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The VFIO_MIGRATION event notifies users when a VFIO device transitions to a new state. One use case for this event is to prevent timeouts for RDMA connections to the migrated device. In this case, an external management application (not libvirt) consumes the events and disables the RDMA timeout mechanism when receiving the event for PRE_COPY_P2P state, which indicates that the device is non-responsive. This is essential because RDMA connections typically have very low timeouts (tens of milliseconds), which can be far below migration downtime. However, under heavy resource utilization, the device transition to PRE_COPY_P2P can take hundreds of milliseconds to complete. Since the VFIO_MIGRATION event is currently sent only after the transition completes, it arrives too late, after RDMA connections have already timed out. To address this, send an additional "prepare" event immediately before initiating the PRE_COPY_P2P transition. This guarantees timely event delivery regardless of how long the actual state transition takes. Signed-off-by: Avihai Horon <avihaih@nvidia.com> Acked-by: Markus Armbruster <armbru@redhat.com> Reviewed-by: Cédric Le Goater <clg@redhat.com> Link: https://lore.kernel.org/qemu-devel/20260202173406.13979-1-avihaih@nvidia.com Signed-off-by: Cédric Le Goater <clg@redhat.com>
78 lines
2.1 KiB
Python
78 lines
2.1 KiB
Python
# -*- Mode: Python -*-
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# vim: filetype=python
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#
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##
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# ************
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# VFIO devices
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# ************
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##
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##
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# @QapiVfioMigrationState:
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#
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# An enumeration of the VFIO device migration states. In addition to
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# the regular states, there are prepare states (with 'prepare' suffix)
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# which indicate that the device is just about to transition to the
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# corresponding state. Note that seeing a prepare state for state X
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# doesn't guarantee that the next state will be X, as the state
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# transition can fail and the device may transition to a different
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# state instead.
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#
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# @stop: The device is stopped.
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#
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# @running: The device is running.
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#
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# @stop-copy: The device is stopped and its internal state is
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# available for reading.
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#
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# @resuming: The device is stopped and its internal state is available
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# for writing.
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#
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# @running-p2p: The device is running in the P2P quiescent state.
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#
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# @pre-copy: The device is running, tracking its internal state and
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# its internal state is available for reading.
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#
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# @pre-copy-p2p: The device is running in the P2P quiescent state,
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# tracking its internal state and its internal state is available
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# for reading.
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#
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# @pre-copy-p2p-prepare: The device is just about to move to
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# pre-copy-p2p state. (since 11.0)
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#
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# Since: 9.1
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##
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{ 'enum': 'QapiVfioMigrationState',
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'data': [ 'stop', 'running', 'stop-copy', 'resuming', 'running-p2p',
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'pre-copy', 'pre-copy-p2p', 'pre-copy-p2p-prepare' ] }
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##
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# @VFIO_MIGRATION:
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#
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# This event is emitted when a VFIO device migration state is changed.
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#
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# @device-id: The device's id, if it has one.
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#
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# @qom-path: The device's QOM path.
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#
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# @device-state: The new changed device migration state.
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#
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# Since: 9.1
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#
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# .. qmp-example::
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#
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# <- { "timestamp": { "seconds": 1713771323, "microseconds": 212268 },
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# "event": "VFIO_MIGRATION",
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# "data": {
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# "device-id": "vfio_dev1",
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# "qom-path": "/machine/peripheral/vfio_dev1",
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# "device-state": "stop" } }
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##
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{ 'event': 'VFIO_MIGRATION',
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'data': {
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'device-id': 'str',
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'qom-path': 'str',
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'device-state': 'QapiVfioMigrationState'
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} }
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