Re: [RFC] #MC mess

From: Steven Rostedt
Date: Wed Feb 19 2020 - 09:21:19 EST

On Wed, 19 Feb 2020 09:15:41 +0100
Peter Zijlstra <peterz@xxxxxxxxxxxxx> wrote:

> >
> > Tony, etc, can you ask your Intel contacts who care about this kind of
> > thing to stop twiddling their thumbs and FIX IT? The easy fix is
> > utterly trivial. Add a new instruction IRET_NON_NMI. It does
> > *exactly* the same thing as IRET except that it does not unmask NMIs.
> > (It also doesn't unmask NMIs if it faults.) No fancy design work.
> > Future improvements can still happen on top of this.
> Yes please! Of course, we're stuck with the existing NMI entry crap
> forever because legacy, but it would make all things NMI so much saner.

What would be nice is to have a NMI_IRET, that is defined as something
that wont break legacy CPUs. Where it could be just a nop iret, or maybe
if possible a "lock iret"? That is, not have a IRET_NON_NMI, as that
would be all over the place, but just the iret for NMI itself. As
that's in one place.

-- Steve