RE: [Xen-devel] privileged op emulation

["Petersson, Mats" <Mats.Petersson@xxxxxxx>]

[snip]
> > 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]. 

--
Mats


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