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[Xen-devel] Re: [Question] Why code differs in construct_dom0?

To: "Shan, Haitao" <haitao.shan@xxxxxxxxx>
Subject: [Xen-devel] Re: [Question] Why code differs in construct_dom0?
From: Keir Fraser <keir.fraser@xxxxxxxxxxxxx>
Date: Thu, 20 Nov 2008 13:03:01 +0000
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On 20/11/08 12:52, "Shan, Haitao" <haitao.shan@xxxxxxxxx> wrote:

> Either increasing the reservation (like 384M) or changing the initial p2m
> mapping in dom0 can solve the problem, and our tests verified this judgment.
> We do not know which solution is better. That's why we are seeking your kindly
> help.
> I am not sure if I have explained clearly enough so far. So any questions on
> the problem itself, Keir?

I don't think there's an easy answer. Increasing the default reservation
won't please everyone, since not everyone will want dom0 to be 'robbed' of
384M! It's also a bit specific to this particular situation.

Relying on p2m being roughly 1:1 is a bit gross but, if it helps, we could
change the debug code to swap adjacent pairs of pages, rather than reversing
the entire p2m map? Then it would still happen that low pseudophys addresses
have low machine addresses? It's kind of nasty though.

Perhaps really we should have the crash path in Linux print a message
advising to specify dom0_mem= to Xen?

 -- Keir



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