From 5eb849322d7f7ae9d5c587c7bc3b4f7c6872cd2f Mon Sep 17 00:00:00 2001 From: Kyle Huey Date: Mon, 2 May 2022 22:01:36 -0700 Subject: [PATCH 1/2] KVM: x86/svm: Account for family 17h event renumberings in amd_pmc_perf_hw_id Zen renumbered some of the performance counters that correspond to the well known events in perf_hw_id. This code in KVM was never updated for that, so guest that attempt to use counters on Zen that correspond to the pre-Zen perf_hw_id values will silently receive the wrong values. This has been observed in the wild with rr[0] when running in Zen 3 guests. rr uses the retired conditional branch counter 00d1 which is incorrectly recognized by KVM as PERF_COUNT_HW_STALLED_CYCLES_BACKEND. [0] https://rr-project.org/ Signed-off-by: Kyle Huey Message-Id: <20220503050136.86298-1-khuey@kylehuey.com> Cc: stable@vger.kernel.org [Check guest family, not host. - Paolo] Signed-off-by: Paolo Bonzini --- arch/x86/kvm/svm/pmu.c | 28 +++++++++++++++++++++++++--- 1 file changed, 25 insertions(+), 3 deletions(-) diff --git a/arch/x86/kvm/svm/pmu.c b/arch/x86/kvm/svm/pmu.c index 24eb935b6f85c..311cbaa0c3ddf 100644 --- a/arch/x86/kvm/svm/pmu.c +++ b/arch/x86/kvm/svm/pmu.c @@ -45,6 +45,22 @@ static struct kvm_event_hw_type_mapping amd_event_mapping[] = { [7] = { 0xd1, 0x00, PERF_COUNT_HW_STALLED_CYCLES_BACKEND }, }; +/* duplicated from amd_f17h_perfmon_event_map. */ +static struct kvm_event_hw_type_mapping amd_f17h_event_mapping[] = { + [0] = { 0x76, 0x00, PERF_COUNT_HW_CPU_CYCLES }, + [1] = { 0xc0, 0x00, PERF_COUNT_HW_INSTRUCTIONS }, + [2] = { 0x60, 0xff, PERF_COUNT_HW_CACHE_REFERENCES }, + [3] = { 0x64, 0x09, PERF_COUNT_HW_CACHE_MISSES }, + [4] = { 0xc2, 0x00, PERF_COUNT_HW_BRANCH_INSTRUCTIONS }, + [5] = { 0xc3, 0x00, PERF_COUNT_HW_BRANCH_MISSES }, + [6] = { 0x87, 0x02, PERF_COUNT_HW_STALLED_CYCLES_FRONTEND }, + [7] = { 0x87, 0x01, PERF_COUNT_HW_STALLED_CYCLES_BACKEND }, +}; + +/* amd_pmc_perf_hw_id depends on these being the same size */ +static_assert(ARRAY_SIZE(amd_event_mapping) == + ARRAY_SIZE(amd_f17h_event_mapping)); + static unsigned int get_msr_base(struct kvm_pmu *pmu, enum pmu_type type) { struct kvm_vcpu *vcpu = pmu_to_vcpu(pmu); @@ -140,6 +156,7 @@ static inline struct kvm_pmc *get_gp_pmc_amd(struct kvm_pmu *pmu, u32 msr, static unsigned int amd_pmc_perf_hw_id(struct kvm_pmc *pmc) { + struct kvm_event_hw_type_mapping *event_mapping; u8 event_select = pmc->eventsel & ARCH_PERFMON_EVENTSEL_EVENT; u8 unit_mask = (pmc->eventsel & ARCH_PERFMON_EVENTSEL_UMASK) >> 8; int i; @@ -148,15 +165,20 @@ static unsigned int amd_pmc_perf_hw_id(struct kvm_pmc *pmc) if (WARN_ON(pmc_is_fixed(pmc))) return PERF_COUNT_HW_MAX; + if (guest_cpuid_family(pmc->vcpu) >= 0x17) + event_mapping = amd_f17h_event_mapping; + else + event_mapping = amd_event_mapping; + for (i = 0; i < ARRAY_SIZE(amd_event_mapping); i++) - if (amd_event_mapping[i].eventsel == event_select - && amd_event_mapping[i].unit_mask == unit_mask) + if (event_mapping[i].eventsel == event_select + && event_mapping[i].unit_mask == unit_mask) break; if (i == ARRAY_SIZE(amd_event_mapping)) return PERF_COUNT_HW_MAX; - return amd_event_mapping[i].event_type; + return event_mapping[i].event_type; } /* check if a PMC is enabled by comparing it against global_ctrl bits. Because From 5a1bde46f98b893cda6122b00e94c0c40a6ead3c Mon Sep 17 00:00:00 2001 From: Sandipan Das Date: Wed, 27 Apr 2022 17:01:49 +0530 Subject: [PATCH 2/2] kvm: x86/cpuid: Only provide CPUID leaf 0xA if host has architectural PMU On some x86 processors, CPUID leaf 0xA provides information on Architectural Performance Monitoring features. It advertises a PMU version which Qemu uses to determine the availability of additional MSRs to manage the PMCs. Upon receiving a KVM_GET_SUPPORTED_CPUID ioctl request for the same, the kernel constructs return values based on the x86_pmu_capability irrespective of the vendor. This leaf and the additional MSRs are not supported on AMD and Hygon processors. If AMD PerfMonV2 is detected, the PMU version is set to 2 and guest startup breaks because of an attempt to access a non-existent MSR. Return zeros to avoid this. Fixes: a6c06ed1a60a ("KVM: Expose the architectural performance monitoring CPUID leaf") Reported-by: Vasant Hegde Signed-off-by: Sandipan Das Message-Id: <3fef83d9c2b2f7516e8ff50d60851f29a4bcb716.1651058600.git.sandipan.das@amd.com> Signed-off-by: Paolo Bonzini --- arch/x86/kvm/cpuid.c | 5 +++++ 1 file changed, 5 insertions(+) diff --git a/arch/x86/kvm/cpuid.c b/arch/x86/kvm/cpuid.c index b24ca7f4ed7c8..732724ea5b100 100644 --- a/arch/x86/kvm/cpuid.c +++ b/arch/x86/kvm/cpuid.c @@ -887,6 +887,11 @@ static inline int __do_cpuid_func(struct kvm_cpuid_array *array, u32 function) union cpuid10_eax eax; union cpuid10_edx edx; + if (!static_cpu_has(X86_FEATURE_ARCH_PERFMON)) { + entry->eax = entry->ebx = entry->ecx = entry->edx = 0; + break; + } + perf_get_x86_pmu_capability(&cap); /*