linux-kernel - Re: [RESEND PATCH v4 00/10] KVM: x86/pmu: Guest Architectural LBR Enabling

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Message-ID: <1183cac7-eab9-d3ab-99bc-5f1fa0a552a8@gmail.com>
Date:   Wed, 23 Jun 2021 21:32:06 +0800
From:   Like Xu <like.xu.linux@...il.com>
To:     pbonzini@...hat.com, Sean Christopherson <seanjc@...gle.com>
Cc:     Vitaly Kuznetsov <vkuznets@...hat.com>,
        Wanpeng Li <wanpengli@...cent.com>,
        Jim Mattson <jmattson@...gle.com>,
        Joerg Roedel <joro@...tes.org>, wei.w.wang@...el.com,
        kvm@...r.kernel.org, linux-kernel@...r.kernel.org,
        Yang Weijiang <weijiang.yang@...el.com>
Subject: Re: [RESEND PATCH v4 00/10] KVM: x86/pmu: Guest Architectural LBR
 Enabling

Hi Paolo,

It looks that we don't have perf subsystem dependency
to enable guest Arch LBR here and it also has tests to cover it.

Do you have any concerns about not accepting them ?

Thanks,
Like Xu

On 22/6/2021 5:01 pm, Yang Weijiang wrote:
> 
> Hello, maintainers,
> 
> I took over the work from Like and will carry it forward. Here I'd like to
> get your valuable comments on this patch series before I post next version.
> 
> Thanks a lot!
> 
>> Hi geniuses,
>>
>> A new kernel cycle has begun, and this version looks promising.
>>
>> >From the end user's point of view, the usage of Arch LBR is the same as
>> the legacy LBR we have merged in the mainline, but it is much faster.
>>
>> The Architectural Last Branch Records (LBRs) is published
>> in the 319433-040 release of Intel Architecture Instruction
>> Set Extensions and Future Features Programming Reference[0].
>>
>> The main advantages for the Arch LBR users are [1]:
>> - Faster context switching due to XSAVES support and faster reset of
>>    LBR MSRs via the new DEPTH MSR
>> - Faster LBR read for a non-PEBS event due to XSAVES support, which
>>    lowers the overhead of the NMI handler.
>> - Linux kernel can support the LBR features without knowing the model
>>    number of the current CPU.
>>
>> Please check more details in each commit and feel free to comment.
>>
>> [0] https://software.intel.com/content/www/us/en/develop/download/
>> intel-architecture-instruction-set-extensions-and-future-features-programming-reference.html
>> [1] https://lore.kernel.org/lkml/1593780569-62993-1-git-send-email-kan.liang@linux.intel.com/
>>
>> ---
>> v13->v13 RESEND Changelog:
>> - Rebase to kvm/queue tree tag: kvm-5.13-2;
>> - Includes two XSS dependency patches from kvm/intel tree;
>>
>> v3->v4 Changelog:
>> - Add one more host patch to reuse ARCH_LBR_CTL_MASK;
>> - Add reserve_lbr_buffers() instead of using GFP_ATOMIC;
>> - Fia a bug in the arch_lbr_depth_is_valid();
>> - Add LBR_CTL_EN to unify DEBUGCTLMSR_LBR and ARCH_LBR_CTL_LBREN;
>> - Add vmx->host_lbrctlmsr to save/restore host values;
>> - Add KVM_SUPPORTED_XSS to refactoring supported_xss;
>> - Clear Arch_LBR ans its XSS bit if it's not supported;
>> - Add negative testing to the related kvm-unit-tests;
>> - Refine code and commit messages;
>>
>> Previous:
>> v4: https://lore.kernel.org/kvm/20210314155225.206661-1-like.xu@linux.intel.com/
>> v3: https://lore.kernel.org/kvm/20210303135756.1546253-1-like.xu@linux.intel.com/
>>
>> Like Xu (8):
>>    perf/x86/intel: Fix the comment about guest LBR support on KVM
>>    perf/x86/lbr: Simplify the exposure check for the LBR_INFO registers
>>    KVM: vmx/pmu: Add MSR_ARCH_LBR_DEPTH emulation for Arch LBR
>>    KVM: vmx/pmu: Add MSR_ARCH_LBR_CTL emulation for Arch LBR
>>    KVM: vmx/pmu: Add Arch LBR emulation and its VMCS field
>>    KVM: x86: Expose Architectural LBR CPUID leaf
>>    KVM: x86: Refine the matching and clearing logic for supported_xss
>>    KVM: x86: Add XSAVE Support for Architectural LBRs
>>
>> Sean Christopherson (1):
>>    KVM: x86: Report XSS as an MSR to be saved if there are supported
>>      features
>>
>> Yang Weijiang (1):
>>    KVM: x86: Refresh CPUID on writes to MSR_IA32_XSS
>>
>>   arch/x86/events/intel/core.c     |   3 +-
>>   arch/x86/events/intel/lbr.c      |   6 +-
>>   arch/x86/include/asm/kvm_host.h  |   1 +
>>   arch/x86/include/asm/msr-index.h |   1 +
>>   arch/x86/include/asm/vmx.h       |   4 ++
>>   arch/x86/kvm/cpuid.c             |  46 ++++++++++++--
>>   arch/x86/kvm/vmx/capabilities.h  |  25 +++++---
>>   arch/x86/kvm/vmx/pmu_intel.c     | 103 ++++++++++++++++++++++++++++---
>>   arch/x86/kvm/vmx/vmx.c           |  50 +++++++++++++--
>>   arch/x86/kvm/vmx/vmx.h           |   4 ++
>>   arch/x86/kvm/x86.c               |  19 +++++-
>>   11 files changed, 226 insertions(+), 36 deletions(-)
>>
>> -- 
>> 2.31.1
>