Re: [Xen-devel] Re: [PATCH] Xen Guest Kexec

[Keir Fraser <Keir.Fraser@xxxxxxxxxxxx>]

On 2 Mar 2006, at 16:36, Gerd Hoffmann wrote:

> > Looks like your new pagetables have a writable mapping of MFN 18c95,
> > which is the new page directory. i.e., the new p.t. set is not self
> > consistent?
> They where indeed.  Wrong usage of pte_wrprotect() :-/
> Next question: Is there some way to _clear_ the trap table?
Hehe. The interface wasn't so much designed with this in mind, but it 
can be done. Pass in an array of 256 trap_info structs, where the i'th 
struct contains:
  vector=i, flags=0, cs=0, addr=1

Note the address must be non-zero, as that otherwise marks the end of 
the list! You can put whatever non-zero value you like in that field -- 
it really doesn't matter. In fact you need to pass a list of *257* 
trap_info structs, the last of which has addr==0. :-)
The critical thing that disables the trap is flags==0: that sets the 
'dpl' for the 'trap gate' to zero so it effectively is unusable.
 -- Keir


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