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[99.254.121.117]) by smtp.gmail.com with ESMTPSA id d6-20020a0ce446000000b00690cec16254sm1541932qvm.68.2024.03.11.14.59.35 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 11 Mar 2024 14:59:36 -0700 (PDT) From: peterx@redhat.com To: qemu-devel@nongnu.org, Peter Maydell Cc: Paolo Bonzini , peterx@redhat.com, Fabiano Rosas , David Hildenbrand , Prasad Pandit , =?utf-8?q?C=C3=A9dric_Le_Goater?= Subject: [PULL 07/34] migration: Add documentation for SaveVMHandlers Date: Mon, 11 Mar 2024 17:58:58 -0400 Message-ID: <20240311215925.40618-8-peterx@redhat.com> X-Mailer: git-send-email 2.44.0 In-Reply-To: <20240311215925.40618-1-peterx@redhat.com> References: <20240311215925.40618-1-peterx@redhat.com> MIME-Version: 1.0 Received-SPF: pass client-ip=170.10.129.124; envelope-from=peterx@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: -30 X-Spam_score: -3.1 X-Spam_bar: --- X-Spam_report: (-3.1 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-1.029, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_NONE=-0.0001, SPF_HELO_NONE=0.001, SPF_PASS=-0.001, T_SCC_BODY_TEXT_LINE=-0.01 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: Cédric Le Goater The SaveVMHandlers structure is still in use for complex subsystems and devices. Document the handlers since we are going to modify a few later. Reviewed-by: Peter Xu Signed-off-by: Cédric Le Goater Link: https://lore.kernel.org/r/20240304122844.1888308-9-clg@redhat.com Signed-off-by: Peter Xu --- include/migration/register.h | 263 +++++++++++++++++++++++++++++++---- 1 file changed, 237 insertions(+), 26 deletions(-) diff --git a/include/migration/register.h b/include/migration/register.h index 2e6a7d766e..d7b70a8be6 100644 --- a/include/migration/register.h +++ b/include/migration/register.h @@ -16,30 +16,130 @@ #include "hw/vmstate-if.h" +/** + * struct SaveVMHandlers: handler structure to finely control + * migration of complex subsystems and devices, such as RAM, block and + * VFIO. + */ typedef struct SaveVMHandlers { - /* This runs inside the BQL. */ + + /* The following handlers run inside the BQL. */ + + /** + * @save_state + * + * Saves state section on the source using the latest state format + * version. + * + * Legacy method. Should be deprecated when all users are ported + * to VMStateDescription. + * + * @f: QEMUFile where to send the data + * @opaque: data pointer passed to register_savevm_live() + */ void (*save_state)(QEMUFile *f, void *opaque); - /* - * save_prepare is called early, even before migration starts, and can be - * used to perform early checks. + /** + * @save_prepare + * + * Called early, even before migration starts, and can be used to + * perform early checks. + * + * @opaque: data pointer passed to register_savevm_live() + * @errp: pointer to Error*, to store an error if it happens. + * + * Returns zero to indicate success and negative for error */ int (*save_prepare)(void *opaque, Error **errp); + + /** + * @save_setup + * + * Initializes the data structures on the source and transmits + * first section containing information on the device + * + * @f: QEMUFile where to send the data + * @opaque: data pointer passed to register_savevm_live() + * + * Returns zero to indicate success and negative for error + */ int (*save_setup)(QEMUFile *f, void *opaque); + + /** + * @save_cleanup + * + * Uninitializes the data structures on the source + * + * @opaque: data pointer passed to register_savevm_live() + */ void (*save_cleanup)(void *opaque); + + /** + * @save_live_complete_postcopy + * + * Called at the end of postcopy for all postcopyable devices. + * + * @f: QEMUFile where to send the data + * @opaque: data pointer passed to register_savevm_live() + * + * Returns zero to indicate success and negative for error + */ int (*save_live_complete_postcopy)(QEMUFile *f, void *opaque); + + /** + * @save_live_complete_precopy + * + * Transmits the last section for the device containing any + * remaining data at the end of a precopy phase. When postcopy is + * enabled, devices that support postcopy will skip this step, + * where the final data will be flushed at the end of postcopy via + * @save_live_complete_postcopy instead. + * + * @f: QEMUFile where to send the data + * @opaque: data pointer passed to register_savevm_live() + * + * Returns zero to indicate success and negative for error + */ int (*save_live_complete_precopy)(QEMUFile *f, void *opaque); /* This runs both outside and inside the BQL. */ + + /** + * @is_active + * + * Will skip a state section if not active + * + * @opaque: data pointer passed to register_savevm_live() + * + * Returns true if state section is active else false + */ bool (*is_active)(void *opaque); + + /** + * @has_postcopy + * + * Checks if a device supports postcopy + * + * @opaque: data pointer passed to register_savevm_live() + * + * Returns true for postcopy support else false + */ bool (*has_postcopy)(void *opaque); - /* is_active_iterate - * If it is not NULL then qemu_savevm_state_iterate will skip iteration if - * it returns false. For example, it is needed for only-postcopy-states, - * which needs to be handled by qemu_savevm_state_setup and - * qemu_savevm_state_pending, but do not need iterations until not in - * postcopy stage. + /** + * @is_active_iterate + * + * As #SaveVMHandlers.is_active(), will skip an inactive state + * section in qemu_savevm_state_iterate. + * + * For example, it is needed for only-postcopy-states, which needs + * to be handled by qemu_savevm_state_setup() and + * qemu_savevm_state_pending(), but do not need iterations until + * not in postcopy stage. + * + * @opaque: data pointer passed to register_savevm_live() + * + * Returns true if state section is active else false */ bool (*is_active_iterate)(void *opaque); @@ -48,44 +148,155 @@ typedef struct SaveVMHandlers { * use data that is local to the migration thread or protected * by other locks. */ + + /** + * @save_live_iterate + * + * Should send a chunk of data until the point that stream + * bandwidth limits tell it to stop. Each call generates one + * section. + * + * @f: QEMUFile where to send the data + * @opaque: data pointer passed to register_savevm_live() + * + * Returns 0 to indicate that there is still more data to send, + * 1 that there is no more data to send and + * negative to indicate an error. + */ int (*save_live_iterate)(QEMUFile *f, void *opaque); /* This runs outside the BQL! */ - /* Note for save_live_pending: - * must_precopy: - * - must be migrated in precopy or in stopped state - * - i.e. must be migrated before target start - * - * can_postcopy: - * - can migrate in postcopy or in stopped state - * - i.e. can migrate after target start - * - some can also be migrated during precopy (RAM) - * - some must be migrated after source stops (block-dirty-bitmap) - * - * Sum of can_postcopy and must_postcopy is the whole amount of + + /** + * @state_pending_estimate + * + * This estimates the remaining data to transfer + * + * Sum of @can_postcopy and @must_postcopy is the whole amount of * pending data. + * + * @opaque: data pointer passed to register_savevm_live() + * @must_precopy: amount of data that must be migrated in precopy + * or in stopped state, i.e. that must be migrated + * before target start. + * @can_postcopy: amount of data that can be migrated in postcopy + * or in stopped state, i.e. after target start. + * Some can also be migrated during precopy (RAM). + * Some must be migrated after source stops + * (block-dirty-bitmap) */ - /* This estimates the remaining data to transfer */ void (*state_pending_estimate)(void *opaque, uint64_t *must_precopy, uint64_t *can_postcopy); - /* This calculate the exact remaining data to transfer */ + + /** + * @state_pending_exact + * + * This calculates the exact remaining data to transfer + * + * Sum of @can_postcopy and @must_postcopy is the whole amount of + * pending data. + * + * @opaque: data pointer passed to register_savevm_live() + * @must_precopy: amount of data that must be migrated in precopy + * or in stopped state, i.e. that must be migrated + * before target start. + * @can_postcopy: amount of data that can be migrated in postcopy + * or in stopped state, i.e. after target start. + * Some can also be migrated during precopy (RAM). + * Some must be migrated after source stops + * (block-dirty-bitmap) + */ void (*state_pending_exact)(void *opaque, uint64_t *must_precopy, uint64_t *can_postcopy); + + /** + * @load_state + * + * Load sections generated by any of the save functions that + * generate sections. + * + * Legacy method. Should be deprecated when all users are ported + * to VMStateDescription. + * + * @f: QEMUFile where to receive the data + * @opaque: data pointer passed to register_savevm_live() + * @version_id: the maximum version_id supported + * + * Returns zero to indicate success and negative for error + */ int (*load_state)(QEMUFile *f, void *opaque, int version_id); + + /** + * @load_setup + * + * Initializes the data structures on the destination. + * + * @f: QEMUFile where to receive the data + * @opaque: data pointer passed to register_savevm_live() + * + * Returns zero to indicate success and negative for error + */ int (*load_setup)(QEMUFile *f, void *opaque); + + /** + * @load_cleanup + * + * Uninitializes the data structures on the destination. + * + * @opaque: data pointer passed to register_savevm_live() + * + * Returns zero to indicate success and negative for error + */ int (*load_cleanup)(void *opaque); - /* Called when postcopy migration wants to resume from failure */ + + /** + * @resume_prepare + * + * Called when postcopy migration wants to resume from failure + * + * @s: Current migration state + * @opaque: data pointer passed to register_savevm_live() + * + * Returns zero to indicate success and negative for error + */ int (*resume_prepare)(MigrationState *s, void *opaque); - /* Checks if switchover ack should be used. Called only in dest */ + + /** + * @switchover_ack_needed + * + * Checks if switchover ack should be used. Called only on + * destination. + * + * @opaque: data pointer passed to register_savevm_live() + * + * Returns true if switchover ack should be used and false + * otherwise + */ bool (*switchover_ack_needed)(void *opaque); } SaveVMHandlers; +/** + * register_savevm_live: Register a set of custom migration handlers + * + * @idstr: state section identifier + * @instance_id: instance id + * @version_id: version id supported + * @ops: SaveVMHandlers structure + * @opaque: data pointer passed to SaveVMHandlers handlers + */ int register_savevm_live(const char *idstr, uint32_t instance_id, int version_id, const SaveVMHandlers *ops, void *opaque); +/** + * unregister_savevm: Unregister custom migration handlers + * + * @obj: object associated with state section + * @idstr: state section identifier + * @opaque: data pointer passed to register_savevm_live() + */ void unregister_savevm(VMStateIf *obj, const char *idstr, void *opaque); #endif