Re: [kvm-devel] [PATCH] export notifier #1

[Benjamin Herrenschmidt]

On Tue, 2008-01-22 at 12:34 -0800, Christoph Lameter wrote:
> 
> - Notifiers are called *after* we tore down ptes. At that point pages
>   may already have been freed and reused. This means that there can
>   still be uses of the page by the user of mmu_ops after the OS has
>   dropped its mapping. IMHO the foreign entity needs to drop its
>   mappings first. That also ensures that the entities operated
>   upon continue to exist.

That's definitely an issue. Maybe having the foreign entity get a
reference to the page and drop it when it unmaps would help ?

> - anon_vma/inode and pte locks are held during callbacks.

So how does that fix the problem of sleeping then ?

Ben.


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