[pve-devel] [PATCH v4 qemu-server] Prevent starting a 32-bit VM using a 64-bit OVMF BIOS

[Filip Schauer <f.schauer@proxmox.com>]

Instead of starting a VM with a 32-bit CPU type and a 64-bit OVMF image,
throw an error before starting the VM telling the user that OVMF is not
supported on 32-bit CPU types.

To obtain a list of 32-bit CPU types, refer to builtin_x86_defs in
target/i386/cpu.c of QEMU. Exclude any entries that have the long mode
feature (CPUID_EXT2_LM).

Signed-off-by: Filip Schauer <f.schauer@proxmox.com>
---
Changes since v2:
* Simplify the check whether a 32-bit CPU type is used in combination
  with OVMF

Changes since v3:
* Move the cputypes_32bit list from QemuServer.pm to CPUConfig.pm
* Turn cputypes_32bit into a hash for lookup
* Create a helper get_cpu_bitness function in CPUConfig.pm
* Describe how the list of 32-bit CPU types was obtained

 PVE/QemuServer.pm           |  5 ++++-
 PVE/QemuServer/CPUConfig.pm | 32 ++++++++++++++++++++++++++++++++
 2 files changed, 36 insertions(+), 1 deletion(-)

diff --git a/PVE/QemuServer.pm b/PVE/QemuServer.pm
index 2063e66..5bfa11f 100644
--- a/PVE/QemuServer.pm
+++ b/PVE/QemuServer.pm
@@ -52,7 +52,7 @@ use PVE::QemuConfig;
 use PVE::QemuServer::Helpers qw(config_aware_timeout min_version windows_version);
 use PVE::QemuServer::Cloudinit;
 use PVE::QemuServer::CGroup;
-use PVE::QemuServer::CPUConfig qw(print_cpu_device get_cpu_options);
+use PVE::QemuServer::CPUConfig qw(print_cpu_device get_cpu_options get_cpu_bitness);
 use PVE::QemuServer::Drive qw(is_valid_drivename drive_is_cloudinit drive_is_cdrom drive_is_read_only parse_drive print_drive);
 use PVE::QemuServer::Machine;
 use PVE::QemuServer::Memory qw(get_current_memory);
@@ -3689,6 +3689,9 @@ sub config_to_command {
     }
 
     if ($conf->{bios} && $conf->{bios} eq 'ovmf') {
+	die "OVMF (UEFI) BIOS is not supported on 32-bit CPU types\n"
+	    if get_cpu_bitness($conf, $arch) == 32;
+
 	my ($code_drive_str, $var_drive_str) =
 	    print_ovmf_drive_commandlines($conf, $storecfg, $vmid, $arch, $q35, $version_guard);
 	push $cmd->@*, '-drive', $code_drive_str;
diff --git a/PVE/QemuServer/CPUConfig.pm b/PVE/QemuServer/CPUConfig.pm
index ca2946b..c04e749 100644
--- a/PVE/QemuServer/CPUConfig.pm
+++ b/PVE/QemuServer/CPUConfig.pm
@@ -12,6 +12,7 @@ use base qw(PVE::SectionConfig Exporter);
 our @EXPORT_OK = qw(
 print_cpu_device
 get_cpu_options
+get_cpu_bitness
 );
 
 # under certain race-conditions, this module might be loaded before pve-cluster
@@ -57,6 +58,17 @@ my $depreacated_cpu_map = {
     'Icelake-Client-noTSX' => 'Icelake-Server-noTSX',
 };
 
+my $cputypes_32bit = {
+    '486' => 1,
+    'pentium' => 1,
+    'pentium2' => 1,
+    'pentium3' => 1,
+    'coreduo' => 1,
+    'athlon' => 1,
+    'kvm32' => 1,
+    'qemu32' => 1,
+};
+
 my $cpu_vendor_list = {
     # Intel CPUs
     486 => 'GenuineIntel',
@@ -719,6 +731,26 @@ sub get_cpu_from_running_vm {
     return $1;
 }
 
+sub get_cpu_bitness {
+    my ($conf, $arch) = @_;
+
+    return if !$conf or !$arch;
+
+    if ($arch eq 'x86_64') {
+	if (my $cpu_prop_str = $conf->{cpu}) {
+	    my $cpu = PVE::JSONSchema::parse_property_string('pve-vm-cpu-conf', $cpu_prop_str)
+		or die "Cannot parse cpu description: $cpu_prop_str\n";
+
+	    my $cputype = $cpu->{cputype};
+	    return 32 if $cputypes_32bit->{$cputype};
+	}
+
+	return 64;
+    }
+
+    return 64 if ($arch eq 'aarch64');
+}
+
 __PACKAGE__->register();
 __PACKAGE__->init();
 
-- 
2.39.2