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

[Filip Schauer]

Patch v5 is available:

https://lists.proxmox.com/pipermail/pve-devel/2023-December/061079.html

On 13/12/2023 17:53, Filip Schauer wrote:
> 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 at 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();
>