On 2026/09/28 23:54, Fabiano Rosas wrote:
Andrey Drobyshev <[email protected]> writes:
The savevm/loadvm operation doesn't make any sense in any of the CPR
modes. Saving VM state implies saving its RAM entirely, while the whole
point of CPR is avoiding that: in cpr-transfer and cpr-exec modes RAM is
preserved in place and never put into the migration stream (see
migrate_ram_is_ignored() in migration/ram.c). As a result, a snapshot
taken with such a mode set has no RAM in it, and loading a snapshot with
such a mode set fails in the RAM loader.
Currently nothing stops these operations from firing with a CPR mode
still set, e.g. after an earlier CPR attempt. Reject them early in
migrate_can_snapshot(), which guards 'savevm'/'loadvm' HMP commands as
well as 'snapshot-save'/'snapshot-load' QMP commands.
Signed-off-by: Andrey Drobyshev <[email protected]>
---
migration/options.c | 7 +++++++
1 file changed, 7 insertions(+)
diff --git a/migration/options.c b/migration/options.c
index 05b026f4bf2..f648be1302b 100644
--- a/migration/options.c
+++ b/migration/options.c
@@ -555,8 +555,15 @@ static bool migrate_incoming_started(void)
bool migrate_can_snapshot(Error **errp)
{
MigrationState *s = migrate_get_current();
+ MigMode mode = migrate_mode();
int i;
+ if (mode != MIG_MODE_NORMAL) {
+ error_setg(errp, "Snapshots are not compatible with migration mode %s",
+ MigMode_str(mode));
+ return false;
+ }
+
for (i = 0; i < check_caps_savevm.size; i++) {
int incomp_cap = check_caps_savevm.caps[i];
+CC Akihiko Odaki
Reviewed-by: Fabiano Rosas <[email protected]>
Thanks for CCing me. This is also relevant to my recent work on Xen
migration. The snapshot RAM-saving path does not support Xen's memory
mappings, so migrate_can_snapshot() should reject Xen as well.
If you send another revision, could you include that check? This is a
pre-existing issue, though, so it need not hold up this patch.
Reviewed-by: Akihiko Odaki <[email protected]>
Regards,
Akihiko Odaki
