linux-kernel - [PATCH v8 07/26] KVM: x86/pmu: Apply "fast" RDPMC only to Intel PMUs

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Message-ID: <20231110021306.1269082-8-seanjc@google.com>
Date:   Thu,  9 Nov 2023 18:12:47 -0800
From:   Sean Christopherson <seanjc@...gle.com>
To:     Sean Christopherson <seanjc@...gle.com>,
        Paolo Bonzini <pbonzini@...hat.com>
Cc:     kvm@...r.kernel.org, linux-kernel@...r.kernel.org,
        Kan Liang <kan.liang@...ux.intel.com>,
        Dapeng Mi <dapeng1.mi@...ux.intel.com>,
        Jim Mattson <jmattson@...gle.com>,
        Jinrong Liang <cloudliang@...cent.com>,
        Aaron Lewis <aaronlewis@...gle.com>,
        Like Xu <likexu@...cent.com>
Subject: [PATCH v8 07/26] KVM: x86/pmu: Apply "fast" RDPMC only to Intel PMUs

Move the handling of "fast" RDPMC instructions, which drop bits 63:31 of
the count, to Intel.  The "fast" flag, and all flags for that matter, are
Intel-only and aren't supported by AMD.

Opportunistically replace open coded bit crud with proper #defines.

Fixes: ca724305a2b0 ("KVM: x86/vPMU: Implement AMD vPMU code for KVM")
Signed-off-by: Sean Christopherson <seanjc@...gle.com>
---
 arch/x86/kvm/pmu.c           |  3 +--
 arch/x86/kvm/vmx/pmu_intel.c | 20 ++++++++++++++++----
 2 files changed, 17 insertions(+), 6 deletions(-)

diff --git a/arch/x86/kvm/pmu.c b/arch/x86/kvm/pmu.c
index 99ed72966528..e3ba5e12c2e7 100644
--- a/arch/x86/kvm/pmu.c
+++ b/arch/x86/kvm/pmu.c
@@ -499,10 +499,9 @@ static int kvm_pmu_rdpmc_vmware(struct kvm_vcpu *vcpu, unsigned idx, u64 *data)
 
 int kvm_pmu_rdpmc(struct kvm_vcpu *vcpu, unsigned idx, u64 *data)
 {
-	bool fast_mode = idx & (1u << 31);
 	struct kvm_pmu *pmu = vcpu_to_pmu(vcpu);
 	struct kvm_pmc *pmc;
-	u64 mask = fast_mode ? ~0u : ~0ull;
+	u64 mask = ~0ull;
 
 	if (!pmu->version)
 		return 1;
diff --git a/arch/x86/kvm/vmx/pmu_intel.c b/arch/x86/kvm/vmx/pmu_intel.c
index 3bac3b32b485..c6ea128ea7c8 100644
--- a/arch/x86/kvm/vmx/pmu_intel.c
+++ b/arch/x86/kvm/vmx/pmu_intel.c
@@ -20,6 +20,10 @@
 #include "nested.h"
 #include "pmu.h"
 
+/* Perf's "BASE" is wildly misleading, this is a single-bit flag, not a base. */
+#define INTEL_RDPMC_FIXED	INTEL_PMC_FIXED_RDPMC_BASE
+#define INTEL_RDPMC_FAST	BIT(31)
+
 #define MSR_PMC_FULL_WIDTH_BIT      (MSR_IA32_PMC0 - MSR_IA32_PERFCTR0)
 
 static void reprogram_fixed_counters(struct kvm_pmu *pmu, u64 data)
@@ -55,12 +59,17 @@ static struct kvm_pmc *intel_pmc_idx_to_pmc(struct kvm_pmu *pmu, int pmc_idx)
 	}
 }
 
+static u32 intel_rdpmc_get_masked_idx(struct kvm_pmu *pmu, u32 idx)
+{
+	return idx & ~(INTEL_RDPMC_FIXED | INTEL_RDPMC_FAST);
+}
+
 static bool intel_is_valid_rdpmc_ecx(struct kvm_vcpu *vcpu, unsigned int idx)
 {
 	struct kvm_pmu *pmu = vcpu_to_pmu(vcpu);
-	bool fixed = idx & (1u << 30);
+	bool fixed = idx & INTEL_RDPMC_FIXED;
 
-	idx &= ~(3u << 30);
+	idx = intel_rdpmc_get_masked_idx(pmu, idx);
 
 	return fixed ? idx < pmu->nr_arch_fixed_counters
 		     : idx < pmu->nr_arch_gp_counters;
@@ -70,11 +79,14 @@ static struct kvm_pmc *intel_rdpmc_ecx_to_pmc(struct kvm_vcpu *vcpu,
 					    unsigned int idx, u64 *mask)
 {
 	struct kvm_pmu *pmu = vcpu_to_pmu(vcpu);
-	bool fixed = idx & (1u << 30);
+	bool fixed = idx & INTEL_RDPMC_FIXED;
 	struct kvm_pmc *counters;
 	unsigned int num_counters;
 
-	idx &= ~(3u << 30);
+	if (idx & INTEL_RDPMC_FAST)
+		*mask &= GENMASK_ULL(31, 0);
+
+	idx = intel_rdpmc_get_masked_idx(pmu, idx);
 	if (fixed) {
 		counters = pmu->fixed_counters;
 		num_counters = pmu->nr_arch_fixed_counters;
-- 
2.42.0.869.gea05f2083d-goog