> I don't understand a word of that. > > Who cares if the LBR MSRs are touched; the guest expects up-to-date > values when it does reads them.
This is for only when the LBRs are disabled in the guest. It doesn't make sense to constantly save/restore disabled LBRs, which would be a large overhead for guests that don't use LBRs. When the LBRs are enabled they always need to be saved/restored as you say. -Andi
