[PATCH v2] KVM: PPC: Kconfig: Enable CONFIG_VPA_PMU with KVM

[PATCH v2] KVM: PPC: Kconfig: Enable CONFIG_VPA_PMU with KVM

[Gautam Menghani]

Enable CONFIG_VPA_PMU with KVM to enable its usage. Currently, the
vpa-pmu driver cannot be used since it is not enabled in distro configs.

On fedora kernel 6.13.7, the config option is disabled:
$ cat /boot/config-6.19.12-200.fc43.ppc64le  | grep VPA_PMU
 # CONFIG_VPA_PMU is not set

Fixes: 176cda0619b6c ("powerpc/perf: Add perf interface to expose vpa counters")
Cc: stable@vger.kernel.org # v6.13+
Signed-off-by: Gautam Menghani <gautam@linux.ibm.com>
---
v1 -> v2:
1. Rebased on latest master

 arch/powerpc/kvm/Kconfig | 1 +
 1 file changed, 1 insertion(+)

diff --git a/arch/powerpc/kvm/Kconfig b/arch/powerpc/kvm/Kconfig
index 9a0d1c1aca6c..56e86b46ff13 100644
--- a/arch/powerpc/kvm/Kconfig
+++ b/arch/powerpc/kvm/Kconfig
@@ -82,6 +82,7 @@ config KVM_BOOK3S_64_HV
 	select KVM_BOOK3S_HV_POSSIBLE
 	select KVM_BOOK3S_HV_PMU
 	select CMA
+	select VPA_PMU if HV_PERF_CTRS
 	help
 	  Support running unmodified book3s_64 guest kernels in
 	  virtual machines on POWER7 and newer processors that have
-- 
2.53.0

Re: [PATCH v2] KVM: PPC: Kconfig: Enable CONFIG_VPA_PMU with KVM

[Sean Christopherson]

On Mon, May 18, 2026, Gautam Menghani wrote:
> Enable CONFIG_VPA_PMU with KVM to enable its usage. Currently, the
> vpa-pmu driver cannot be used since it is not enabled in distro configs.

That seems like a problem to take up with distros, no?

Re: [PATCH v2] KVM: PPC: Kconfig: Enable CONFIG_VPA_PMU with KVM

[Harsh Prateek Bora]

On 18/05/26 10:11 am, Gautam Menghani wrote:
> Enable CONFIG_VPA_PMU with KVM to enable its usage. Currently, the
> vpa-pmu driver cannot be used since it is not enabled in distro configs.
> 

I think the commit log needs a rephrase as irrespective of current state 
of distro configs, it makes sense to enable CONFIG_VPA_PMU for KVM 
guests on Power by default since this is the only use-case for VPA 
counters (i.e. in a KVM guest).

> On fedora kernel 6.13.7, the config option is disabled:
> $ cat /boot/config-6.19.12-200.fc43.ppc64le  | grep VPA_PMU
>   # CONFIG_VPA_PMU is not set
> 
> Fixes: 176cda0619b6c ("powerpc/perf: Add perf interface to expose vpa counters")
> Cc: stable@vger.kernel.org # v6.13+
> Signed-off-by: Gautam Menghani <gautam@linux.ibm.com>
> ---
> v1 -> v2:
> 1. Rebased on latest master
> 
>   arch/powerpc/kvm/Kconfig | 1 +
>   1 file changed, 1 insertion(+)
> 
> diff --git a/arch/powerpc/kvm/Kconfig b/arch/powerpc/kvm/Kconfig
> index 9a0d1c1aca6c..56e86b46ff13 100644
> --- a/arch/powerpc/kvm/Kconfig
> +++ b/arch/powerpc/kvm/Kconfig
> @@ -82,6 +82,7 @@ config KVM_BOOK3S_64_HV
>   	select KVM_BOOK3S_HV_POSSIBLE
>   	select KVM_BOOK3S_HV_PMU
>   	select CMA
> +	select VPA_PMU if HV_PERF_CTRS


Also, since we already select KVM_BOOK3S_HV_PMU, VPA_PMU is a natural 
extension, provided we enable only if the required dependecy is enabled.

With an update to the changelog with suggested rationale:

Reviewed-by: Harsh Prateek Bora <harshpb@linux.ibm.com>

>   	help
>   	  Support running unmodified book3s_64 guest kernels in
>   	  virtual machines on POWER7 and newer processors that have

Re: [PATCH v2] KVM: PPC: Kconfig: Enable CONFIG_VPA_PMU with KVM

[Gautam Menghani]

On Mon, May 18, 2026 at 06:01:04PM -0700, Sean Christopherson wrote:
> On Mon, May 18, 2026, Gautam Menghani wrote:
> > Enable CONFIG_VPA_PMU with KVM to enable its usage. Currently, the
> > vpa-pmu driver cannot be used since it is not enabled in distro configs.
> 
> That seems like a problem to take up with distros, no?

Rather than enabling individually for different distros, wouldn't it be
better if it is enabled with KVM automatically? I can rephrase the
commit log to emphasize that this config option is only relevant for
KVM (similar to CONFIG_KVM_BOOK3S_HV_PMU).


Thanks,
Gautam

Re: [PATCH v2] KVM: PPC: Kconfig: Enable CONFIG_VPA_PMU with KVM

[Sean Christopherson]

On Wed, May 27, 2026, Gautam Menghani wrote:
> On Mon, May 18, 2026 at 06:01:04PM -0700, Sean Christopherson wrote:
> > On Mon, May 18, 2026, Gautam Menghani wrote:
> > > Enable CONFIG_VPA_PMU with KVM to enable its usage. Currently, the
> > > vpa-pmu driver cannot be used since it is not enabled in distro configs.
> > 
> > That seems like a problem to take up with distros, no?
> 
> Rather than enabling individually for different distros, wouldn't it be
> better if it is enabled with KVM automatically? I can rephrase the
> commit log to emphasize that this config option is only relevant for
> KVM (similar to CONFIG_KVM_BOOK3S_HV_PMU).

Not if you can't turn it off.  As proposed, CONFIG_VPA_PMU gets forced to
whatever CONFIG_KVM_BOOK3S_64_HV is set to.  At that point, the existence of
the VPA_PMU Kconfig is pointless.

If you want it enabled by _default_, then turn it on by default, e.g.

diff --git arch/powerpc/platforms/pseries/Kconfig arch/powerpc/platforms/pseries/Kconfig
index f7052b131a4c..74910ce3a541 100644
--- arch/powerpc/platforms/pseries/Kconfig
+++ arch/powerpc/platforms/pseries/Kconfig
@@ -154,6 +154,7 @@ config HV_PERF_CTRS
 config VPA_PMU
        tristate "VPA PMU events"
        depends on KVM_BOOK3S_64_HV && HV_PERF_CTRS
+       default m
        help
          Enable access to the VPA PMU counters via perf. This enables
          code that support measurement for KVM on PowerVM(KoP) feature.