On Tue, Nov 7, 2023 at 4:31 PM Sean Christopherson <seanjc@xxxxxxxxxx> wrote: > > Remove KVM's bogus restriction that the guest can't program an event whose > encoding matches an unsupported architectural event. The enumeration of > an architectural event only says that if a CPU supports an architectural > event, then the event can be programmed using the architectural encoding. > The enumeration does NOT say anything about the encoding when the CPU > doesn't report support the architectural event. > > Preventing the guest from counting events whose encoding happens to match > an architectural event breaks existing functionality whenever Intel adds > an architectural encoding that was *ever* used for a CPU that doesn't > enumerate support for the architectural event, even if the encoding is for > the exact same event! > > E.g. the architectural encoding for Top-Down Slots is 0x01a4. Broadwell > CPUs, which do not support the Top-Down Slots architectural event, 0x10a4 Nit: 0x01a4 > is a valid, model-specific event. Denying guest usage of 0x01a4 if/when > KVM adds support for Top-Down slots would break any Broadwell-based guest. > > Reported-by: Kan Liang <kan.liang@xxxxxxxxxxxxxxx> > Closes: https://lore.kernel.org/all/2004baa6-b494-462c-a11f-8104ea152c6a@xxxxxxxxxxxxxxx > Fixes: a21864486f7e ("KVM: x86/pmu: Fix available_event_types check for REF_CPU_CYCLES event") > Reviewed-by: Dapeng Mi <dapeng1.mi@xxxxxxxxxxxxxxx> > Reviewed-by: Jim Mattson <jmattson@xxxxxxxxxx> > Signed-off-by: Sean Christopherson <seanjc@xxxxxxxxxx> > --- > arch/x86/include/asm/kvm-x86-pmu-ops.h | 1 - > arch/x86/kvm/pmu.c | 1 - > arch/x86/kvm/pmu.h | 1 - > arch/x86/kvm/svm/pmu.c | 6 ---- > arch/x86/kvm/vmx/pmu_intel.c | 38 -------------------------- > 5 files changed, 47 deletions(-) > > diff --git a/arch/x86/include/asm/kvm-x86-pmu-ops.h b/arch/x86/include/asm/kvm-x86-pmu-ops.h > index 6c98f4bb4228..884af8ef7657 100644 > --- a/arch/x86/include/asm/kvm-x86-pmu-ops.h > +++ b/arch/x86/include/asm/kvm-x86-pmu-ops.h > @@ -12,7 +12,6 @@ BUILD_BUG_ON(1) > * a NULL definition, for example if "static_call_cond()" will be used > * at the call sites. > */ > -KVM_X86_PMU_OP(hw_event_available) > KVM_X86_PMU_OP(pmc_idx_to_pmc) > KVM_X86_PMU_OP(rdpmc_ecx_to_pmc) > KVM_X86_PMU_OP(msr_idx_to_pmc) > diff --git a/arch/x86/kvm/pmu.c b/arch/x86/kvm/pmu.c > index 9ae07db6f0f6..99ed72966528 100644 > --- a/arch/x86/kvm/pmu.c > +++ b/arch/x86/kvm/pmu.c > @@ -374,7 +374,6 @@ static bool check_pmu_event_filter(struct kvm_pmc *pmc) > static bool pmc_event_is_allowed(struct kvm_pmc *pmc) > { > return pmc_is_globally_enabled(pmc) && pmc_speculative_in_use(pmc) && > - static_call(kvm_x86_pmu_hw_event_available)(pmc) && > check_pmu_event_filter(pmc); > } > > diff --git a/arch/x86/kvm/pmu.h b/arch/x86/kvm/pmu.h > index 1d64113de488..10fe5bf02705 100644 > --- a/arch/x86/kvm/pmu.h > +++ b/arch/x86/kvm/pmu.h > @@ -19,7 +19,6 @@ > #define VMWARE_BACKDOOR_PMC_APPARENT_TIME 0x10002 > > struct kvm_pmu_ops { > - bool (*hw_event_available)(struct kvm_pmc *pmc); > struct kvm_pmc *(*pmc_idx_to_pmc)(struct kvm_pmu *pmu, int pmc_idx); > struct kvm_pmc *(*rdpmc_ecx_to_pmc)(struct kvm_vcpu *vcpu, > unsigned int idx, u64 *mask); > diff --git a/arch/x86/kvm/svm/pmu.c b/arch/x86/kvm/svm/pmu.c > index 373ff6a6687b..5596fe816ea8 100644 > --- a/arch/x86/kvm/svm/pmu.c > +++ b/arch/x86/kvm/svm/pmu.c > @@ -73,11 +73,6 @@ static inline struct kvm_pmc *get_gp_pmc_amd(struct kvm_pmu *pmu, u32 msr, > return amd_pmc_idx_to_pmc(pmu, idx); > } > > -static bool amd_hw_event_available(struct kvm_pmc *pmc) > -{ > - return true; > -} > - > static bool amd_is_valid_rdpmc_ecx(struct kvm_vcpu *vcpu, unsigned int idx) > { > struct kvm_pmu *pmu = vcpu_to_pmu(vcpu); > @@ -249,7 +244,6 @@ static void amd_pmu_reset(struct kvm_vcpu *vcpu) > } > > struct kvm_pmu_ops amd_pmu_ops __initdata = { > - .hw_event_available = amd_hw_event_available, > .pmc_idx_to_pmc = amd_pmc_idx_to_pmc, > .rdpmc_ecx_to_pmc = amd_rdpmc_ecx_to_pmc, > .msr_idx_to_pmc = amd_msr_idx_to_pmc, > diff --git a/arch/x86/kvm/vmx/pmu_intel.c b/arch/x86/kvm/vmx/pmu_intel.c > index c6e227edcf8e..7737ee2fc62f 100644 > --- a/arch/x86/kvm/vmx/pmu_intel.c > +++ b/arch/x86/kvm/vmx/pmu_intel.c > @@ -101,43 +101,6 @@ static struct kvm_pmc *intel_pmc_idx_to_pmc(struct kvm_pmu *pmu, int pmc_idx) > } > } > > -static bool intel_hw_event_available(struct kvm_pmc *pmc) > -{ > - struct kvm_pmu *pmu = pmc_to_pmu(pmc); > - u8 event_select = pmc->eventsel & ARCH_PERFMON_EVENTSEL_EVENT; > - u8 unit_mask = (pmc->eventsel & ARCH_PERFMON_EVENTSEL_UMASK) >> 8; > - int i; > - > - /* > - * Fixed counters are always available if KVM reaches this point. If a > - * fixed counter is unsupported in hardware or guest CPUID, KVM doesn't > - * allow the counter's corresponding MSR to be written. KVM does use > - * architectural events to program fixed counters, as the interface to > - * perf doesn't allow requesting a specific fixed counter, e.g. perf > - * may (sadly) back a guest fixed PMC with a general purposed counter. > - * But if _hardware_ doesn't support the associated event, KVM simply > - * doesn't enumerate support for the fixed counter. > - */ > - if (pmc_is_fixed(pmc)) > - return true; > - > - BUILD_BUG_ON(ARRAY_SIZE(intel_arch_events) != NR_INTEL_ARCH_EVENTS); > - > - /* > - * Disallow events reported as unavailable in guest CPUID. Note, this > - * doesn't apply to pseudo-architectural events (see above). > - */ > - for (i = 0; i < NR_REAL_INTEL_ARCH_EVENTS; i++) { > - if (intel_arch_events[i].eventsel != event_select || > - intel_arch_events[i].unit_mask != unit_mask) > - continue; > - > - return pmu->available_event_types & BIT(i); > - } > - > - return true; > -} > - > static bool intel_is_valid_rdpmc_ecx(struct kvm_vcpu *vcpu, unsigned int idx) > { > struct kvm_pmu *pmu = vcpu_to_pmu(vcpu); > @@ -802,7 +765,6 @@ void intel_pmu_cross_mapped_check(struct kvm_pmu *pmu) > } > > struct kvm_pmu_ops intel_pmu_ops __initdata = { > - .hw_event_available = intel_hw_event_available, > .pmc_idx_to_pmc = intel_pmc_idx_to_pmc, > .rdpmc_ecx_to_pmc = intel_rdpmc_ecx_to_pmc, > .msr_idx_to_pmc = intel_msr_idx_to_pmc, > -- > 2.42.0.869.gea05f2083d-goog >
