linux-kernel - [Patch 1/2] KVM: x86/pmu: Add Intel CPUID-hinted TopDown slots event

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Message-Id: <20231031090613.2872700-2-dapeng1.mi@linux.intel.com>
Date:   Tue, 31 Oct 2023 17:06:12 +0800
From:   Dapeng Mi <dapeng1.mi@...ux.intel.com>
To:     Sean Christopherson <seanjc@...gle.com>,
        Paolo Bonzini <pbonzini@...hat.com>
Cc:     kvm@...r.kernel.org, linux-kernel@...r.kernel.org,
        Zhenyu Wang <zhenyuw@...ux.intel.com>,
        Zhang Xiong <xiong.y.zhang@...el.com>,
        Jim Mattson <jmattson@...gle.com>,
        Mingwei Zhang <mizhang@...gle.com>,
        Like Xu <like.xu.linux@...il.com>,
        Dapeng Mi <dapeng1.mi@...el.com>,
        Dapeng Mi <dapeng1.mi@...ux.intel.com>,
        Like Xu <likexu@...cent.com>
Subject: [Patch 1/2] KVM: x86/pmu: Add Intel CPUID-hinted TopDown slots event

This patch adds support for the architectural topdown slots event which
is hinted by CPUID.0AH.EBX.

The topdown slots event counts the total number of available slots for
an unhalted logical processor. Software can use this event as the
denominator for the top-level metrics of the topDown Microarchitecture
Analysis method.

Although the MSR_PERF_METRICS MSR required for topdown events is not
currently available in the guest, relying only on the data provided by
the slots event is sufficient for pmu users to perceive differences in
cpu pipeline machine-width across micro-architectures.

The standalone slots event, like the instruction event, can be counted
with gp counter or fixed counter 3 (if any). Its availability is also
controlled by CPUID.AH.EBX. On Linux, perf user may encode
"-e cpu/event=0xa4,umask=0x01/" or "-e cpu/slots/" to count slots events.

This patch only enables slots event on GP counters. The enabling on fixed
counter 3 will be supported in subsequent patches.

Co-developed-by: Like Xu <likexu@...cent.com>
Signed-off-by: Like Xu <likexu@...cent.com>
Signed-off-by: Dapeng Mi <dapeng1.mi@...ux.intel.com>
---
 arch/x86/kvm/vmx/pmu_intel.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/arch/x86/kvm/vmx/pmu_intel.c b/arch/x86/kvm/vmx/pmu_intel.c
index 820d3e1f6b4f..e32353f1143f 100644
--- a/arch/x86/kvm/vmx/pmu_intel.c
+++ b/arch/x86/kvm/vmx/pmu_intel.c
@@ -34,6 +34,7 @@ enum intel_pmu_architectural_events {
 	INTEL_ARCH_LLC_MISSES,
 	INTEL_ARCH_BRANCHES_RETIRED,
 	INTEL_ARCH_BRANCHES_MISPREDICTED,
+	INTEL_ARCH_TOPDOWN_SLOTS,

 	NR_REAL_INTEL_ARCH_EVENTS,

@@ -58,6 +59,7 @@ static struct {
 	[INTEL_ARCH_LLC_MISSES]			= { 0x2e, 0x41 },
 	[INTEL_ARCH_BRANCHES_RETIRED]		= { 0xc4, 0x00 },
 	[INTEL_ARCH_BRANCHES_MISPREDICTED]	= { 0xc5, 0x00 },
+	[INTEL_ARCH_TOPDOWN_SLOTS]		= { 0xa4, 0x01 },
 	[PSEUDO_ARCH_REFERENCE_CYCLES]		= { 0x00, 0x03 },
 };

-- 
2.34.1