[RESEND,v3,01/11] KVM: x86/pmu: Update comments for AMD gp counters

Commit Message

Like Xu May 18, 2022, 1:25 p.m. UTC

From: Like Xu <[e-mail]>

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 <[e-mail]>
---
 arch/x86/kvm/pmu.c | 7 +++++--
 1 file changed, 5 insertions(+), 2 deletions(-)

Patch

diff --git a/arch/x86/kvm/pmu.c b/arch/x86/kvm/pmu.c
index b5d0c36b869b..3e200b9610f9 100644
--- a/arch/x86/kvm/pmu.c
+++ b/arch/x86/kvm/pmu.c
@@ -37,7 +37,9 @@  EXPORT_SYMBOL_GPL(kvm_pmu_cap);
  *   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
@@ -49,7 +51,8 @@  EXPORT_SYMBOL_GPL(kvm_pmu_cap);
  *        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;