Hi Eric, On Thu, Dec 2, 2021 at 2:57 AM Eric Auger <eauger@xxxxxxxxxx> wrote: > > Hi Reiji, > > On 11/30/21 6:32 AM, Reiji Watanabe wrote: > > Hi Eric, > > > > On Thu, Nov 25, 2021 at 12:30 PM Eric Auger <eauger@xxxxxxxxxx> wrote: > >> > >> Hi Reiji, > >> > >> On 11/17/21 7:43 AM, Reiji Watanabe wrote: > >>> When ID_AA64DFR0_EL1.PMUVER or ID_DFR0_EL1.PERFMON is 0xf, which > >>> means IMPLEMENTATION DEFINED PMU supported, KVM unconditionally > >>> expose the value for the guest as it is. Since KVM doesn't support > >>> IMPLEMENTATION DEFINED PMU for the guest, in that case KVM should > >>> exopse 0x0 (PMU is not implemented) instead. > >> s/exopse/expose > >>> > >>> Change cpuid_feature_cap_perfmon_field() to update the field value > >>> to 0x0 when it is 0xf. > >> is it wrong to expose the guest with a Perfmon value of 0xF? Then the > >> guest should not use it as a PMUv3? > > > >> is it wrong to expose the guest with a Perfmon value of 0xF? Then the > >> guest should not use it as a PMUv3? > > > > For the value 0xf in ID_AA64DFR0_EL1.PMUVER and ID_DFR0_EL1.PERFMON, > > Arm ARM says: > > "IMPLEMENTATION DEFINED form of performance monitors supported, > > PMUv3 not supported." > > > > Since the PMU that KVM supports for guests is PMUv3, 0xf shouldn't > > be exposed to guests (And this patch series doesn't allow userspace > > to set the fields to 0xf for guests). > What I don't get is why this isn't detected before (in kvm_reset_vcpu). > if the VCPU was initialized with KVM_ARM_VCPU_PMU_V3 can we honor this > init request if the host pmu is implementation defined? KVM_ARM_VCPU_INIT with KVM_ARM_VCPU_PMU_V3 will fail in kvm_reset_vcpu() if the host PMU is implementation defined. The AA64DFR0 and DFR0 registers for a vCPU without KVM_ARM_VCPU_PMU_V3 indicates IMPLEMENTATION DEFINED PMU support, which is not correct. Thanks, Reiji
