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envelope-from=peterx@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: -24 X-Spam_score: -2.5 X-Spam_bar: -- X-Spam_report: (-2.5 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.422, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_NONE=-0.0001, RCVD_IN_MSPIKE_H3=0.001, RCVD_IN_MSPIKE_WL=0.001, RCVD_IN_VALIDITY_CERTIFIED_BLOCKED=0.001, RCVD_IN_VALIDITY_RPBL_BLOCKED=0.001, SPF_HELO_PASS=-0.001, SPF_PASS=-0.001 autolearn=ham autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org queued. +Dan On Tue, Oct 07, 2025 at 03:42:13PM -0300, Fabiano Rosas wrote: > 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 > --- > migration/options.c | 27 +++++++++++++++++++++++++++ > migration/options.h | 1 + > migration/savevm.c | 8 ++++++++ > 3 files changed, 36 insertions(+) > > diff --git a/migration/options.c b/migration/options.c > index 5183112775..d9227809d7 100644 > --- a/migration/options.c > +++ b/migration/options.c > @@ -445,11 +445,38 @@ 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; > +} > + > + > bool migrate_rdma_caps_check(bool *caps, Error **errp) > { > if (caps[MIGRATION_CAPABILITY_XBZRLE]) { > diff --git a/migration/options.h b/migration/options.h > index 82d839709e..a7b3262d1e 100644 > --- a/migration/options.h > +++ b/migration/options.h > @@ -59,6 +59,7 @@ bool migrate_tls(void); > > bool migrate_rdma_caps_check(bool *caps, Error **errp); > 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 7b35ec4dd0..aafa40d779 100644 > --- a/migration/savevm.c > +++ b/migration/savevm.c > @@ -3322,6 +3322,10 @@ 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; > } > @@ -3507,6 +3511,10 @@ 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 > -- Peter Xu