[PATCH qemu-server 1/5] drive: improve and extend TPM drive size helpers

[Thomas Ellmenreich <t.ellmenreich@proxmox.com>]

The size of a created TPM drive is always based on a constant of 4 MiB, but
if the backing storage has a larger granularity than this, the TPM silently
ignores it. Account for this properly.

Adjust the 'update_tpmstate_size' subroutine so that it checks for the
actual TPM drive size, but falls back on the constant to ensure a
minimum size of 4MiB.

Introduce a new 'get_tpmstate_size' subroutine that only determines
the current best size and returns it as bytes.

Suggested-by: Fiona Ebner <f.ebner@proxmox.com>
Signed-off-by: Thomas Ellmenreich <t.ellmenreich@proxmox.com>
---
 src/PVE/QemuMigrate.pm |  7 ++++---
 src/PVE/QemuServer.pm  | 25 +++++++++++++++++++++++--
 2 files changed, 27 insertions(+), 5 deletions(-)

diff --git a/src/PVE/QemuMigrate.pm b/src/PVE/QemuMigrate.pm
index 6605f5d8..3845fb41 100644
--- a/src/PVE/QemuMigrate.pm
+++ b/src/PVE/QemuMigrate.pm
@@ -685,10 +685,11 @@ sub config_update_local_disksizes {
         PVE::QemuServer::update_efidisk_size($conf);
     }
 
-    # TPM state might have an irregular filesize, to avoid problems on transfer
-    # we always assume the static size of 4M to allocate on the target
+    # TPM state might have an irregular file size, or have increased
+    # significantly due to differences in granularity. To avoid problems on
+    # transfer, update the TPM disk size.
     if (defined($conf->{tpmstate0})) {
-        PVE::QemuServer::update_tpmstate_size($conf);
+        PVE::QemuServer::update_tpmstate_size($conf, $self->{storecfg});
     }
 }
 
diff --git a/src/PVE/QemuServer.pm b/src/PVE/QemuServer.pm
index 135c993f..89192e9f 100644
--- a/src/PVE/QemuServer.pm
+++ b/src/PVE/QemuServer.pm
@@ -7972,14 +7972,35 @@ sub update_efidisk_size {
     return;
 }
 
+# Takes a VM config and the storage configuration. Parses the configuration,
+# checks the drive size and updates it to a more up to date value and finally
+# writes the new size back into the provided config.
 sub update_tpmstate_size {
-    my ($conf) = @_;
+    my ($conf, $storecfg) = @_;
+    return if !defined($conf) || !defined($storecfg) || !defined($conf->{tpmstate0});
 
     my $disk = PVE::QemuServer::parse_drive('tpmstate0', $conf->{tpmstate0});
-    $disk->{size} = PVE::QemuServer::Drive::TPMSTATE_DISK_SIZE;
+
+    $disk->{size} = get_tpmstate_size($disk->{file}, $storecfg);
     $conf->{tpmstate0} = print_drive($disk);
 }
 
+# Takes in a volume id and the storage configuration. Will then try to find
+# the actual storage size of the TPM drive.
+sub get_tpmstate_size {
+    my ($volid, $storecfg) = @_;
+
+    return if !defined($volid) || !defined($storecfg);
+
+    my $size = eval { PVE::Storage::volume_size_info($storecfg, $volid, 10) };
+
+    if (!$size || $size < PVE::QemuServer::Drive::TPMSTATE_DISK_SIZE) {
+        $size = PVE::QemuServer::Drive::TPMSTATE_DISK_SIZE;
+    }
+
+    return $size;
+}
+
 sub vm_iothreads_list {
     my ($vmid) = @_;
 
-- 
2.47.3