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RE: [Xen-devel] privileged op emulation

  • To: "Altobelli, David" <david.altobelli@xxxxxx>, xen-devel@xxxxxxxxxxxxxxxxxxx
  • From: "Petersson, Mats" <Mats.Petersson@xxxxxxx>
  • Date: Fri, 2 Jun 2006 17:51:13 +0200
  • Delivery-date: Fri, 02 Jun 2006 08:51:52 -0700
  • List-id: Xen developer discussion <xen-devel.lists.xensource.com>
  • Thread-index: AcaGVcirZkmiH66VSJWdIi8egxxUqQAAG1UQAADFIOAAAJYsoA==
  • Thread-topic: [Xen-devel] privileged op emulation

> > Are you in this particular case thinking of "weird" side 
> effects like 
> > the OUT instruction is actually causing a SMI, in which the 
> > user-registers are being used for arguments?
> Yes, that's exactly the case I'm thinking about.  I have a 
> userspace application that basically does:
> iopl()
> ...
> Setup registers
> cli
> out -> trigger SMI which looks at registers ...
I think the CORRECT way to solve this is to have a particular port(set)
(administered by the system administrator in the form of a command-line
parameter to the Xen kernel perhaps) be allowed as "direct access" from
the user-mode kernel, so that you get the correct behaviour. Most
anything else would be somewhat wrong in one way or another
[stack-pointer, instruction pointer at the very least would be wrong]. 


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