On 03/23/17 10:29, Peter Krempa wrote:
> If the variable store (<nvram>) file is raw qemu can't do a snapshot of
> it and thus the snapshot would be incomplete. QEMU does no reject such
> snapshot.
>
> 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.
> ---
>
> Notes:
> v2:
> - changed error code to OPERATION_UNSUPPORTED (from CONFIG_UNSUPPORTED)
> - dropped mention of QEMU from the error message
> - dropped mentions of OVMF or the firmware itself altoghether, the culprit is
> the pflash device regardless of the software it contains
> - mentioned all the stuff in the commit message and comment
>
> We also will need to introduce a way to snapshot the pflash for external
> snapshots which is currently impossible as well, but fortunately does not
> have inherent drawbacks as internal snapshots.
>
> src/qemu/qemu_driver.c | 10 ++++++++++
> 1 file changed, 10 insertions(+)
>
> diff --git a/src/qemu/qemu_driver.c b/src/qemu/qemu_driver.c
> index 676295208..202d190b3 100644
> --- a/src/qemu/qemu_driver.c
> +++ b/src/qemu/qemu_driver.c
> @@ -13873,6 +13873,16 @@ qemuDomainSnapshotPrepare(virConnectPtr conn,
> goto cleanup;
> }
>
> + /* Internal snapshots don't work with VMs with OVMF loader since qemu does
> + * not snapshot the variable store */
> + 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;
>
Reviewed-by: Laszlo Ersek <lersek@xxxxxxxxxx>
Thanks!
Laszlo
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