Hi Reiji, On Sun, Feb 13, 2022 at 10:57:29PM -0800, 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 > expose 0x0 (PMU is not implemented) instead. > > Change cpuid_feature_cap_perfmon_field() to update the field value > to 0x0 when it is 0xf. Definitely agree with the change in this patch. Do we need to tolerate writes of 0xf for ABI compatibility (even if it is nonsensical)? Otherwise a guest with IMP_DEF PMU cannot be migrated to a newer kernel. -- Thanks, Oliver
