Re: [PATCH v7 03/12] KVM: arm64: PMU: Clear PM{C,I}NTEN{SET,CLR} and PMOVS{SET,CLR} on vCPU reset

[Oliver Upton <oliver.upton@linux.dev>]

Hi Raghu,

Can you please make sure you include leading and trailing whitespace for
your inline replies? The message gets extremely dense and is difficult
to read.

Also -- delete any unrelated context from your replies. If there's a
localized conversation about a particular detail there's no reason to
keep the entire thread in the body.

On Thu, Oct 19, 2023 at 11:46:22AM -0700, Raghavendra Rao Ananta wrote:
> On Wed, Oct 18, 2023 at 2:16 PM Raghavendra Rao Ananta
> <rananta@google.com> wrote:
> > I had a brief discussion about this with Oliver, and it looks like we
> > might need a couple of additional changes for these register accesses:
> > - For the userspace accesses, we have to implement explicit get_user
> > and set_user callbacks that to filter out the unimplemented counters
> > using kvm_pmu_valid_counter_mask().
> Re-thinking the first case: Since these registers go through a reset
> (reset_pmu_reg()) during initialization, where the valid counter mask
> is applied, and since we are sanitizing the registers with the mask
> before running the guest (below case), will implementing the
> {get,set}_user() add any value, apart from just keeping userspace in
> sync with every update of PMCR.N?

KVM's sysreg emulation (as seen from userspace) fails to uphold the RES0
bits of these registers. That's a bug.

-- 
Thanks,
Oliver