[Lguest] [PATCH 3/5] lguest: avoid accidental recycling of pgdir pages
Jeremy Fitzhardinge
jeremy at goop.org
Sat Mar 28 03:28:12 EST 2009
Rusty Russell wrote:
>> 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?
>
Yes, but when you get a tlb flush hypercall, couldn't you also look up
the corresponding shadow pte and zap it so that it will get repopulated
next time around? And a full tlb flush would just zap the entire
shadow. After all, the shadow pagetable is just a glorified
software-managed tlb...
J
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