Re: [Xen-devel] [PATCH] This patch fixes several issues related to vmxassist

[Keir Fraser <Keir.Fraser@xxxxxxxxxxxx>]

On 1 Apr 2006, at 16:51, Li, Xin B wrote:

> > Yes, I'll push this one: I like the extra sanity checking. Why are the
> > checks for zero and greater-than-gdt-limit required (why is it
> > insufficient to merely check the current mode)?
> You got it :-), and I also suspect they are not required.
> I just keep it there and seems it's not harmful, when we are sure they
> are not needed, we can remove it.
I still think using and maintaining shadow segment state would 
ultimately be the correct solution. But it sounds like I was mistaken 
about how big real mode works -- I didn't realise writing a segment 
register in real mode doesn't update the hidden segment limit register 
and that's the trick that creates big real mode. That given, the 
current approach isn't so bad (there's already an acceptable kludge in 
there to deal with 'stale' hidden base addresses when switching 
protected-to-real mode) and perhaps we'll get away with leaving the 
code alone now. It's obviously a pain to revalidate it on a wide range 
of systems if we start making bigger and more fundamental changes to 
it. Also, I trust that Leendert knows rather more about the transitory 
real/protected modes than I do. :-)
 -- Keir


_______________________________________________
Xen-devel mailing list
Xen-devel@xxxxxxxxxxxxxxxxxxx
http://lists.xensource.com/xen-devel