On Wed, Oct 23, 2024 at 02:02:12PM -0400, Peter Xu wrote: > This is a follow up of below patch from Avihai as a replacement: > > https://lore.kernel.org/qemu-devel/20241020130108.27148-3-avih...@nvidia.com/ > > This is v2 of the series, and it became a more generic rework on how we do > migration object refcounts, so I skipped a changelog because most of this > is new things. > > To put it simple, now I introduced another pointer to migration object, and > here's a simple explanation for both after all change applied (copy-paste > from one of the patch): > > /* > * We have two pointers for the global migration objects. Both of them are > * initialized early during QEMU starts, but they have different lifecycles. > * > * - current_migration > * > * This variable reflects the whole lifecycle of the migration object > * (which each QEMU can only have one). It is valid until the migration > * object is destroyed. > * > * This is the object that internal migration so far use. For example, > * internal helper migrate_get_current() references it. > * > * When all migration code can always pass over a MigrationState* around, > * this variable can logically be dropped. But we're not yet there. > * > * - global_migration > * > * This is valid only until the migration object is still valid to the > * outside-migration world (until migration_shutdown()). > * > * This should normally be always set, cleared or accessed by the main > * thread only, rather than the migration thread. > * > * All the exported functions (in include/migration) should reference the > * exported migration object only to avoid race conditions, as > * current_migration can be freed concurrently by migration thread when > * the migration thread holds the last refcount. > */ > > It allows all misc.h exported helpers to be used for the whole VM > lifecycle, so as to never crash QEMU with freed migration objects. > > Thanks, > > Peter Xu (4): > migration: Unexport dirty_bitmap_mig_init() in misc.h > migration: Reset current_migration properly > migration: Add global_migration > migration: Make all helpers in misc.h safe to use without migration > > include/migration/misc.h | 29 ++++++++---- > migration/migration.h | 4 ++ > migration/migration.c | 99 +++++++++++++++++++++++++++++++++++----- > 3 files changed, 113 insertions(+), 19 deletions(-)
Sent too soon. This breaks device-introspect-test.. Sorry. I'll look at that and repost. Meanwhile please still comment on the idea, especially when one disagrees. -- Peter Xu
