Re: [PATCH v6 11/10] x86/retpoline: Avoid return buffer underflows on context switch II

[Andi Kleen]

> > On Skylake and Broadwell when the RSB underflows it will fall back to the 
> > indirect branch predictor, which can be poisoned and we try to avoid
> > using with retpoline. So we try to avoid underflows, and this filling
> > helps us with that.
> 
> That's no longer true for Broadwell with the latest microcode, right?

That's right.

-Andi