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).

Link: https://lore.kernel.org/r/20230607010206.1425277-4-seanjc@google.com
Signed-off-by: Sean Christopherson <seanjc@google.com>

diff --git a/arch/x86/kvm/vmx/pmu_intel.c b/arch/x86/kvm/vmx/pmu_intel.c
index db23697..f2efa0b 100644 (file)
--- a/arch/x86/kvm/vmx/pmu_intel.c
+++ b/arch/x86/kvm/vmx/pmu_intel.c
@@ -468,16 +468,17 @@ 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;
        }
 }
 
@@ -538,10 +539,8 @@ 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] =