It has always been possible to enable arbitrary migration capabilities and attempt to take a snapshot of the VM with the savevm/loadvm commands as well as their QMP counterparts snapshot-save/snapshot-load.
Most migration capabilities are not meant to be used with snapshots and there's a risk of crashing QEMU or producing incorrect behavior. Ideally, every migration capability would either be implemented for savevm or explicitly rejected. Add a compatibility check routine and reject the snapshot command if an incompatible capability is enabled. For now only act on the the two that actually cause a crash: multifd and mapped-ram. Resolves: https://gitlab.com/qemu-project/qemu/-/issues/2881 Signed-off-by: Fabiano Rosas <faro...@suse.de> --- migration/options.c | 26 ++++++++++++++++++++++++++ migration/options.h | 1 + migration/savevm.c | 8 ++++++++ 3 files changed, 35 insertions(+) diff --git a/migration/options.c b/migration/options.c index b0ac2ea408..8772b98dca 100644 --- a/migration/options.c +++ b/migration/options.c @@ -443,11 +443,37 @@ INITIALIZE_MIGRATE_CAPS_SET(check_caps_background_snapshot, MIGRATION_CAPABILITY_VALIDATE_UUID, MIGRATION_CAPABILITY_ZERO_COPY_SEND); +/* Snapshot compatibility check list */ +static const +INITIALIZE_MIGRATE_CAPS_SET(check_caps_savevm, + MIGRATION_CAPABILITY_MULTIFD, + MIGRATION_CAPABILITY_MAPPED_RAM, +); + static bool migrate_incoming_started(void) { return !!migration_incoming_get_current()->transport_data; } +bool migrate_can_snapshot(Error **errp) +{ + MigrationState *s = migrate_get_current(); + int i; + + for (i = 0; i < check_caps_savevm.size; i++) { + int incomp_cap = check_caps_savevm.caps[i]; + + if (s->capabilities[incomp_cap]) { + error_setg(errp, + "Snapshots are not compatible with %s", + MigrationCapability_str(incomp_cap)); + return false; + } + } + + return true; +} + /** * @migration_caps_check - check capability compatibility * diff --git a/migration/options.h b/migration/options.h index 762be4e641..20b71b6f2a 100644 --- a/migration/options.h +++ b/migration/options.h @@ -58,6 +58,7 @@ bool migrate_tls(void); /* capabilities helpers */ bool migrate_caps_check(bool *old_caps, bool *new_caps, Error **errp); +bool migrate_can_snapshot(Error **errp); /* parameters */ diff --git a/migration/savevm.c b/migration/savevm.c index ce158c3512..3be13bcfe8 100644 --- a/migration/savevm.c +++ b/migration/savevm.c @@ -3229,6 +3229,10 @@ bool save_snapshot(const char *name, bool overwrite, const char *vmstate, GLOBAL_STATE_CODE(); + if (!migrate_can_snapshot(errp)) { + return false; + } + if (migration_is_blocked(errp)) { return false; } @@ -3413,6 +3417,10 @@ bool load_snapshot(const char *name, const char *vmstate, int ret; MigrationIncomingState *mis = migration_incoming_get_current(); + if (!migrate_can_snapshot(errp)) { + return false; + } + if (!bdrv_all_can_snapshot(has_devices, devices, errp)) { return false; } -- 2.35.3
