On 12/6/21 20:57, Jim Mattson wrote:
+
+ for (i = 0; i < pmu->nr_arch_fixed_counters; i++) {
+ pmc = &pmu->fixed_counters[i];
+ event = fixed_pmc_events[array_index_nospec(i, size)];
How do we know that i < size? For example, Ice Lake supports 4 fixed
counters, but fixed_pmc_events only has three entries.
We don't, and it's a preexisting bug in intel_pmu_refresh. Either we hack around it like
diff --git a/arch/x86/kvm/vmx/pmu_intel.c b/arch/x86/kvm/vmx/pmu_intel.c
index 1b7456b2177b..6f03c8bf1bc2 100644
--- a/arch/x86/kvm/vmx/pmu_intel.c
+++ b/arch/x86/kvm/vmx/pmu_intel.c
@@ -500,8 +500,9 @@ static void intel_pmu_refresh(struct kvm_vcpu *vcpu)
pmu->nr_arch_fixed_counters = 0;
} else {
pmu->nr_arch_fixed_counters =
- min_t(int, edx.split.num_counters_fixed,
- x86_pmu.num_counters_fixed);
+ min3(ARRAY_SIZE(fixed_pmc_events),
+ (size_t) edx.split.num_counters_fixed,
+ (size_t) x86_pmu.num_counters_fixed);
edx.split.bit_width_fixed = min_t(int,
edx.split.bit_width_fixed, x86_pmu.bit_width_fixed);
pmu->counter_bitmask[KVM_PMC_FIXED] =
or we modify find_fixed_event and its caller to support PERF_TYPE_RAW
counters, and then add support for the IceLake TOPDOWN.SLOTS fixed
counter.
What's your preference?
Paolo
