Re: [PATCH 00/18] KVM: arm64: Support FEAT_PMUv3 on Apple hardware

[Will Deacon]

Hi Oliver,

On Tue, Dec 17, 2024 at 01:20:30PM -0800, Oliver Upton wrote:
> One of the interesting features of some Apple M* parts is an IMPDEF trap
> that routes EL1/EL0 accesses of the PMUv3 registers to EL2. This allows
> a hypervisor to emulate an architectural PMUv3 on top of the IMPDEF PMU
> hardware present in the CPU.
> 
> And if you squint, this _might_ look like a CPU erratum :-)
> 
> This series takes advantage of these IMPDEF traps to provide PMUv3 to
> KVM guests. As a starting point, only expose the fixed CPU cycle counter
> and no event counters. Conveniently, this is enough to get Windows
> running as a KVM guest on Apple hardware.
> 
> I've tried to keep the deviation to a minimum by refactoring some of the
> flows used for PMUv3, e.g. computing PMCEID from the arm_pmu bitmap
> instead of reading hardware directly.

What's your plan for this series? I started looking at it and I can take
the first four apple_m1 patches if you like?

Will