waits for the thread to signal that it had finished. + */ +static void vfio_load_cleanup_load_bufs_thread(VFIOMultifd *multifd) +{ + /* The lock order is load_bufs_mutex -> BQL so unlock BQL here first */ + bql_unlock(); + WITH_QEMU_LOCK_GUARD(&multifd->load_bufs_mutex) { + while (multifd->load_bufs_thread_running) { + multifd->load_bufs_thread_want_exit = true; + + qemu_cond_signal(&multifd->load_bufs_buffer_ready_cond); + qemu_cond_wait(&multifd->load_bufs_thread_finished_cond, + &multifd->load_bufs_mutex); + } + } + bql_lock(); +} + void vfio_multifd_free(VFIOMultifd *multifd) { + vfio_load_cleanup_load_bufs_thread(multifd); + + qemu_cond_destroy(&multifd->load_bufs_thread_finished_cond); + vfio_state_buffers_destroy(&multifd->load_bufs); qemu_cond_destroy(&multifd->load_bufs_buffer_ready_cond); qemu_mutex_destroy(&multifd->load_bufs_mutex); @@ -225,3 +430,23 @@ bool vfio_multifd_transfer_setup(VFIODevice *vbasedev, Error **errp) return true; } + +int vfio_multifd_switchover_start(VFIODevice *vbasedev) +{ + VFIOMigration *migration = vbasedev->migration; + VFIOMultifd *multifd = migration->multifd; + + assert(multifd); + + /* The lock order is load_bufs_mutex -> BQL so unlock BQL here first */ + bql_unlock(); + WITH_QEMU_LOCK_GUARD(&multifd->load_bufs_mutex) { + assert(!multifd->load_bufs_thread_running); + multifd->load_bufs_thread_running = true; + } + bql_lock(); + + qemu_loadvm_start_load_thread(vfio_load_bufs_thread, vbasedev); + + return 0; +} diff --git a/hw/vfio/migration-multifd.h b/hw/vfio/migration-multifd.h index d5ab7d6f85f5..09cbb437d9d1 100644 --- a/hw/vfio/migration-multifd.h +++ b/hw/vfio/migration-multifd.h @@ -25,4 +25,6 @@ bool vfio_multifd_transfer_setup(VFIODevice *vbasedev, Error **errp); bool vfio_load_state_buffer(void *opaque, char *data, size_t data_size, Error **errp); +int vfio_multifd_switchover_start(VFIODevice *vbasedev); + #endif diff --git a/hw/vfio/migration.c b/hw/vfio/migration.c index abaf4d08d4a9..85f54cb22df2 100644 --- a/hw/vfio/migration.c +++ b/hw/vfio/migration.c @@ -793,6 +793,17 @@ static bool vfio_switchover_ack_needed(void *opaque) return vfio_precopy_supported(vbasedev); } +static int vfio_switchover_start(void *opaque) +{ + VFIODevice *vbasedev = opaque; + + if (vfio_multifd_transfer_enabled(vbasedev)) { + return vfio_multifd_switchover_start(vbasedev); + } + + return 0; +} + static const SaveVMHandlers savevm_vfio_handlers = { .save_prepare = vfio_save_prepare, .save_setup = vfio_save_setup, @@ -808,6 +819,7 @@ static const SaveVMHandlers savevm_vfio_handlers = { .load_state = vfio_load_state, .load_state_buffer = vfio_load_state_buffer, .switchover_ack_needed = vfio_switchover_ack_needed, + .switchover_start = vfio_switchover_start, }; /* ---------------------------------------------------------------------- */ diff --git a/hw/vfio/trace-events b/hw/vfio/trace-events index 042a3dc54a33..418b378ebd29 100644 --- a/hw/vfio/trace-events +++ b/hw/vfio/trace-events @@ -154,6 +154,11 @@ vfio_load_device_config_state_end(const char *name) " (%s)" vfio_load_state(const char *name, uint64_t data) " (%s) data 0x%"PRIx64 vfio_load_state_device_data(const char *name, uint64_t data_size, int ret) " (%s) size %"PRIu64" ret %d" vfio_load_state_device_buffer_incoming(const char *name, uint32_t idx) " (%s) idx %"PRIu32 +vfio_load_state_device_buffer_start(const char *name) " (%s)" +vfio_load_state_device_buffer_starved(const char *name, uint32_t idx) " (%s) idx %"PRIu32 +vfio_load_state_device_buffer_load_start(const char *name, uint32_t idx) " (%s) idx %"PRIu32 +vfio_load_state_device_buffer_load_end(const char *name, uint32_t idx) " (%s) idx %"PRIu32 +vfio_load_state_device_buffer_end(const char *name) " (%s)" vfio_migration_realize(const char *name) " (%s)" vfio_migration_set_device_state(const char *name, const char *state) " (%s) state %s" vfio_migration_set_state(const char *name, const char *new_state, const char *recover_state) " (%s) new state %s, recover state %s"