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From: Jim Mattson <jmattson@google.com>
To: Yang Weijiang <weijiang.yang@intel.com>
Cc: pbonzini@redhat.com, seanjc@google.com, vkuznets@redhat.com,
	wei.w.wang@intel.com, like.xu.linux@gmail.com,
	kvm@vger.kernel.org, linux-kernel@vger.kernel.org,
	Like Xu <like.xu@linux.intel.com>
Subject: Re: [PATCH v6 04/12] KVM: vmx/pmu: Emulate MSR_ARCH_LBR_DEPTH for guest Arch LBR
Date: Fri, 16 Jul 2021 16:33:36 -0700	[thread overview]
Message-ID: <CALMp9eQR1u_iXWEg+EEtL0_4mVC_T4d_3QqWy-8a4gncN7CmHQ@mail.gmail.com> (raw)
In-Reply-To: <1626425406-18582-5-git-send-email-weijiang.yang@intel.com>

On Fri, Jul 16, 2021 at 1:36 AM Yang Weijiang <weijiang.yang@intel.com> wrote:
>
> From: Like Xu <like.xu@linux.intel.com>
>
> The number of Arch LBR entries available is determined by the value
> in host MSR_ARCH_LBR_DEPTH.DEPTH. The supported LBR depth values are
> enumerated in CPUID.(EAX=01CH, ECX=0):EAX[7:0]. For each bit "n" set
> in this field, the MSR_ARCH_LBR_DEPTH.DEPTH value of "8*(n+1)" is
> supported.
>
> On a guest write to MSR_ARCH_LBR_DEPTH, all LBR entries are reset to 0.
> KVM writes guest requested value to the native ARCH_LBR_DEPTH MSR
> (this is safe because the two values will be the same) when the Arch LBR
> records MSRs are pass-through to the guest.
>
> Signed-off-by: Like Xu <like.xu@linux.intel.com>
> Signed-off-by: Yang Weijiang <weijiang.yang@intel.com>

It might be worth noting that KVM_SET_MSRS cannot be used to emulate a
wrmsr instruction in the guest, but maybe that's already implicit.

Reviewed-by: Jim Mattson <jmattson@google.com>

  reply	other threads:[~2021-07-16 23:34 UTC|newest]

Thread overview: 15+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-07-16  8:49 [PATCH v6 00/12] Introduce Architectural LBR for vPMU Yang Weijiang
2021-07-16  8:49 ` [PATCH v6 01/12] perf/x86/intel: Fix the comment about guest LBR support on KVM Yang Weijiang
2021-07-16  8:49 ` [PATCH v6 02/12] perf/x86/lbr: Simplify the exposure check for the LBR_INFO registers Yang Weijiang
2021-07-16  8:49 ` [PATCH v6 03/12] KVM: x86: Add Arch LBR MSRs to msrs_to_save_all list Yang Weijiang
2021-07-16  8:49 ` [PATCH v6 04/12] KVM: vmx/pmu: Emulate MSR_ARCH_LBR_DEPTH for guest Arch LBR Yang Weijiang
2021-07-16 23:33   ` Jim Mattson [this message]
2021-07-19  7:27     ` Yang Weijiang
2021-07-16  8:49 ` [PATCH v6 05/12] KVM: vmx/pmu: Emulate MSR_ARCH_LBR_CTL " Yang Weijiang
2021-07-16  8:50 ` [PATCH v6 06/12] KVM: x86/pmu: Refactor code to support " Yang Weijiang
2021-07-16  8:50 ` [PATCH v6 07/12] KVM: x86: Refresh CPUID on writes to MSR_IA32_XSS Yang Weijiang
2021-07-16  8:50 ` [PATCH v6 08/12] KVM: x86: Report XSS as an MSR to be saved if there are supported features Yang Weijiang
2021-07-16  8:50 ` [PATCH v6 09/12] KVM: x86: Refine the matching and clearing logic for supported_xss Yang Weijiang
2021-07-16  8:50 ` [PATCH v6 10/12] KVM: x86: Add XSAVE Support for Architectural LBR Yang Weijiang
2021-07-16  8:50 ` [PATCH v6 11/12] KVM: x86/vmx: Check Arch LBR config when return perf capabilities Yang Weijiang
2021-07-16  8:50 ` [PATCH v6 12/12] KVM: x86/cpuid: Advise Arch LBR feature in CPUID Yang Weijiang

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