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

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?


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).


Ok, thanks all!

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