linux-kernel - Re: [PATCH 00/15] Introduce Architectural LBR for vPMU

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Message-ID: <c44cbee1-663e-4bc3-357d-d683c4721565@intel.com>
Date:   Fri, 21 Oct 2022 10:14:21 +0800
From:   "Yang, Weijiang" <weijiang.yang@...el.com>
To:     Sean Christopherson <seanjc@...gle.com>
CC:     "pbonzini@...hat.com" <pbonzini@...hat.com>,
        "kvm@...r.kernel.org" <kvm@...r.kernel.org>,
        "like.xu.linux@...il.com" <like.xu.linux@...il.com>,
        "kan.liang@...ux.intel.com" <kan.liang@...ux.intel.com>,
        "Wang, Wei W" <wei.w.wang@...el.com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 00/15] Introduce Architectural LBR for vPMU


On 9/2/2022 11:44 AM, Yang, Weijiang wrote:
>
> On 9/1/2022 10:23 PM, Sean Christopherson wrote:
>> On Wed, Aug 31, 2022, Yang Weijiang wrote:
>>> The old patch series was queued in KVM/queue for a while and finally
>>> moved to below branch after Paolo's refactor. This new patch set is
>>> built on top of Paolo's work + some fixes, it's tested on legacy 
>>> platform
>> Please elaborate on what was broken, i.e. why this was de-queued, as 
>> well as on
>> what was fixed an dhow.  That will help bring me up to speed and 
>> expedite review.
> Thanks Sean!
> The de-queued reason I read from community is, the PEBS and Arch-LBR 
> patches broke
> selftest/KUTs due to host-initiated 0 writes to PMU msrs. Paolo tried 
> to fix it but you
> didn't agree on the solution. Plus your comments below:
>
>
> On 6/1/2022 4:54 PM, Paolo Bonzini wrote:
> > On 5/31/22 20:37, Sean Christopherson wrote:
> >> Can we just punt this out of kvm/queue until its been properly 
> reviewed?
> > Yes, I agree.  I have started making some changes and pushed the
> > result to kvm/arch-lbr-for-weijiang.
>
> What are fixed in this series:
>
> 1.  An missing of -1: if ((entry->eax & 0xff) != (1 << (depth_bit - 1)))
>
> 2.  Removed exit bit check in  cpu_has_vmx_arch_lbr(void), moved it to 
> setup_vmcs_config().
>
> 3.  A redundant check kvm_cpu_cap_has(X86_FEATURE_ARCH_LBR) in 
> kvm_check_cpuid().
>
> 4.  KUT/selftest failures due to lack of MSR_ARCH_LBR_CTL and 
> MSR_ARCH_LBR_DEPTH in kvm_set_msr_common() before validate pmu msrs.
>
> 5.  Calltrace in L1 when L1 tried to vmcs_write64(GUEST_IA32_LBR_CTL, 
> 0) in vmx_vcpu_reset(), use cpu_has_vmx_arch_lbr() instead.
>
> 6.  Removed VM_ENTRY_LOAD_IA32_LBR_CTL and VM_EXIT_CLEAR_IA32_LBR_CTL 
> from exec_control in nested case.
>
Hi, Sean,

Could you kindly review this post and give some comments on the series 
so that I can prepare next version?

Thanks!