[pve-devel] [PATCH qemu-server 4/7] cpu config: introduce vendor-agnostic 'nested-virt' CPU flag

[Daniel Kral]

On Fri Oct 31, 2025 at 1:27 PM CET, Fiona Ebner wrote:
> @@ -578,8 +588,34 @@ sub print_cpu_device {
>  sub resolve_cpu_flags {
>      my $flags = {};
>  
> +    my $nested_flag;
> +    my $nested_flag_resolved;
> +    my $resolve_nested_flag = sub {
> +        if (!$nested_flag_resolved) {
> +            my $host_cpu_flags = PVE::ProcFSTools::read_cpuinfo()->{flags};
> +            if ($host_cpu_flags =~ m/\s(svm|vmx)\s/) {
> +                $nested_flag = $1;
> +            } else {
> +                log_warn("ignoring 'nested-virt' CPU flag - unable to resolve from host CPU flags");
> +            }
> +            $nested_flag_resolved = 1;
> +        }
> +        return $nested_flag;
> +    };
> +
>      for my $hash (@_) {

nit: maybe now's a good time to give @_ a name with the $nested_flag bit
     in between? But I can see the naming collision with $flags..

>          for my $flag_name (keys %$hash) {
> +            if ($flag_name eq 'nested-virt') {
> +                my $nested_flag_name = $resolve_nested_flag->() or next;
> +                if ($hash->{$nested_flag_name}) {
> +                    warn "warning: CPU flag '$flag_name' overrides '$nested_flag_name'\n";
> +                } else {
> +                    print "CPU flag '$flag_name' resolved to '$nested_flag_name'\n";
> +                }
> +                $hash->{$nested_flag_name} = delete($hash->{$flag_name});
> +                $flag_name = $nested_flag_name;
> +            }
> +
>              my $flag = $hash->{$flag_name};
>              my $old_flag = $flags->{$flag_name};
>