I started looking at this problem as a whole when reviewing Fabiano's series, especially the patch (for a QEMU crash [1]):
https://lore.kernel.org/r/20241125144612.16194-5-faro...@suse.de The proposed patch could work, but it's unwanted to add such side effect to migration. So I start to think about whether we can provide a cleaner approach, at least remove that "we must active the disk for migration" dependency, because migration really don't need the disks to be active.. It's also a pure wish that, if bdrv_inactivate_all() could be benign to be called even if all disks are already inactive. Then problem also gone. After all, similar call on bdrv_activate_all() upon all-active disks is all fine. I hope that wish could still be fair. And when I was looking at that, I found more things spread all over the place on disk activation. I decided to clean all of them up, while hopefully fixing the QEMU crash [1] too. So this is what I came up with as of today. Marking RFC as of now, just to collect some feedbacks first. At least I'd like to go with one more patch to deprecate late-block-active - not deprecating its function, but make it always happen (which is the default as of now for Libvirt), which should hopefully be migration-ABI-safe. With the help of Fabiano's test cases, I at least am sure this series works for the ping pong migrations, and all existing qtests. Let me know, thanks. [1] https://gitlab.com/qemu-project/qemu/-/issues/2395 Fabiano Rosas (4): tests/qtest/migration: Move more code under only_target tests/qtest/migration: Don't use hardcoded strings for -serial tests/qtest/migration: Support cleaning up only one side of migration tests/qtest/migration: Test successive migrations Peter Xu (7): migration: Add helper to get target runstate migration/block: Make late-block-active the default migration/block: Apply late-block-active behavior to postcopy migration/block: Fix possible race with block_inactive migration/block: Merge block reactivations for fail/cancel migration/block: Extend the migration_block_* API to dest side migration/block: Apply the migration_block_* API to postcopy migration/migration.h | 33 ++++- tests/qtest/migration-helpers.h | 2 + migration/migration.c | 177 +++++++++++----------- migration/savevm.c | 32 ++-- tests/qtest/migration-helpers.c | 8 + tests/qtest/migration-test.c | 252 +++++++++++++++++++++++++------- 6 files changed, 344 insertions(+), 160 deletions(-) -- 2.47.0
