> >+#ifdef CONFIG_X86_64 > > is this #ifdeffery neccesary? Yes, otherwise build fails on 32 bit. > > I assume kvm_cpu_cap_has(X86_FEATURE_FRED) is always false > for !CONFIG_X86_64. > Looks most of FRED changes in core kernel don't have such #ifdeffery. Because it's not a compile time false, instead false from runtime. > > >+ /* Per-CPU FRED MSRs */ > > Please explain why these six MSRs are updated here and why only they are updated in > this comment. The explanation is kind of implicit "per-CPU", I will make it more explicit. Thanks! Xin