[PATCH pve-qemu v2] parse-cpu-flags: stop filtering out 'pmu'

[PATCH pve-qemu v2] parse-cpu-flags: stop filtering out 'pmu'

[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 closely related to CPUID: it enables the virtual PMU, and
QEMU derives other CPUID bits from it. For example, PDCM is cleared when
it is disabled. It therefore makes sense to handle it like the other
flags, including the check for which nodes support it, rather than
exposing it as a separate property in the CPU config. Since it is a
plain boolean, it also fits the existing [+-]<flag> syntax.

Windows guests using VBS need a virtual PMU. QEMU disables it by default
and only enables it for the 'host' and 'max' models, so it is off on all
named models. Enabling it 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 and regenerate debian/recognized-CPUID-flags-x86_64.

Reported-by: David Riley <d.riley@proxmox.com>
Signed-off-by: Arthur Bied-Charreton <a.bied-charreton@proxmox.com>
---
Changes since v1 (thanks Fiona!):
* Rework commit message to explain why 'pmu' is conceptually related to
  CPU flags and not just that the syntax fits, and clarify that 'pmu' is
  disabled by default on *all* named models
* Regenerate debian/recognized-CPUID-flags-x86_64

 debian/parse-cpu-flags.pl            | 1 -
 debian/recognized-CPUID-flags-x86_64 | 1 +
 2 files changed, 1 insertion(+), 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,
diff --git a/debian/recognized-CPUID-flags-x86_64 b/debian/recognized-CPUID-flags-x86_64
index 5861e59..8b3b5ab 100644
--- a/debian/recognized-CPUID-flags-x86_64
+++ b/debian/recognized-CPUID-flags-x86_64
@@ -223,6 +223,7 @@ pks
 pku
 pmm
 pmm-en
+pmu
 pn
 pni
 popcnt
-- 
2.47.3

applied: [PATCH pve-qemu v2] parse-cpu-flags: stop filtering out 'pmu'

[Fiona Ebner]

On Tue, 13 Oct 2026 11:49:15 +0200, Arthur Bied-Charreton wrote:
> '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 closely related to CPUID: it enables the virtual PMU, and
> QEMU derives other CPUID bits from it. For example, PDCM is cleared when
> it is disabled. It therefore makes sense to handle it like the other
> flags, including the check for which nodes support it, rather than
> exposing it as a separate property in the CPU config. Since it is a
> plain boolean, it also fits the existing [+-]<flag> syntax.
> 
> [...]

Applied, thanks!

[1/1] parse-cpu-flags: stop filtering out 'pmu'
      commit: eca96893ba6db97a58924d75546673b94ab84411