linux-kernel - Re: [RFC PATCH 00/41] KVM: x86/pmu: Introduce passthrough vPM

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Message-ID: <CAL715WLYN+S2Nk4OrqEuCMmyQypZt6r+WOyv1YYXfi+Moo--Mw@mail.gmail.com>
Date: Thu, 11 Apr 2024 16:56:41 -0700
From: Mingwei Zhang <mizhang@...gle.com>
To: Sean Christopherson <seanjc@...gle.com>
Cc: Xiong Zhang <xiong.y.zhang@...ux.intel.com>, pbonzini@...hat.com, 
	peterz@...radead.org, kan.liang@...el.com, zhenyuw@...ux.intel.com, 
	dapeng1.mi@...ux.intel.com, jmattson@...gle.com, kvm@...r.kernel.org, 
	linux-perf-users@...r.kernel.org, linux-kernel@...r.kernel.org, 
	zhiyuan.lv@...el.com, eranian@...gle.com, irogers@...gle.com, 
	samantha.alt@...el.com, like.xu.linux@...il.com, chao.gao@...el.com
Subject: Re: [RFC PATCH 00/41] KVM: x86/pmu: Introduce passthrough vPM

Hi Sean,

On Thu, Apr 11, 2024 at 4:26 PM Sean Christopherson <seanjc@...gle.com> wrote:
>
> On Fri, Jan 26, 2024, Xiong Zhang wrote:
> > Dapeng Mi (4):
> >   x86: Introduce MSR_CORE_PERF_GLOBAL_STATUS_SET for passthrough PMU
> >   KVM: x86/pmu: Implement the save/restore of PMU state for Intel CPU
> >   KVM: x86/pmu: Introduce macro PMU_CAP_PERF_METRICS
> >   KVM: x86/pmu: Clear PERF_METRICS MSR for guest
> >
> > Kan Liang (2):
> >   perf: x86/intel: Support PERF_PMU_CAP_VPMU_PASSTHROUGH
> >   perf: Support guest enter/exit interfaces
> >
> > Mingwei Zhang (22):
> >   perf: core/x86: Forbid PMI handler when guest own PMU
> >   perf: core/x86: Plumb passthrough PMU capability from x86_pmu to
> >     x86_pmu_cap
> >   KVM: x86/pmu: Introduce enable_passthrough_pmu module parameter and
> >     propage to KVM instance
> >   KVM: x86/pmu: Plumb through passthrough PMU to vcpu for Intel CPUs
> >   KVM: x86/pmu: Add a helper to check if passthrough PMU is enabled
> >   KVM: x86/pmu: Allow RDPMC pass through
> >   KVM: x86/pmu: Create a function prototype to disable MSR interception
> >   KVM: x86/pmu: Implement pmu function for Intel CPU to disable MSR
> >     interception
> >   KVM: x86/pmu: Intercept full-width GP counter MSRs by checking with
> >     perf capabilities
> >   KVM: x86/pmu: Whitelist PMU MSRs for passthrough PMU
> >   KVM: x86/pmu: Introduce PMU operation prototypes for save/restore PMU
> >     context
> >   KVM: x86/pmu: Introduce function prototype for Intel CPU to
> >     save/restore PMU context
> >   KVM: x86/pmu: Zero out unexposed Counters/Selectors to avoid
> >     information leakage
> >   KVM: x86/pmu: Add host_perf_cap field in kvm_caps to record host PMU
> >     capability
> >   KVM: x86/pmu: Exclude existing vLBR logic from the passthrough PMU
> >   KVM: x86/pmu: Make check_pmu_event_filter() an exported function
> >   KVM: x86/pmu: Allow writing to event selector for GP counters if event
> >     is allowed
> >   KVM: x86/pmu: Allow writing to fixed counter selector if counter is
> >     exposed
> >   KVM: x86/pmu: Introduce PMU helper to increment counter
> >   KVM: x86/pmu: Implement emulated counter increment for passthrough PMU
> >   KVM: x86/pmu: Separate passthrough PMU logic in set/get_msr() from
> >     non-passthrough vPMU
> >   KVM: nVMX: Add nested virtualization support for passthrough PMU
> >
> > Xiong Zhang (13):
> >   perf: Set exclude_guest onto nmi_watchdog
> >   perf: core/x86: Add support to register a new vector for PMI handling
> >   KVM: x86/pmu: Register PMI handler for passthrough PMU
> >   perf: x86: Add function to switch PMI handler
> >   perf/x86: Add interface to reflect virtual LVTPC_MASK bit onto HW
> >   KVM: x86/pmu: Add get virtual LVTPC_MASK bit function
> >   KVM: x86/pmu: Manage MSR interception for IA32_PERF_GLOBAL_CTRL
> >   KVM: x86/pmu: Switch IA32_PERF_GLOBAL_CTRL at VM boundary
> >   KVM: x86/pmu: Switch PMI handler at KVM context switch boundary
> >   KVM: x86/pmu: Call perf_guest_enter() at PMU context switch
> >   KVM: x86/pmu: Add support for PMU context switch at VM-exit/enter
> >   KVM: x86/pmu: Intercept EVENT_SELECT MSR
> >   KVM: x86/pmu: Intercept FIXED_CTR_CTRL MSR
>
> All done with this pass.  Looks quite good, nothing on the KVM side scares me.  Nice!

yay! Thank you Sean for the review!

>
> I haven't spent much time thinking about whether or not the overall implementation
> correct/optimal, i.e. I mostly just reviewed the mechanics.  I'll make sure to
> spend a bit more time on that for the next RFC.

Yes, I am expecting the debate/discussion in PUCK after v2 is sent
out. There should be room for optimization as well.

>
> Please be sure to rebase to kvm-x86/next for the next RFC, there are a few patches
> that will change quite a bit.

Will do the rebase and all of the feedback will be taken and into
updates in v2. In v2, we will incorporate passthrough vPMU with AMD
support. Will do our best to get it in high quality.

Thanks.
-Mingwei