From mboxrd@z Thu Jan  1 00:00:00 1970
From: =?UTF-8?Q?Roger_Pau_Monn=c3=a9?= <roger.pau@citrix.com>
Subject: Re: [PATCH v6 24/29] xen/x86: allow HVM guests to use
 hypercalls to bring up vCPUs
Date: Wed, 30 Sep 2015 16:23:01 +0200
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To: Jan Beulich <JBeulich@suse.com>
Cc: Ian Campbell <ian.campbell@citrix.com>, George Dunlap <George.Dunlap@eu.citrix.com>, Andrew Cooper <andrew.cooper3@citrix.com>, Tim Deegan <tim@xen.org>, Stefano Stabellini <stefano.stabellini@citrix.com>, xen-devel@lists.xenproject.org
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El 30/09/15 a les 14.35, Jan Beulich ha escrit:
> On 30.09.15 at 14:19, <roger.pau@citrix.com> wrote:
>> For VCPU_HVM_MODE_32B:
>>  - rIP within CS limit.
>>  - Check that CS.DPL == SS.DPL.
>>  - rSP within SS limit.
>>
>> TBH I don't think we should enforce the last two checks, starting with
>> an invalid stack should be fine as long as the user knows it. Maybe
>> print a warning/debug message in this case?
> 
> I wouldn't check ESP at all. As to the two DPLs to, I don't think you
> could launch a guest with these disagreeing.

I think we should basically check that the DPL of the CS segment is
equal or greater than the DPL of all the other segments (ds, ss and es).

Roger.