Re: [PATCH v3 1/3] arm: perf: Include threshold control fields valid in PMEVTYPER mask

[Oliver Upton]

Hi James,

On Tue, Oct 10, 2023 at 03:15:41PM +0100, James Clark wrote:
> FEAT_PMUv3_TH (Armv8.8) adds two new fields to PMEVTYPER, so include
> them in the mask. These aren't writable on 32 bit kernels as they are in
> the high part of the register, so split the mask definition to the asm
> files for each platform.
> 
> Now where the value is used in some parts of KVM, include the asm file.
> There is no impact on guest PMUs emulated with KVM because the new
> fields are ignored when constructing the attributes for opening the
> event. But if threshold support is added to KVM at a later time no
> change to the mask will be needed.

KVM should treat TH and TC as RES0 if the feature isn't virtualized. I'd
rather move KVM away from using ARMV8_PMU_EVTYPE_MASK in the first
place. Looks like we already have an issue with the NSH bit, so I've
sent the below patch to fix it.

https://lore.kernel.org/kvmarm/20231011081649.3226792-3-oliver.upton@xxxxxxxxx/

-- 
Thanks,
Oliver