qemu/qemu.git/migration/multifd-device-state.c, branch master

migration: Replace migrate_set_error() with migrate_error_propagate()

2025-12-23T14:24:34+00:00

migrate_set_error() currently doesn't take ownership of the error being passed in. It's not aligned with the error API and meanwhile it also makes most of the caller free the error explicitly. Change the API to take the ownership of the Error object instead. This should save a lot of error_copy() invocations. Reviewed-by: Markus Armbruster Link: https://lore.kernel.org/r/20251201194510.1121221-8-peterx@redhat.com [peterx: break line for qemu_savevm_send_packaged, per markus] Signed-off-by: Peter Xu

migration: Use explicit error_free() instead of g_autoptr

2025-12-23T14:24:34+00:00

There're only two use cases of g_autoptr to free Error objects in migration code paths. Due to the nature of how Error should be used (normally ownership will be passed over to Error APIs, like error_report_err), auto-free functions may be error prone on its own. The auto cleanup function was merged without proper review, as pointed out by Dan and Markus: https://lore.kernel.org/r/aSWSLMi6ZhTCS_p2@redhat.com Remove the two use cases so that we can remove the auto cleanup function, hence suggest to not use auto frees for Errors. Suggested-by: Markus Armbruster Reviewed-by: Markus Armbruster Link: https://lore.kernel.org/r/20251201194510.1121221-2-peterx@redhat.com Signed-off-by: Peter Xu

migration: Rename save_live_complete_precopy_thread to save_complete_precopy_thread

2025-07-11T13:37:39+00:00

Recent patch [1] renames the save_live_complete_precopy handler to save_complete, as the machine is not live in most cases when this handler is executed. The same is true also for save_live_complete_precopy_thread, therefore this patch removes the "live" keyword from the handler itself and related types to keep the naming unified. In contrast to save_complete, this handler is only executed at the end of precopy, therefore the "precopy" keyword is retained. [1]: https://lore.kernel.org/all/20250613140801.474264-7-peterx@redhat.com/ Cc: Alex Williamson Cc: Cédric Le Goater Signed-off-by: Juraj Marcin Link: https://lore.kernel.org/r/20250626085235.294690-1-jmarcin@redhat.com Signed-off-by: Peter Xu Signed-off-by: Fabiano Rosas

migration: Add save_live_complete_precopy_thread handler

2025-03-06T05:47:33+00:00

This SaveVMHandler helps device provide its own asynchronous transmission of the remaining data at the end of a precopy phase via multifd channels, in parallel with the transfer done by save_live_complete_precopy handlers. These threads are launched only when multifd device state transfer is supported. Management of these threads in done in the multifd migration code, wrapping them in the generic thread pool. Signed-off-by: Maciej S. Szmigiero Reviewed-by: Peter Xu Link: https://lore.kernel.org/qemu-devel/eac74a4ca7edd8968bbf72aa07b9041c76364a16.1741124640.git.maciej.szmigiero@oracle.com Signed-off-by: Cédric Le Goater

migration/multifd: Add multifd_device_state_supported()

2025-03-06T05:47:33+00:00

Since device state transfer via multifd channels requires multifd channels with packets and is currently not compatible with multifd compression add an appropriate query function so device can learn whether it can actually make use of it. Reviewed-by: Fabiano Rosas Reviewed-by: Peter Xu Signed-off-by: Maciej S. Szmigiero Link: https://lore.kernel.org/qemu-devel/1ff0d98b85f470e5a33687406e877583b8fab74e.1741124640.git.maciej.szmigiero@oracle.com Signed-off-by: Cédric Le Goater

migration/multifd: Make MultiFDSendData a struct

2025-03-06T05:47:33+00:00

The newly introduced device state buffer can be used for either storing VFIO's read() raw data, but already also possible to store generic device states. After noticing that device states may not easily provide a max buffer size (also the fact that RAM MultiFDPages_t after all also want to have flexibility on managing offset[] array), it may not be a good idea to stick with union on MultiFDSendData.. as it won't play well with such flexibility. Switch MultiFDSendData to a struct. It won't consume a lot more space in reality, after all the real buffers were already dynamically allocated, so it's so far only about the two structs (pages, device_state) that will be duplicated, but they're small. With this, we can remove the pretty hard to understand alloc size logic. Because now we can allocate offset[] together with the SendData, and properly free it when the SendData is freed. [MSS: Make sure to clear possible device state payload before freeing MultiFDSendData, remove placeholders for other patches not included] Signed-off-by: Peter Xu Signed-off-by: Maciej S. Szmigiero Acked-by: Fabiano Rosas Link: https://lore.kernel.org/qemu-devel/7b02baba8e6ddb23ef7c349d312b9b631db09d7e.1741124640.git.maciej.szmigiero@oracle.com Signed-off-by: Cédric Le Goater

migration/multifd: Device state transfer support - send side

2025-03-06T05:47:33+00:00

A new function multifd_queue_device_state() is provided for device to queue its state for transmission via a multifd channel. Reviewed-by: Peter Xu Signed-off-by: Maciej S. Szmigiero Link: https://lore.kernel.org/qemu-devel/ebd55768d3e5fecb5eb3f197bad9c0c07e5bc084.1741124640.git.maciej.szmigiero@oracle.com Signed-off-by: Cédric Le Goater