From 9e2465834f4bff4068e270f15e9ed5d7301de045 Mon Sep 17 00:00:00 2001
From: Peter Krempa <pkrempa@redhat.com>
Date: Wed, 1 Mar 2017 09:15:33 +0100
Subject: [PATCH] qemu: snapshot: Forbid internal snapshots with pflash
firmware
If the variable store (<nvram>) file is raw qemu can't do a snapshot of
it and thus the snapshot fails. QEMU rejects such snapshot by a message
which would not be properly interpreted as an error by libvirt.
Additionally allowing to use a qcow2 variable store backing file would
solve this issue but then it would become eligible to become target of
the memory dump.
Offline internal snapshot would be incomplete too with either storage
format since libvirt does not handle the pflash file in this case.
Forbid such snapshot so that we can avoid problems.
---
src/qemu/qemu_driver.c | 16 ++++++++++++++++
1 file changed, 16 insertions(+)
diff --git a/src/qemu/qemu_driver.c b/src/qemu/qemu_driver.c
index 6762952080..4aba981a85 100644
--- a/src/qemu/qemu_driver.c
+++ b/src/qemu/qemu_driver.c
@@ -13873,6 +13873,22 @@ qemuDomainSnapshotPrepare(virConnectPtr conn,
goto cleanup;
}
+ /* internal snapshots + pflash based loader have the following problems:
+ * - if the variable store is raw, the snapshot fails
+ * - alowing a qcow2 image as the varstore would make it eligible to receive
+ * the vmstate dump, which would make it huge
+ * - offline snapshot would not snapshot the varstore at all
+ *
+ * Avoid the issues by forbidding internal snapshot with pflash completely.
+ */
+ if (found_internal &&
+ vm->def->os.loader->type == VIR_DOMAIN_LOADER_TYPE_PFLASH) {
+ virReportError(VIR_ERR_OPERATION_UNSUPPORTED, "%s",
+ _("internal snapshots of a VM with pflash based "
+ "firmware are not supported"));
+ goto cleanup;
+ }
+
/* Alter flags to let later users know what we learned. */
if (external && !active)
*flags |= VIR_DOMAIN_SNAPSHOT_CREATE_DISK_ONLY;