Re: [PATCH pve-qemu] parse-cpu-flags: stop filtering out 'pmu'

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

On Tue, Oct 13, 2026 at 11:19:11AM +0200, Fiona Ebner wrote:
> Am 13.10.26 um 10:32 AM schrieb Arthur Bied-Charreton:
> > 'pmu' was excluded from the list of flags in the custom CPU flag dialog
> > because it is not a CPUID flag (not part of '-cpu help' output).
> > However, it is a plain boolean property so it fits the [+-]<flag> syntax
> > from the custom CPU config, and QEMU accepts it when set manually via
> > '+pmu'.
> 
> What I wanted to write: if it's not a CPUID flag, wouldn't it be better
> to expose it as a separate property? I.e. add to the $cpu_fmt schema and
> have a separate checkbox in the UI?
> 
> But then I looked into the implementation and the 'pmu' property is very
> closely related to the CPUID_EXT_PDCM flag, so it makes a lot of sense
> if it goes through the same "on which nodes is it supported" checks and
> if we treat it as a flag.
> 
> Could you adapt the commit message to reflect this? IMHO the argument
> with QEMU accepting the same syntax is rather weak. There has to be
> conceptual similarity too, which there is :)
> 
fair enough, will adapt the message. thanks for looking into it!
> > 
> > Windows guests using VBS need a virtual PMU, which is not enabled by
> > default on many models (EPYC-Turin, EPYC-Genoa, SapphireRapids, and
> > presumably others I have not tested). This currently requires users to
> > edit the config by hand since the flag cannot be selected in the UI.
> > 
> > Remove 'pmu' from the blacklist so it shows up in the generated flag
> > list.
> > 
> > Reported-by: David Riley <d.riley@proxmox.com>
> > Signed-off-by: Arthur Bied-Charreton <a.bied-charreton@proxmox.com>
> > ---
> >  debian/parse-cpu-flags.pl | 1 -
> >  1 file changed, 1 deletion(-)
> > 
> > diff --git a/debian/parse-cpu-flags.pl b/debian/parse-cpu-flags.pl
> > index e680f99..e1af0e8 100755
> > --- a/debian/parse-cpu-flags.pl
> > +++ b/debian/parse-cpu-flags.pl
> > @@ -66,7 +66,6 @@ my $filtered_props = {
> >          'legacy-multi-node' => 1,
> >          lmce => 1,
> >          migratable => 1,
> > -        pmu => 1,
> >          realized => 1,
> >          'start-powered-off' => 1,
> >          'tcg-cpuid' => 1,
> 
> Note: you also need to add it to debian/recognized-CPUID-flags-x86_64
I somehow completely forgot, thanks for noticing :)