Re: [Xen-devel] [RFC 3/4] HVM x86 deprivileged mode: Code for switching into/out of deprivileged mode

[Ben Catterall <Ben.Catterall@xxxxxxxxxx>]

On 17/08/15 16:17, Jan Beulich wrote:
> > > > On 17.08.15 at 17:07, <tim@xxxxxxx> wrote:
> > At 14:53 +0100 on 17 Aug (1439823232), Ben Catterall wrote:
> > > So, have we arrived at a decision for this? Thanks!
> > Seems to have stalled a bit.  OK, I propose that:
> >   - we use TR/IST to make Xen take interrupts/exceptions at a different SP;
> >   - we make that SP be an extension of the main stack, so that things
> >     like current() Just Work[tm];
From Xen's cpu stack layout, page 4 is currently unused so I'll put it 
here. Is this an acceptable?
> >   - we set this up and tear it down when we enter/leave depriv mode.
> >   - someone ought to look at the case where IST handlers copy
> >     themselves to the main stack, and see if we need to adjust that too.
> >
> > Any other proposals?
> No.

> > I think we can leave the question of TR switching on VMEXIT as a
> > separate issue.
> Just like for the other one - at this point I think anything that work
> should be okay. Dealing with quirks can be deferred (but it would
> be nice if a respective note was added in a prominent place so it
> doesn't get forgotten once/if these patches leave RFC state).
>
> Jan
Ok, thanks all!

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