From mboxrd@z Thu Jan  1 00:00:00 1970
From: Ben Catterall <Ben.Catterall@citrix.com>
Subject: Re: [RFC 3/4] HVM x86 deprivileged mode: Code for
 switching into/out of deprivileged mode
Date: Tue, 18 Aug 2015 11:25:42 +0100
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To: Jan Beulich <JBeulich@suse.com>, Tim Deegan <tim@xen.org>
Cc: xen-devel@lists.xensource.com, keir@xen.org, ian.campbell@citrix.com, george.dunlap@eu.citrix.com, Andrew Cooper <andrew.cooper3@citrix.com>, Aravind Gopalakrishnan <Aravind.Gopalakrishnan@amd.com>, Suravee Suthikulpanit <suravee.suthikulpanit@amd.com>, Boris Ostrovsky <boris.ostrovsky@oracle.com>
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On 17/08/15 16:17, Jan Beulich wrote:
>>>> On 17.08.15 at 17:07, <tim@xen.org> 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!