On Fri, Jul 16, 2021 at 04:33:36PM -0700, Jim Mattson wrote: > On Fri, Jul 16, 2021 at 1:36 AM Yang Weijiang <weijiang.yang@xxxxxxxxx> wrote: > > > > From: Like Xu <like.xu@xxxxxxxxxxxxxxx> > > > > The number of Arch LBR entries available is determined by the value > > in host MSR_ARCH_LBR_DEPTH.DEPTH. The supported LBR depth values are > > enumerated in CPUID.(EAX=01CH, ECX=0):EAX[7:0]. For each bit "n" set > > in this field, the MSR_ARCH_LBR_DEPTH.DEPTH value of "8*(n+1)" is > > supported. > > > > On a guest write to MSR_ARCH_LBR_DEPTH, all LBR entries are reset to 0. > > KVM writes guest requested value to the native ARCH_LBR_DEPTH MSR > > (this is safe because the two values will be the same) when the Arch LBR > > records MSRs are pass-through to the guest. > > > > Signed-off-by: Like Xu <like.xu@xxxxxxxxxxxxxxx> > > Signed-off-by: Yang Weijiang <weijiang.yang@xxxxxxxxx> > > It might be worth noting that KVM_SET_MSRS cannot be used to emulate a > wrmsr instruction in the guest, but maybe that's already implicit. > > Reviewed-by: Jim Mattson <jmattson@xxxxxxxxxx> Thanks Jim. Yes, guest wrmsr read/write emulation shares none-host initiated path.
