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KVM: x86/pmu: Explicitly check for RDPMC of unsupported Intel PMC types

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Explicitly check for attempts to read unsupported PMC types instead of
letting the bounds check fail.  Functionally, letting the check fail is
ok, but it's unnecessarily subtle and does a poor job of documenting the
architectural behavior that KVM is emulating.

Reviewed-by: Dapeng Mi  <dapeng1.mi@linux.intel.com>
Tested-by: Dapeng Mi <dapeng1.mi@linux.intel.com>
Link: https://lore.kernel.org/r/20240109230250.424295-12-seanjc@google.com
Signed-off-by: Sean Christopherson <seanjc@google.com>
This commit is contained in:
Sean Christopherson
2024-01-09 15:02:31 -08:00
parent 7a0fc734c2
commit a634c76b2c
1 changed files with 15 additions and 6 deletions
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21
arch/x86/kvm/vmx/pmu_intel.c
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@@ -26,6 +26,7 @@
* further confuse things, non-architectural PMUs use bit 31 as a flag for
* "fast" reads, whereas the "type" is an explicit value.
*/
#define INTEL_RDPMC_GP 0
#define INTEL_RDPMC_FIXED INTEL_PMC_FIXED_RDPMC_BASE
#define INTEL_RDPMC_TYPE_MASK GENMASK(31, 16)
@@ -89,21 +90,29 @@ static struct kvm_pmc *intel_rdpmc_ecx_to_pmc(struct kvm_vcpu *vcpu,
return NULL;
/*
* Fixed PMCs are supported on all architectural PMUs. Note, KVM only
* emulates fixed PMCs for PMU v2+, but the flag itself is still valid,
* i.e. let RDPMC fail due to accessing a non-existent counter.
* General Purpose (GP) PMCs are supported on all PMUs, and fixed PMCs
* are supported on all architectural PMUs, i.e. on all virtual PMUs
* supported by KVM. Note, KVM only emulates fixed PMCs for PMU v2+,
* but the type itself is still valid, i.e. let RDPMC fail due to
* accessing a non-existent counter. Reject attempts to read all other
* types, which are unknown/unsupported.
*/
idx &= ~INTEL_RDPMC_FIXED;
if (type == INTEL_RDPMC_FIXED) {
switch (type) {
case INTEL_RDPMC_FIXED:
counters = pmu->fixed_counters;
num_counters = pmu->nr_arch_fixed_counters;
bitmask = pmu->counter_bitmask[KVM_PMC_FIXED];
} else {
break;
case INTEL_RDPMC_GP:
counters = pmu->gp_counters;
num_counters = pmu->nr_arch_gp_counters;
bitmask = pmu->counter_bitmask[KVM_PMC_GP];
break;
default:
return NULL;
}
idx &= INTEL_RDPMC_INDEX_MASK;
if (idx >= num_counters)
return NULL;