Re: [PATCH v7 10/12] KVM/x86/lbr: lazy save the guest lbr stack

[Andi Kleen]

> 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