Re: [PATCH V7 08/18] x86/entry: Preserve PKRS MSR across exceptions

[Andy Lutomirski]

On 11/12/21 16:50, Ira Weiny wrote:
> On Tue, Aug 03, 2021 at 09:32:21PM -0700, 'Ira Weiny' wrote:
> > From: Ira Weiny <ira.weiny@xxxxxxxxx>
> >
> > The PKRS MSR is not managed by XSAVE.  It is preserved through a context
> > switch but this support leaves exception handling code open to memory
> > accesses during exceptions.
> >
> > 2 possible places for preserving this state were considered,
> > irqentry_state_t or pt_regs.[1]  pt_regs was much more complicated and
> > was potentially fraught with unintended consequences.[2]  However, Andy
> > came up with a way to hide additional values on the stack which could be
> > accessed as "extended_pt_regs".[3]
>
> Andy,
>
> I'm preparing to send V8 of this PKS work.  But I have not seen any feed back
> since I originally implemented this in V4[1].
>
> Does this meets your expectations?  Are there any issues you can see with this
> code?

I think I'm generally okay with the approach to allocating space.  All 
of Thomas' comments still apply, though.  (Sorry, I'm horribly behind.)