[PATCH v2 3/4] KVM: arm64: Pass pmu events to hyp via vcpu

[Fuad Tabba]

Hi Marc,


On Mon, May 9, 2022 at 11:41 AM Marc Zyngier <maz at kernel.org> wrote:
>
> On Mon, 09 May 2022 10:54:59 +0100,
> Fuad Tabba <tabba at google.com> wrote:
> >
> > Instead of the host accessing hyp data directly, pass the pmu
> > events of the current cpu to hyp via the vcpu.
> >
> > This adds 64 bits (in two fields) to the vcpu that need to be
> > synced before every vcpu run in nvhe and protected modes.
> > However, it isolates the hypervisor from the host, which allows
> > us to use pmu in protected mode in a subsequent patch.
> >
> > No functional change intended.
>
> BTW, there *are* plenty of functional changes, even if there was no
> issue with the patch. The lifetime of the data structure changes, its
> sharing changes, and its memory footprint is different.
>
> I guess what you are trying to say is that there shouldn't be any
> visible side effect of this patch. But I don't think these are the
> same things.

Always thought that in this context functional == functionality. Will
make it clearer in the next commit message that there should be no
visible side effect changes instead.

Thanks,
/fuad
>
> Thanks,
>
>         M.
>
> --
> Without deviation from the norm, progress is not possible.