Re: [patch V9 00/39] x86/entry: Rework leftovers (was part V)

From: Peter Zijlstra
Date: Thu Jun 04 2020 - 09:36:14 EST

On Thu, Jun 04, 2020 at 03:29:26PM +0200, Paolo Bonzini wrote:
> On 04/06/20 15:25, Peter Zijlstra wrote:
> > It being enabled through IA32_DEBUGCTL instead of through DR7 means that
> > the current code doesn't disable it and this then means we can have
> > nested #DB again.
> /me bangs head on door
> > Who sodding throught this was a good idea ?! What happened to #AC that
> > SLD currently uses?
> It was per-core and (presumably) considered unfixable?

Yeah, but I don't see how changing the exception vector helps with that.
#DB is an IST, and it must be, because of that lovely MOV SS thing. #AC
has none of that, _please_ use #AC.