[libvirt] [PATCH v2 1/3] qemu: Warn of restore with managed save being risky

Internal snapshots of a non-running domain do not carry any memory state and restoring such a snapshot will not replace existing saved memory state. This allows a scenario, where a user first suspends a domain into managedsave, restores a non-running snapshot and then resumes the domain from managedsave. After that, the guest system will run with its previous memory state atop a different disk state. The most obvious possible fallout from this is extensive file system corruption. Swap content and RAID bitmaps might also be off. This has been discussed[1] and fixed[2] from the end-user perspective for virt-manager. This patch marks the restore operation as risky at the libvirt level, requiring the user to remove the saved memory state first or force the operation. [1] https://www.redhat.com/archives/virt-tools-list/2019-November/msg00011.html [2] https://www.redhat.com/archives/virt-tools-list/2019-December/msg00049.html Signed-off-by: Michael Weiser <michael.weiser(a)gmx.de&gt; Reviewed-by: Daniel Henrique Barboza <danielhb413(a)gmail.com&gt; Cc: Cole Robinson <crobinso(a)redhat.com&gt; --- src/qemu/qemu_driver.c | 9 +++++++++ 1 file changed, 9 insertions(+) diff --git a/src/qemu/qemu_driver.c b/src/qemu/qemu_driver.c index ec8faf384c..691a9b45c7 100644 --- a/src/qemu/qemu_driver.c +++ b/src/qemu/qemu_driver.c @@ -16652,6 +16652,15 @@ qemuDomainRevertToSnapshot(virDomainSnapshotPtr snapshot, _("must respawn qemu to start inactive snapshot")); goto endjob; } + if (vm->hasManagedSave && + !(snapdef->state == VIR_DOMAIN_SNAPSHOT_RUNNING || + snapdef->state == VIR_DOMAIN_SNAPSHOT_PAUSED)) { + virReportError(VIR_ERR_SNAPSHOT_REVERT_RISKY, "%s", + _("snapshot without memory state, removal of " + "existing managed saved state strongly " + "recommended to avoid corruption")); + goto endjob; + } } if (snap->def->dom) { -- 2.24.1