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KVM: x86/pmu: Update comments for AMD gp counters

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The obsolete comment could more accurately state that AMD platforms
have two base MSR addresses and two different maximum numbers
for gp counters, depending on the X86_FEATURE_PERFCTR_CORE feature.

Signed-off-by: Like Xu <likexu@tencent.com>
Message-Id: <20220518132512.37864-2-likexu@tencent.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
This commit is contained in:
Like Xu 2022-05-18 21:25:02 +08:00 committed by Paolo Bonzini
parent d1c88a4020
commit a33095f493
1 changed files with 5 additions and 2 deletions
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7
arch/x86/kvm/pmu.c
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@ -44,7 +44,9 @@ static const struct x86_cpu_id vmx_icl_pebs_cpu[] = {
* However AMD doesn't support fixed-counters;
* - There are three types of index to access perf counters (PMC):
* 1. MSR (named msr): For example Intel has MSR_IA32_PERFCTRn and AMD
* has MSR_K7_PERFCTRn.
* has MSR_K7_PERFCTRn and, for families 15H and later,
* MSR_F15H_PERF_CTRn, where MSR_F15H_PERF_CTR[0-3] are
* aliased to MSR_K7_PERFCTRn.
* 2. MSR Index (named idx): This normally is used by RDPMC instruction.
* For instance AMD RDPMC instruction uses 0000_0003h in ECX to access
* C001_0007h (MSR_K7_PERCTR3). Intel has a similar mechanism, except
@ -56,7 +58,8 @@ static const struct x86_cpu_id vmx_icl_pebs_cpu[] = {
* between pmc and perf counters is as the following:
* * Intel: [0 .. INTEL_PMC_MAX_GENERIC-1] <=> gp counters
* [INTEL_PMC_IDX_FIXED .. INTEL_PMC_IDX_FIXED + 2] <=> fixed
* * AMD: [0 .. AMD64_NUM_COUNTERS-1] <=> gp counters
* * AMD: [0 .. AMD64_NUM_COUNTERS-1] and, for families 15H
* and later, [0 .. AMD64_NUM_COUNTERS_CORE-1] <=> gp counters
*/
static struct kvm_pmu_ops kvm_pmu_ops __read_mostly;