linux-kernel - [PATCH] KVM: x86/pmu: Fix emulation on counters' bit width

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Date:   Thu, 16 Mar 2023 19:33:12 +0800
From:   Like Xu <like.xu.linux@...il.com>
To:     Sean Christopherson <seanjc@...gle.com>
Cc:     Paolo Bonzini <pbonzini@...hat.com>, kvm@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: [PATCH] KVM: x86/pmu: Fix emulation on counters' bit width

From: Like Xu <likexu@...cent.com>

According to the latest Intel SDM, the bit width of a PMU counter
is specified via CPUID only if the vCPU has FW_WRITE[bit 13] on
IA32_PERF_CAPABILITIES. Moreover, if this bit is deliberately removed
from KVM's user space, the only valid value written to is EAX[31:0].

Opportunistically BIT_ULL() is applied.

Signed-off-by: Like Xu <likexu@...cent.com>
---
 arch/x86/kvm/svm/pmu.c       | 2 +-
 arch/x86/kvm/vmx/pmu_intel.c | 6 ++++--
 2 files changed, 5 insertions(+), 3 deletions(-)

diff --git a/arch/x86/kvm/svm/pmu.c b/arch/x86/kvm/svm/pmu.c
index cc77a0681800..0d45dc55326b 100644
--- a/arch/x86/kvm/svm/pmu.c
+++ b/arch/x86/kvm/svm/pmu.c
@@ -178,7 +178,7 @@ static void amd_pmu_refresh(struct kvm_vcpu *vcpu)
 	else
 		pmu->nr_arch_gp_counters = AMD64_NUM_COUNTERS;
 
-	pmu->counter_bitmask[KVM_PMC_GP] = ((u64)1 << 48) - 1;
+	pmu->counter_bitmask[KVM_PMC_GP] = BIT_ULL(48) - 1;
 	pmu->reserved_bits = 0xfffffff000280000ull;
 	pmu->raw_event_mask = AMD64_RAW_EVENT_MASK;
 	pmu->version = 1;
diff --git a/arch/x86/kvm/vmx/pmu_intel.c b/arch/x86/kvm/vmx/pmu_intel.c
index e8a3be0b9df9..1c9d87856c37 100644
--- a/arch/x86/kvm/vmx/pmu_intel.c
+++ b/arch/x86/kvm/vmx/pmu_intel.c
@@ -516,6 +516,7 @@ static void intel_pmu_refresh(struct kvm_vcpu *vcpu)
 	union cpuid10_edx edx;
 	u64 perf_capabilities;
 	u64 counter_mask;
+	bool fw_wr = fw_writes_is_enabled(vcpu);
 	int i;
 
 	pmu->nr_arch_gp_counters = 0;
@@ -545,7 +546,8 @@ static void intel_pmu_refresh(struct kvm_vcpu *vcpu)
 					 kvm_pmu_cap.num_counters_gp);
 	eax.split.bit_width = min_t(int, eax.split.bit_width,
 				    kvm_pmu_cap.bit_width_gp);
-	pmu->counter_bitmask[KVM_PMC_GP] = ((u64)1 << eax.split.bit_width) - 1;
+	pmu->counter_bitmask[KVM_PMC_GP] =
+		BIT_ULL(fw_wr ? eax.split.bit_width : 32) - 1;
 	eax.split.mask_length = min_t(int, eax.split.mask_length,
 				      kvm_pmu_cap.events_mask_len);
 	pmu->available_event_types = ~entry->ebx &
@@ -561,7 +563,7 @@ static void intel_pmu_refresh(struct kvm_vcpu *vcpu)
 		edx.split.bit_width_fixed = min_t(int, edx.split.bit_width_fixed,
 						  kvm_pmu_cap.bit_width_fixed);
 		pmu->counter_bitmask[KVM_PMC_FIXED] =
-			((u64)1 << edx.split.bit_width_fixed) - 1;
+			BIT_ULL(fw_wr ? edx.split.bit_width_fixed : 32) - 1;
 		setup_fixed_pmc_eventsel(pmu);
 	}
 

base-commit: eeac8ede17557680855031c6f305ece2378af326
-- 
2.39.2