commit ff180c6bd7a8fad48099b767ad5e8340cec4fb87
author Avihai Horon <avihaih@nvidia.com> Mon Apr 03 16:00:00 2023 +0300
committer Alex Williamson <alex.williamson@redhat.com> Tue May 09 09:30:13 2023 -0600
tree 880d20e1d05ad3c5b6b63b5898a147dcad237fa6
parent 2dca1b37a7605abb135559ef1b0d63929e7ae60d

vfio/migration: Skip log_sync during migration SETUP state

Currently, VFIO log_sync can be issued while migration is in SETUP
state. However, doing this log_sync is at best redundant and at worst
can fail.

Redundant -- all RAM is marked dirty in migration SETUP state and is
transferred only after migration is set to ACTIVE state, so doing
log_sync during migration SETUP is pointless.

Can fail -- there is a time window, between setting migration state to
SETUP and starting dirty tracking by RAM save_live_setup handler, during
which dirty tracking is still not started. Any VFIO log_sync call that
is issued during this time window will fail. For example, this error can
be triggered by migrating a VM when a GUI is active, which constantly
calls log_sync.

Fix it by skipping VFIO log_sync while migration is in SETUP state.

Fixes: 758b96b61d5c ("vfio/migrate: Move switch of dirty tracking into vfio_memory_listener")
Signed-off-by: Avihai Horon <avihaih@nvidia.com>
Link: https://lore.kernel.org/r/20230403130000.6422-1-avihaih@nvidia.com
Signed-off-by: Alex Williamson <alex.williamson@redhat.com>