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Date:   Tue, 16 May 2023 21:29:07 +0800
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Subject: Re: [PATCH 0/2] KVM support for Intel PMU v5 fixed function PMC
 bitmap
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To:     Anselm Busse <abusse@amazon.com>
Cc:     dwmw@amazon.co.uk, hborghor@amazon.de, sironi@amazon.de,
        Sean Christopherson <seanjc@google.com>,
        Paolo Bonzini <pbonzini@redhat.com>,
        Thomas Gleixner <tglx@linutronix.de>,
        Ingo Molnar <mingo@redhat.com>, Borislav Petkov <bp@alien8.de>,
        Dave Hansen <dave.hansen@linux.intel.com>, x86@kernel.org,
        "H. Peter Anvin" <hpa@zytor.com>, kvm@vger.kernel.org,
        linux-kernel@vger.kernel.org
References: <20230427095333.35038-1-abusse@amazon.com>
From:   Like Xu <like.xu.linux@gmail.com>
In-Reply-To: <20230427095333.35038-1-abusse@amazon.com>
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On 27/4/2023 5:53 pm, Anselm Busse wrote:
> Starting with v5, the Intel PMU allows to indicate the available fixed
> function PMCs not only through CPUID.0AH.EDX[4:0] but also through a
> bit mask in CPUID.0AH.ECX. According to the SDM the OS can consider a
> fix function PMC i supported for:
> 
> CPUID.0AH.ECX[i] || (CPUID.0AH.EDX[4:0] > i)

Yes, this feature is attractive for virtualization scenarios, and it gives 
flexibility
to control which fixed counters are available or not in the virtual machine.

However, currently KVM/x86 also supports Intel PMU V2, so I would expect
that we will review the enablement code for v3 and v4 first.

Ref: 
https://lore.kernel.org/kvm/CALMp9eQVnk8gkOpX5AHhaCr8-5Fe=qNuX8PUP1Gv2H5FSYmHSw@mail.gmail.com/

> 
> This behavior is already supported by the Intel PMU driver. However, KVM
> support is missing. This patch series add the support by first
> refactoring the tracking of available fixed function PMCs in KVM from a
> number to a bitmap in the frist patch. The second patch populates the
> bitmap accoring to the rule given by the SDM mentioned above.
> 
> Regards,
> Anselm
> 
> Anselm Busse (2):
>    KVM: vmx/pmu: Indicate available fixed function PMCs through a bitmap
>    KVM: vmx/pmu: Add support for selected fixed vPMU enablement for PMU v5
> 
>   arch/x86/include/asm/kvm_host.h |  2 +-
>   arch/x86/kvm/pmu.h              |  6 ++---
>   arch/x86/kvm/svm/pmu.c          |  2 +-
>   arch/x86/kvm/vmx/pmu_intel.c    | 40 ++++++++++++++++++++-------------
>   4 files changed, 30 insertions(+), 20 deletions(-)
> 
> 
> base-commit: 0cfd8703e7da687924371e9bc77a025bdeba9637