On Wed, Jan 2, 2019 at 11:55 PM Wei Wang <wei.w.wang@xxxxxxxxx> wrote: > Right, thanks. Probably better to change it to below: > > msr_info->data = 0; > data = native_read_msr(MSR_IA32_PERF_CAPABILITIES); > if (vcpu->kvm->arch.lbr_in_guest) > msr_info->data |= (data & X86_PERF_CAP_MASK_LBR_FMT); > This still breaks backwards compatibility. Returning 0 and raising #GP are not the same.
