Re: [pve-devel] [PATCH qemu-server] snapshot: prohibit live snapshot (remove) of qcow2 TPM drive on storage with snapshot-as-volume-chain

["Fabian Grünbichler" <f.gruenbichler@proxmox.com>]

On November 19, 2025 12:59 pm, Fiona Ebner wrote:
> QSD and swtpm currently are not prepared for dealing with
> blockdev-replace and rename operations that snapshot or snapshot
> remove operations with a snapshot-as-volume-chain storage entail.
> 
> Reported-by: Friedrich Weber <f.weber@proxmox.com>
> Signed-off-by: Fiona Ebner <f.ebner@proxmox.com>

Reviewed-by: Fabian Grünbichler <f.gruenbichler@proxmox.com>

unfortunate, but we have to live with this limitation for now..

> ---
>  src/PVE/API2/Qemu.pm | 52 ++++++++++++++++++++++++++++++++++++++++++++
>  1 file changed, 52 insertions(+)
> 
> diff --git a/src/PVE/API2/Qemu.pm b/src/PVE/API2/Qemu.pm
> index 5cdba4bb..c580bf63 100644
> --- a/src/PVE/API2/Qemu.pm
> +++ b/src/PVE/API2/Qemu.pm
> @@ -726,6 +726,36 @@ my $check_cpu_model_access = sub {
>      }
>  };
>  
> +# TODO switch to doing internal snapshots only for TPM? Need a way to tell the storage. Also needs
> +# handling for pre-existing as-volume-chain snapshots then. Or is there a way to make QSD+swtpm
> +# compatible with using volume-chain live?
> +my sub assert_tpm_snapshot_compat {
> +    my ($vmid, $conf, $op, $snap_conf) = @_;
> +
> +    return if !$conf->{tpmstate0};
> +    return if !PVE::QemuServer::Helpers::vm_running_locally($vmid);
> +
> +    my $drive = PVE::QemuServer::Drive::parse_drive('tpmstate0', $conf->{tpmstate0});
> +    my $volid = $drive->{file};
> +    my $storecfg = PVE::Storage::config();
> +
> +    if ($snap_conf) {
> +        return if !$snap_conf->{tpmstate0};
> +        my $snap_drive = PVE::QemuServer::Drive::parse_drive('tpmstate0', $snap_conf->{tpmstate0});
> +        return if $volid ne $snap_drive->{file};
> +    }
> +
> +    my $format = PVE::QemuServer::Drive::checked_volume_format($storecfg, $volid);
> +    my ($storeid) = PVE::Storage::parse_volume_id($volid, 1);
> +    if ($storeid && $format eq 'qcow2') {
> +        my $scfg = PVE::Storage::storage_config($storecfg, $storeid);
> +        if ($scfg && $scfg->{'snapshot-as-volume-chain'}) {
> +            die "snapshot $op of TPM state '$volid' on storage with 'snapshot-as-volume-chain' is"
> +                . " not yet supported while the VM is running.\n";
> +        }
> +    }
> +}
> +
>  my $cpuoptions = {
>      'cores' => 1,
>      'cpu' => 1,
> @@ -6040,6 +6070,14 @@ __PACKAGE__->register_method({
>              0);
>  
>          my $realcmd = sub {
> +            PVE::QemuConfig->lock_config(
> +                $vmid,
> +                sub {
> +                    my $conf = PVE::QemuConfig->load_config($vmid);
> +                    assert_tpm_snapshot_compat($vmid, $conf, 'create');
> +                },
> +            );
> +
>              PVE::Cluster::log_msg('info', $authuser, "snapshot VM $vmid: $snapname");
>              PVE::QemuConfig->snapshot_create(
>                  $vmid, $snapname, $param->{vmstate}, $param->{description},
> @@ -6291,6 +6329,20 @@ __PACKAGE__->register_method({
>          my $lock_obtained;
>          my $do_delete = sub {
>              $lock_obtained = 1;
> +
> +            PVE::QemuConfig->lock_config(
> +                $vmid,
> +                sub {
> +                    my $conf = PVE::QemuConfig->load_config($vmid);
> +                    assert_tpm_snapshot_compat(
> +                        $vmid,
> +                        $conf,
> +                        'delete',
> +                        $conf->{snapshots}->{$snapname},
> +                    );
> +                },
> +            );
> +
>              PVE::Cluster::log_msg('info', $authuser, "delete snapshot VM $vmid: $snapname");
>              PVE::QemuConfig->snapshot_delete($vmid, $snapname, $param->{force});
>          };
> -- 
> 2.47.3
> 
> 
> 
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> 
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