Re: x86_64: Fix double fault stack setup

[Andrew Cooper <andrew.cooper3@citrix.com>]

On 24/05/12 16:46, Jan Beulich wrote:
>>>> On 24.05.12 at 17:28, Andrew Cooper <andrew.cooper3@citrix.com> wrote:
>> Do we actually care about this error from an INT 08?
> Definitely not - the hypervisor doesn't (except in your debugging)
> ever use INT nn, and nothing else can access those gates.

Ok - I will avoid debugging in this fashion in the future.

>
>> I suppose we could check under rip for 0xcd 0x08,
> That's (from my pov) an absolute no-go for the double fault
> handler, even if the above didn't hold.
>
> Jan

Yes.  After further considering, this adds an extra fault in that the
#DF handler would not successfully return, which was being hidden in my
tests by the crash kernel.

What about the entry vector?  It would be safe to do in the case of a
real #DF, and wont really break the int08 case much more than it already is.

-- 
Andrew Cooper - Dom0 Kernel Engineer, Citrix XenServer
T: +44 (0)1223 225 900, http://www.citrix.com