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

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Date:   Thu, 19 May 2022 21:31:46 +0800
From:   Like Xu <like.xu.linux@...il.com>
To:     Vitaly Kuznetsov <vkuznets@...hat.com>
Cc:     Peter Zijlstra <peterz@...radead.org>,
        Sean Christopherson <seanjc@...gle.com>,
        Wanpeng Li <wanpengli@...cent.com>,
        Joerg Roedel <joro@...tes.org>, linux-kernel@...r.kernel.org,
        kvm@...r.kernel.org, Paolo Bonzini <pbonzini@...hat.com>,
        Jim Mattson <jmattson@...gle.com>
Subject: Re: [PATCH RESEND v12 00/17] KVM: x86/pmu: Add basic support to
 enable guest PEBS via DS

On 19/5/2022 8:14 pm, Vitaly Kuznetsov wrote:
> Like Xu <like.xu.linux@...il.com> writes:
> 
> ...
> 
> Hi, the following commit
> 
>>    KVM: x86/pmu: Add IA32_PEBS_ENABLE MSR emulation for extended PEBS
> 
> (currently in kvm/queue) breaks a number of selftests, e.g.:

Indeed, e.g.:

x86_64/hyperv_clock
x86_64/max_vcpuid_cap_test
x86_64/mmu_role_test

> 
> # ./tools/testing/selftests/kvm/x86_64/state_test

This test continues to be silent after the top commit a3808d884612 ("KVM: x86/pmu:
Expose CPUIDs feature bits PDCM, DS, DTES64"), which implies a root cause.

Anyway, thanks for this git-bisect report.

> ==== 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.
>