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Re: [Xen-devel] dma_alloc_coherent issue with tg3 in x86_64 build

To: "Ian Pratt" <m+Ian.Pratt@xxxxxxxxxxxx>
Subject: Re: [Xen-devel] dma_alloc_coherent issue with tg3 in x86_64 build
From: Keir Fraser <Keir.Fraser@xxxxxxxxxxxx>
Date: Fri, 29 Jul 2005 11:07:02 +0100
Cc: Chris Wright <chrisw@xxxxxxxx>, xen-devel@xxxxxxxxxxxxxxxxxxx, Scott Parish <srparish@xxxxxxxxxx>
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On 28 Jul 2005, at 22:25, Ian Pratt wrote:

I'm surprised that the mfns are already fragmented that early in boot.
Or maybe this case is just an example of bad luck?

debug builds go out of their way to fragment things -- its proved useful for catching drivers that are taking liberties. Maybe not too smart when
used in conjunction with dom0 grabbing all of memory...

It would be good to confirm that things are OK with non debug builds,
but I still don't think it's a good idea to rely on this. Let's hold a
couple of MB back from dom0 to avoid problems.

It only reverses the page order in domain0 -- so debug build should have no worse behaviour (Xen ought to merge the reversed pages together when domain0 frees the previously-mapped pages).

 -- Keir

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