[PATCH 0/7] KVM: arm64: PMU: Allow userspace to limit the number of PMCs on vCPU

[Reiji Watanabe]

Hi Jonathan,

On Tue, Jan 3, 2023 at 4:47 AM Marc Zyngier <maz at kernel.org> wrote:
>
> On Tue, 03 Jan 2023 12:40:34 +0000,
> Jonathan Cameron <Jonathan.Cameron at Huawei.com> wrote:
> >
> > On Thu, 29 Dec 2022 19:59:21 -0800
> > Reiji Watanabe <reijiw at google.com> wrote:
> >
> > > The goal of this series is to allow userspace to limit the number
> > > of PMU event counters on the vCPU.
> >
> > Hi Rieji,
> >
> > Why do you want to do this?
> >
> > I can conjecture a bunch of possible reasons, but they may not
> > match up with your use case. It would be useful to have that information
> > in the cover letter.
>
> The most obvious use case is to support migration across systems that
> implement different numbers of counters. Similar reasoning could also
> apply to the debug infrastructure (watchpoints, breakpoints).

Exactly, this is to unblock migration support between systems
that implement different numbers of counters.
I will include this information in the cover letter when I update
the series for the v2.

Thanks,
Reiji



>
> In any case, being able to decouple the VM from the underlying HW
> within the extent that the architecture permits it seems like a
> valuable goal.
>
> Thanks,
>
>         M.
>
> --
> Without deviation from the norm, progress is not possible.