[PATCH qemu-server 1/3] cpu flags: include Hyper-V enlightenment flags in supported flags

[Arthur Bied-Charreton <a.bied-charreton@proxmox.com>]

QEMU advertises the Hyper-V enlightenment flags [0] through a different
CPUID range, which query-cpu-model-expansion does not cover by default.

This leads to query_supported_cpu_flags reporting the hv-* flags as
unsupported [1] even though some of them are in the VM-specific flags
and QEMU would accept them when starting a VM.

Enable hv-passthrough in the temporary VM used to query supported flags
for KVM, making it advertise support for the hv-* flags as well.

[0] https://www.qemu.org/docs/master/system/i386/hyperv.html
[1] https://forum.proxmox.com/threads/incorrect-supported-cpu-flags.183722/#post-853902

Signed-off-by: Arthur Bied-Charreton <a.bied-charreton@proxmox.com>
---
 src/PVE/QemuServer.pm | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/src/PVE/QemuServer.pm b/src/PVE/QemuServer.pm
index 118f26bc..239b0cab 100644
--- a/src/PVE/QemuServer.pm
+++ b/src/PVE/QemuServer.pm
@@ -2982,12 +2982,15 @@ sub query_supported_cpu_flags {
         my $rc = run_command($cmd, noerr => 1, quiet => 0);
         die "QEMU flag querying VM exited with code " . $rc if $rc;
 
+        my $model = { name => $kvm ? 'host' : 'max' };
+        $model->{props} = { 'hv-passthrough' => JSON::true } if $kvm;
+
         eval {
             my $cmd_result = mon_cmd(
                 $fakevmid,
                 'query-cpu-model-expansion',
                 type => 'full',
-                model => { name => $kvm ? 'host' : 'max' },
+                model => $model,
             );
 
             my $props = $cmd_result->{model}->{props};
-- 
2.47.3