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KVM: x86/pmu: Apply "fast" RDPMC only to Intel PMUs

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Move the handling of "fast" RDPMC instructions, which drop bits 63:32 of
the count, to Intel.  The "fast" flag, and all modifiers for that matter,
are Intel-only and aren't supported by AMD.

Opportunistically replace open coded bit crud with proper #defines, and
add comments to try and disentangle the flags vs. values mess for
non-architectural vs. architectural PMUs.

Fixes: ca724305a2 ("KVM: x86/vPMU: Implement AMD vPMU code for KVM")
Reviewed-by: Dapeng Mi <dapeng1.mi@linux.intel.com>
Tested-by: Dapeng Mi <dapeng1.mi@linux.intel.com>
Link: https://lore.kernel.org/r/20240109230250.424295-9-seanjc@google.com
Signed-off-by: Sean Christopherson <seanjc@google.com>
This commit is contained in:
Sean Christopherson 2024-01-09 15:02:28 -08:00
parent 7bb7fce136
commit d652981db0
2 changed files with 15 additions and 4 deletions
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3
arch/x86/kvm/pmu.c
View File

@ -576,10 +576,9 @@ static int kvm_pmu_rdpmc_vmware(struct kvm_vcpu *vcpu, unsigned idx, u64 *data)
int kvm_pmu_rdpmc(struct kvm_vcpu *vcpu, unsigned idx, u64 *data)
{
bool fast_mode = idx & (1u << 31);
struct kvm_pmu *pmu = vcpu_to_pmu(vcpu);
struct kvm_pmc *pmc;
u64 mask = fast_mode ? ~0u : ~0ull;
u64 mask = ~0ull;
if (!pmu->version)
return 1;

16
arch/x86/kvm/vmx/pmu_intel.c
View File

@ -20,6 +20,15 @@
#include "nested.h"
#include "pmu.h"
/*
* Perf's "BASE" is wildly misleading, architectural PMUs use bits 31:16 of ECX
* to encode the "type" of counter to read, i.e. this is not a "base". And to
* 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_FIXED INTEL_PMC_FIXED_RDPMC_BASE
#define INTEL_RDPMC_FAST BIT(31)
#define MSR_PMC_FULL_WIDTH_BIT (MSR_IA32_PMC0 - MSR_IA32_PERFCTR0)
static void reprogram_fixed_counters(struct kvm_pmu *pmu, u64 data)
@ -59,11 +68,14 @@ static struct kvm_pmc *intel_rdpmc_ecx_to_pmc(struct kvm_vcpu *vcpu,
unsigned int idx, u64 *mask)
{
struct kvm_pmu *pmu = vcpu_to_pmu(vcpu);
bool fixed = idx & (1u << 30);
bool fixed = idx & INTEL_RDPMC_FIXED;
struct kvm_pmc *counters;
unsigned int num_counters;
idx &= ~(3u << 30);
if (idx & INTEL_RDPMC_FAST)
*mask &= GENMASK_ULL(31, 0);
idx &= ~(INTEL_RDPMC_FIXED | INTEL_RDPMC_FAST);
if (fixed) {
counters = pmu->fixed_counters;
num_counters = pmu->nr_arch_fixed_counters;