Hi all, The first patch in this series adds a small optimization to VFIO migration by moving the STOP_COPY->STOP transition to vfio_save_cleanup(). Testing with a ConnectX-7 VFIO device showed that this can reduce downtime by up to 6%.
The rest of the series adds P2P support for VFIO migration. VFIO migration uAPI defines an optional intermediate P2P quiescent state. While in the P2P quiescent state, P2P DMA transactions cannot be initiated by the device, but the device can respond to incoming ones. Additionally, all outstanding P2P transactions are guaranteed to have been completed by the time the device enters this state. The purpose of this state is to support migration of multiple devices that are doing P2P transactions between themselves. To implement P2P migration support, all the devices must be transitioned to the P2P quiescent state before being stopped or started. This behavior is achieved by adding an optional pre VM state change callback to VMChangeStateEntry. These callbacks are invoked before the main VM state change callbacks, transitioning all the VFIO devices to the P2P state, and only then are the main callbacks invoked, which stop or start the devices. This will allow migration of multiple VFIO devices if all of them support P2P migration. Thanks. Avihai Horon (5): vfio/migration: Move from STOP_COPY to STOP in vfio_save_cleanup() sysemu: Add pre VM state change callback qdev: Add qdev_add_vm_change_state_handler_full() vfio/migration: Add P2P support for VFIO migration vfio/migration: Allow migration of multiple P2P supporting devices Joao Martins (1): vfio/migration: Refactor PRE_COPY and RUNNING state checks docs/devel/vfio-migration.rst | 93 +++++++++++++++++++------------ include/hw/vfio/vfio-common.h | 2 + include/sysemu/runstate.h | 7 +++ hw/core/vm-change-state-handler.c | 14 ++++- hw/vfio/common.c | 50 +++++++++++++---- hw/vfio/migration.c | 83 +++++++++++++++++++-------- softmmu/runstate.c | 39 +++++++++++++ hw/vfio/trace-events | 2 +- 8 files changed, 217 insertions(+), 73 deletions(-) -- 2.26.3
