[Lguest] [PATCH 3/5] lguest: avoid accidental recycling of pgdir pages

[Rusty Russell]

On Friday 27 March 2009 10:47:32 Jeremy Fitzhardinge wrote:
> Rusty Russell wrote:
> > Impact: potential bugfix
> >
> > In theory, the kernel could reuse the same page as pgdir for a new process
> > while the hypervisor keeps it cached.  This would have undesirable results.
> >   
> 
> You can't just do this in tlb flush?

I don't think so.  The problem is that lguest tracks 4 toplevels, using random
replacement.  This cache is indexed by cr3 value.

Lguest assumes it's told about all pte removals or changes, but simple
additions get faulted in.  If a pgdir page gets reused we'll potentially have
stale values from its previous life as a pgdir, no?

Now, I haven't *seen* this happen...
Rusty.