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

[Dan Magenheimer <dan.magenheimer@xxxxxxxxxx>]

Hmm... it looks like steal_page() only works one way,
from owned-by-d to anonymous, true?  I need the
other direction as well.  Other than that, the
only difference I see is that page->count_info
is being cleared/set in a cmpxchg loop; I assume
this is because multiple domains might be contending
to use/unuse the page?  I wonder if I need that
given that in my case the page is never addressed by
any domain, just used inside the hypervisor, and
the owned-by-d is mostly for accounting purposes.

> 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?

Thanks,
Dan

> -----Original Message-----
> From: Keir Fraser [mailto:keir.fraser@xxxxxxxxxxxxx]
> Sent: Friday, February 13, 2009 1:54 AM
> To: Dan Magenheimer; Xen-Devel (E-mail)
> Subject: Re: [Xen-devel] RE: transferring ownership of domheap pages
> 
> 
> Yeah, that's pretty... optimistic. ;-) Use steal_page() plus 
> whatever bits
> of gnttab_transfer() you think you might need. If you can 
> cleanly abstract
> that into a common function all the better, but you probably 
> won't need much
> code in addition to steal_page() anyway.
> 
>  -- Keir
> 
> On 13/02/2009 03:37, "Dan Magenheimer" 
> <dan.magenheimer@xxxxxxxxxx> wrote:
> 
> > Here's a first cut.  Works only from anon to non-anon
> > or non-anon to anon (not non-anon1 to non-anon2).
> > 
> >> -----Original Message-----
> >> From: Dan Magenheimer
> >> Sent: Thursday, February 12, 2009 5:59 PM
> >> To: Xen-Devel (E-mail)
> >> Subject: transferring ownership of domheap pages
> >> 
> >> 
> >> I'd like to have routines to transfer ownership
> >> of a page both from domain D1 to anonymous and
> >> from anonymous to domain D2, without the necessity
> >> of doing a free_domheap_pages followed by an
> >> alloc_domheap_pages (primarily because I don't
> >> want to scrub the page as I know it will be
> >> immediately overwritten by the new owner).
> >> The anon-to-D2 would fail (return NULL) if
> >> D2 is fully allocated.
> >> 
> >> Any problems to watch out for?
> >> 
> >> Thanks,
> >> Dan
> >> 
> >> P.S. Only has to work on 64-bit Xen if that matters.
> >> 
> 
> 
>

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