linux-kernel - Re: [PATCH v2 0/6] KVM: x86/pmu: Count two basic events for emulated instructions

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Date:   Thu, 9 Dec 2021 20:30:34 +0100
From:   Paolo Bonzini <pbonzini@...hat.com>
To:     Like Xu <like.xu.linux@...il.com>
Cc:     Sean Christopherson <seanjc@...gle.com>,
        Vitaly Kuznetsov <vkuznets@...hat.com>,
        Wanpeng Li <wanpengli@...cent.com>,
        Jim Mattson <jmattson@...gle.com>,
        Joerg Roedel <joro@...tes.org>, kvm@...r.kernel.org,
        linux-kernel@...r.kernel.org, Like Xu <likexu@...cent.com>
Subject: Re: [PATCH v2 0/6] KVM: x86/pmu: Count two basic events for emulated
 instructions

On 11/30/21 08:42, Like Xu wrote:
> Hi,
> 
> [ Jim is on holiday, so I'm here to continue this work. ]
> 
> Some cloud customers need accurate virtualization of two
> basic PMU events on x86 hardware: "instructions retired" and
> "branch instructions retired". The existing PMU virtualization code
> fails to account for instructions (e.g, CPUID) that are emulated by KVM.
> 
> Accurately virtualizing all PMU events for all microarchitectures is a
> herculean task, let's just stick to the two events covered by this set.
> 
> Eric Hankland wrote this code originally, but his plate is full, so Jim
> and I volunteered to shepherd the changes through upstream acceptance.
> 
> Thanks,
> 
> v1 -> v2 Changelog:
> - Include the patch set [1] and drop the intel_find_fixed_event(); [Paolo]
>    (we will fix the misleading Intel CPUID events in another patch set)
> - Drop checks for pmc->perf_event or event state or event type;
> - Increase a counter once its umask bits and the first 8 select bits are matched;
> - Rewrite kvm_pmu_incr_counter() with a less invasive approach to the host perf;
> - Rename kvm_pmu_record_event to kvm_pmu_trigger_event;
> - Add counter enable check for kvm_pmu_trigger_event();
> - Add vcpu CPL check for kvm_pmu_trigger_event(); [Jim]
> 
> Previous:
> https://lore.kernel.org/kvm/20211112235235.1125060-2-jmattson@google.com/
> 
> [1] https://lore.kernel.org/kvm/20211119064856.77948-1-likexu@tencent.com/
> 
> Jim Mattson (1):
>    KVM: x86: Update vPMCs when retiring branch instructions
> 
> Like Xu (5):
>    KVM: x86/pmu: Setup pmc->eventsel for fixed PMCs
>    KVM: x86/pmu: Refactoring find_arch_event() to pmc_perf_hw_id()
>    KVM: x86/pmu: Reuse pmc_perf_hw_id() and drop find_fixed_event()
>    KVM: x86/pmu: Add pmc->intr to refactor kvm_perf_overflow{_intr}()
>    KVM: x86: Update vPMCs when retiring instructions
> 
>   arch/x86/include/asm/kvm_host.h |   1 +
>   arch/x86/kvm/emulate.c          |  55 ++++++++------
>   arch/x86/kvm/kvm_emulate.h      |   1 +
>   arch/x86/kvm/pmu.c              | 128 ++++++++++++++++++++++----------
>   arch/x86/kvm/pmu.h              |   5 +-
>   arch/x86/kvm/svm/pmu.c          |  19 ++---
>   arch/x86/kvm/vmx/nested.c       |   7 +-
>   arch/x86/kvm/vmx/pmu_intel.c    |  44 ++++++-----
>   arch/x86/kvm/x86.c              |   5 ++
>   9 files changed, 167 insertions(+), 98 deletions(-)
> 

Queued patches 1-4, thanks.

Paolo