Re: [PATCH 00/10] KVM: x86/pmu: Optimize triggering of emulated events

Sean Christopherson
2024-02-03T00:13:25Z

On Thu, 09 Nov 2023 18:28:47 -0800, Sean Christopherson wrote:
> Optimize code used by, or which impacts, kvm_pmu_trigger_event() to try
> and make a dent in the overhead of emulating PMU events in software, which
> is quite noticeable due to it kicking in anytime the guest has a vPMU and
> KVM is skipping an instruction.
>
> Note, Jim has a proposal/idea[*] (that I supported) to make
> kvm_pmu_trigger_event() even more performant. I opted not to do that as
> it's a bit more invasive, and I started chewing on this not so much because
> I care _that_ much about performance, but because it irritates me that the
> PMU code makes things way harder than they need to be.
>
> [...]

Applied to kvm-x86 pmu, thanks!

[01/10] KVM: x86/pmu: Zero out PMU metadata on AMD if PMU is disabled
https://github.com/kvm-x86/linux/commit/f933b88e2015
[02/10] KVM: x86/pmu: Add common define to capture fixed counters offset
https://github.com/kvm-x86/linux/commit/be6b067dae15
[03/10] KVM: x86/pmu: Move pmc_idx => pmc translation helper to common code
https://github.com/kvm-x86/linux/commit/b31880ca2f41
[04/10] KVM: x86/pmu: Snapshot and clear reprogramming bitmap before reprogramming
https://github.com/kvm-x86/linux/commit/004a0aa56ede
[05/10] KVM: x86/pmu: Add macros to iterate over all PMCs given a bitmap
https://github.com/kvm-x86/linux/commit/e5a65d4f723a
[06/10] KVM: x86/pmu: Process only enabled PMCs when emulating events in software
https://github.com/kvm-x86/linux/commit/d2b321ea9380
[07/10] KVM: x86/pmu: Snapshot event selectors that KVM emulates in software
https://github.com/kvm-x86/linux/commit/f19063b1ca05
[08/10] KVM: x86/pmu: Expand the comment about what bits are check emulating events
https://github.com/kvm-x86/linux/commit/afda2d7666f8
[09/10] KVM: x86/pmu: Check eventsel first when emulating (branch) insns retired
https://github.com/kvm-x86/linux/commit/e35529fb4ac9
[10/10] KVM: x86/pmu: Avoid CPL lookup if PMC enabline for USER and KERNEL is the same
https://github.com/kvm-x86/linux/commit/83bdfe04c968

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