linux-kernel - [PATCH 3/4] KVM: x86/pmu: Require nr fixed_pmc

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Message-ID: <20230607010206.1425277-4-seanjc@google.com>
Date:   Tue,  6 Jun 2023 18:02:05 -0700
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,
        Aaron Lewis <aaronlewis@...gle.com>,
        Like Xu <like.xu.linux@...il.com>
Subject: [PATCH 3/4] KVM: x86/pmu: Require nr fixed_pmc_events to match nr max
 fixed counters

Assert that the number of known fixed_pmc_events matches the max number of
fixed counters supported by KVM, and clean up related code.

Opportunistically extend setup_fixed_pmc_eventsel()'s use of
array_index_nospec() to cover fixed_counters, as nr_arch_fixed_counters is
set based on userspace input (but capped using KVM-controlled values).

Signed-off-by: Sean Christopherson <seanjc@...gle.com>
---
 arch/x86/kvm/vmx/pmu_intel.c | 19 +++++++++----------
 1 file changed, 9 insertions(+), 10 deletions(-)

diff --git a/arch/x86/kvm/vmx/pmu_intel.c b/arch/x86/kvm/vmx/pmu_intel.c
index f281e634af3c..c0b0a721b97f 100644
--- a/arch/x86/kvm/vmx/pmu_intel.c
+++ b/arch/x86/kvm/vmx/pmu_intel.c
@@ -527,16 +527,17 @@ static int intel_pmu_set_msr(struct kvm_vcpu *vcpu, struct msr_data *msr_info)
 
 static void setup_fixed_pmc_eventsel(struct kvm_pmu *pmu)
 {
-	size_t size = ARRAY_SIZE(fixed_pmc_events);
-	struct kvm_pmc *pmc;
-	u32 event;
 	int i;
 
+	BUILD_BUG_ON(ARRAY_SIZE(fixed_pmc_events) != KVM_PMC_MAX_FIXED);
+
 	for (i = 0; i < pmu->nr_arch_fixed_counters; i++) {
-		pmc = &pmu->fixed_counters[i];
-		event = fixed_pmc_events[array_index_nospec(i, size)];
+		int index = array_index_nospec(i, KVM_PMC_MAX_FIXED);
+		struct kvm_pmc *pmc = &pmu->fixed_counters[index];
+		u32 event = fixed_pmc_events[index];
+
 		pmc->eventsel = (intel_arch_events[event].unit_mask << 8) |
-			intel_arch_events[event].eventsel;
+				 intel_arch_events[event].eventsel;
 	}
 }
 
@@ -597,10 +598,8 @@ static void intel_pmu_refresh(struct kvm_vcpu *vcpu)
 	if (pmu->version == 1) {
 		pmu->nr_arch_fixed_counters = 0;
 	} else {
-		pmu->nr_arch_fixed_counters =
-			min3(ARRAY_SIZE(fixed_pmc_events),
-			     (size_t) edx.split.num_counters_fixed,
-			     (size_t)kvm_pmu_cap.num_counters_fixed);
+		pmu->nr_arch_fixed_counters = min_t(int, edx.split.num_counters_fixed,
+						    kvm_pmu_cap.num_counters_fixed);
 		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] =
-- 
2.41.0.162.gfafddb0af9-goog