Re: [PATCH RESEND v12 00/17] KVM: x86/pmu: Add basic support to enable guest PEBS via DS

[Like Xu]

On 19/5/2022 9:31 pm, Like Xu wrote:
> ==== Test Assertion Failure ====
>     lib/x86_64/processor.c:1207: r == nmsrs
>     pid=6702 tid=6702 errno=7 - Argument list too long
>        1    0x000000000040da11: vcpu_save_state at processor.c:1207 
> (discriminator 4)
>        2    0x00000000004024e5: main at state_test.c:209 (discriminator 6)
>        3    0x00007f9f48c2d55f: ?? ??:0
>        4    0x00007f9f48c2d60b: ?? ??:0
>        5    0x00000000004026d4: _start at ??:?
>     Unexpected result from KVM_GET_MSRS, r: 29 (failed MSR was 0x3f1)
>
> I don't think any of these failing tests care about MSR_IA32_PEBS_ENABLE
> in particular, they're just trying to do KVM_GET_MSRS/KVM_SET_MSRS.

One of the lessons I learned here is that the members of msrs_to_save_all[]
are part of the KVM ABI. We don't add feature-related MSRs until the last
step of the KVM exposure feature (in this case, adding MSR_IA32_PEBS_ENABLE,
MSR_IA32_DS_AREA, MSR_PEBS_DATA_CFG to msrs_to_save_all[] should take
effect along with exposing the CPUID bits).

Awaiting a ruling from the core guardian on this part of the git-bisect deficiency.