Re: [Xen-devel] RE: transferring ownership of domheap pages

[Keir Fraser <keir.fraser@xxxxxxxxxxxxx>]

On 13/02/2009 15:14, "Dan Magenheimer" <dan.magenheimer@xxxxxxxxxx> wrote:

>> Yeah, that's pretty... optimistic. ;-)
> 
> What else do you see that is missing in my first cut?
> Do you see any other code there that's just wrong?

You can't just assert that count_info == PGC_allocated|1, for example. You
need to be careful that mappings aren't created or destroyed while you are
changing the ownership. Steal_page() does that. Once a page is anonymous,
transferring it to a domain is easier, since mappings can't be
created/destroyed while it is anonymous. So steal_page() just does the hard
transition for you (non-anon -> anon). A benefit of using steal_page() is
that we will maintain that for other callers -- a private implementation in
tmem risks getting subtly unsafely broken every now and then.

 -- Keir



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