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Re: [Xen-devel] xenheap pages mapped by dom0

To: George Dunlap <George.Dunlap@xxxxxxxxxxxxx>, Jan Beulich <JBeulich@xxxxxxxxxx>
Subject: Re: [Xen-devel] xenheap pages mapped by dom0
From: Keir Fraser <keir.fraser@xxxxxxxxxxxxx>
Date: Fri, 18 Dec 2009 16:40:37 +0000
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On 18/12/2009 16:19, "George Dunlap" <George.Dunlap@xxxxxxxxxxxxx> wrote:

> However, that brings up another point: suppose that I do several
> allocations, one per cpu, and one fails.  Now I want to go and free the
> buffers I've just allocated (which shouldn't be mapped in dom0 yet).
> Can I not just call free_xenheap_pages()? Do I need to clear
> PGC_allocated before calling?

Once you have called share_xen_page_with_guest(), dom0 can map that page at
any time and it is not safe to free_xenheap_page() without first checking
for guest mappings.

Perhaps you can lazily adjust tarce buffers downwards in size? I.e. Have a
go, remember if you fail, and try again on future buffer-adjustment

> Is any of this stuff written down somewhere? :-)

No. :-)

 -- Keir

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