On Tue, Sep 6, 2022 at 8:59 PM Like Xu <like.xu.linux@xxxxxxxxx> wrote: > > On 7/9/2022 4:08 am, Jim Mattson wrote: > > On Tue, Sep 6, 2022 at 5:53 AM Like Xu <like.xu.linux@xxxxxxxxx> wrote: > >> > >> On 6/9/2022 1:36 am, Jim Mattson wrote: > >>> On Mon, Sep 5, 2022 at 5:45 AM Like Xu <like.xu.linux@xxxxxxxxx> wrote: > >>>> > >>>> From: Sandipan Das <sandipan.das@xxxxxxx> > >>>> > >>>> CPUID leaf 0x80000022 i.e. ExtPerfMonAndDbg advertises some > >>>> new performance monitoring features for AMD processors. > >>>> > >>>> Bit 0 of EAX indicates support for Performance Monitoring > >>>> Version 2 (PerfMonV2) features. If found to be set during > >>>> PMU initialization, the EBX bits of the same CPUID function > >>>> can be used to determine the number of available PMCs for > >>>> different PMU types. > >>>> > >>>> Expose the relevant bits via KVM_GET_SUPPORTED_CPUID so > >>>> that guests can make use of the PerfMonV2 features. > >>>> > >>>> Co-developed-by: Like Xu <likexu@xxxxxxxxxxx> > >>>> Signed-off-by: Like Xu <likexu@xxxxxxxxxxx> > >>>> Signed-off-by: Sandipan Das <sandipan.das@xxxxxxx> > >>>> --- > >>>> arch/x86/include/asm/perf_event.h | 8 ++++++++ > >>>> arch/x86/kvm/cpuid.c | 21 ++++++++++++++++++++- > >>>> 2 files changed, 28 insertions(+), 1 deletion(-) > >>>> > >>>> diff --git a/arch/x86/include/asm/perf_event.h b/arch/x86/include/asm/perf_event.h > >>>> index f6fc8dd51ef4..c848f504e467 100644 > >>>> --- a/arch/x86/include/asm/perf_event.h > >>>> +++ b/arch/x86/include/asm/perf_event.h > >>>> @@ -214,6 +214,14 @@ union cpuid_0x80000022_ebx { > >>>> unsigned int full; > >>>> }; > >>>> > >>>> +union cpuid_0x80000022_eax { > >>>> + struct { > >>>> + /* Performance Monitoring Version 2 Supported */ > >>>> + unsigned int perfmon_v2:1; > >>>> + } split; > >>>> + unsigned int full; > >>>> +}; > >>>> + > >>>> struct x86_pmu_capability { > >>>> int version; > >>>> int num_counters_gp; > >>>> diff --git a/arch/x86/kvm/cpuid.c b/arch/x86/kvm/cpuid.c > >>>> index 75dcf7a72605..08a29ab096d2 100644 > >>>> --- a/arch/x86/kvm/cpuid.c > >>>> +++ b/arch/x86/kvm/cpuid.c > >>>> @@ -1094,7 +1094,7 @@ static inline int __do_cpuid_func(struct kvm_cpuid_array *array, u32 function) > >>>> entry->edx = 0; > >>>> break; > >>>> case 0x80000000: > >>>> - entry->eax = min(entry->eax, 0x80000021); > >>>> + entry->eax = min(entry->eax, 0x80000022); > >>>> /* > >>>> * Serializing LFENCE is reported in a multitude of ways, and > >>>> * NullSegClearsBase is not reported in CPUID on Zen2; help > >>>> @@ -1203,6 +1203,25 @@ static inline int __do_cpuid_func(struct kvm_cpuid_array *array, u32 function) > >>>> if (!static_cpu_has_bug(X86_BUG_NULL_SEG)) > >>>> entry->eax |= BIT(6); > >>>> break; > >>>> + /* AMD Extended Performance Monitoring and Debug */ > >>>> + case 0x80000022: { > >>>> + union cpuid_0x80000022_eax eax; > >>>> + union cpuid_0x80000022_ebx ebx; > >>>> + > >>>> + entry->eax = entry->ebx = entry->ecx = entry->edx = 0; > >>>> + if (!enable_pmu) > >>>> + break; > >>>> + > >>>> + if (kvm_pmu_cap.version > 1) { > >>>> + /* AMD PerfMon is only supported up to V2 in the KVM. */ > >>>> + eax.split.perfmon_v2 = 1; > >>>> + ebx.split.num_core_pmc = min(kvm_pmu_cap.num_counters_gp, > >>>> + KVM_AMD_PMC_MAX_GENERIC); > >>> > >>> Note that the number of core PMCs has to be at least 6 if > >>> guest_cpuid_has(vcpu, X86_FEATURE_PERFCTR_CORE). I suppose this leaf > >>> could claim fewer, but the first 6 PMCs must work, per the v1 PMU > >>> spec. That is, software that knows about PERFCTR_CORE, but not about > >>> PMU v2, can rightfully expect 6 PMCs. > >> > >> I thought the NumCorePmc number would only make sense if > >> CPUID.80000022.eax.perfmon_v2 > >> bit was present, but considering that the user space is perfectly fine with just > >> configuring the > >> NumCorePmc number without setting perfmon_v2 bit at all, so how about: > > > > CPUID.80000022H might only make sense if X86_FEATURE_PERFCTR_CORE is > > present. It's hard to know in the absence of documentation. > > Whenever this happens, we may always leave the definition of behavior to the > hypervisor. I disagree. If CPUID.0H reports "AuthenticAMD," then AMD is the sole authority on behavior. > > > >> /* AMD Extended Performance Monitoring and Debug */ > >> case 0x80000022: { > >> union cpuid_0x80000022_eax eax; > >> union cpuid_0x80000022_ebx ebx; > >> bool perfctr_core; > >> > >> entry->eax = entry->ebx = entry->ecx = entry->edx = 0; > >> if (!enable_pmu) > >> break; > >> > >> perfctr_core = kvm_cpu_cap_has(X86_FEATURE_PERFCTR_CORE); > >> if (!perfctr_core) > >> ebx.split.num_core_pmc = AMD64_NUM_COUNTERS; > >> if (kvm_pmu_cap.version > 1) { > >> /* AMD PerfMon is only supported up to V2 in the KVM. */ > >> eax.split.perfmon_v2 = 1; > >> ebx.split.num_core_pmc = min(kvm_pmu_cap.num_counters_gp, > >> KVM_AMD_PMC_MAX_GENERIC); > >> } > >> if (perfctr_core) { > >> ebx.split.num_core_pmc = max(ebx.split.num_core_pmc, > >> AMD64_NUM_COUNTERS_CORE); > >> } > > > > This still isn't quite right. All AMD CPUs must support a minimum of 4 PMCs. > > K7 at least. I could not confirm that all antique AMD CPUs have 4 counters w/o > perfctr_core. The APM says, "All implementations support the base set of four performance counter / event-select pairs." That is unequivocal. > > > >> > >> entry->eax = eax.full; > >> entry->ebx = ebx.full; > >> break; > >> } > >> > >> ? > >> > >> Once 0x80000022 appears, ebx.split.num_core_pmc will report only > >> the real "Number of Core Performance Counters" regardless of perfmon_v2. > >> > >>> > >>> > >>>> + } > >>>> + entry->eax = eax.full; > >>>> + entry->ebx = ebx.full; > >>>> + break; > >>>> + } > >>>> /*Add support for Centaur's CPUID instruction*/ > >>>> case 0xC0000000: > >>>> /*Just support up to 0xC0000004 now*/ > >>>> -- > >>>> 2.37.3 > >>>>