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migration: Synchronize all CPU states only for non-iterable dump

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Do one shot cpu sync at qemu_savevm_state_complete_precopy_non_iterable(),
instead of coding it separately in two places.

Note that in the context of qemu_savevm_state_complete_precopy(), this
patch is also an optimization for postcopy path, in that we can avoid sync
cpu twice during switchover: before this patch, postcopy_start() invokes
twice on qemu_savevm_state_complete_precopy(), each of them will try to
sync CPU info.  In reality, only one of them would be enough.

For background snapshot, there's no intended functional change.

Signed-off-by: Peter Xu <peterx@redhat.com>
Tested-by: Jiri Denemark <jdenemar@redhat.com>
Reviewed-by: Juraj Marcin <jmarcin@redhat.com>
Link: https://lore.kernel.org/r/20250114230746.3268797-7-peterx@redhat.com
Signed-off-by: Fabiano Rosas <farosas@suse.de>
This commit is contained in:
Peter Xu 2025-01-14 18:07:36 -05:00 committed by Fabiano Rosas
parent 4822128693
commit 89011a702f
2 changed files with 4 additions and 7 deletions
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6
migration/migration.c
View File

@ -3749,11 +3749,7 @@ static void *bg_migration_thread(void *opaque)
if (migration_stop_vm(s, RUN_STATE_PAUSED)) { if (migration_stop_vm(s, RUN_STATE_PAUSED)) {
goto fail; goto fail;
} }
/*
* Put vCPUs in sync with shadow context structures, then
* save their state to channel-buffer along with devices.
*/
cpu_synchronize_all_states();
if (qemu_savevm_state_complete_precopy_non_iterable(fb, false)) { if (qemu_savevm_state_complete_precopy_non_iterable(fb, false)) {
goto fail; goto fail;
} }

5
migration/savevm.c
View File

@ -1531,6 +1531,9 @@ int qemu_savevm_state_complete_precopy_non_iterable(QEMUFile *f,
Error *local_err = NULL; Error *local_err = NULL;
int ret; int ret;
/* Making sure cpu states are synchronized before saving non-iterable */
cpu_synchronize_all_states();
QTAILQ_FOREACH(se, &savevm_state.handlers, entry) { QTAILQ_FOREACH(se, &savevm_state.handlers, entry) {
if (se->vmsd && se->vmsd->early_setup) { if (se->vmsd && se->vmsd->early_setup) {
/* Already saved during qemu_savevm_state_setup(). */ /* Already saved during qemu_savevm_state_setup(). */
@ -1584,8 +1587,6 @@ int qemu_savevm_state_complete_precopy(QEMUFile *f, bool iterable_only)
trace_savevm_state_complete_precopy(); trace_savevm_state_complete_precopy();
cpu_synchronize_all_states();
if (!in_postcopy || iterable_only) { if (!in_postcopy || iterable_only) {
ret = qemu_savevm_state_complete_precopy_iterable(f, in_postcopy); ret = qemu_savevm_state_complete_precopy_iterable(f, in_postcopy);
if (ret) { if (ret) {