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Re: [Xen-devel][RFC] Dynamic modes support for PV xenfb (included)

To: Pat Campbell <plc@xxxxxxxxxx>
Subject: Re: [Xen-devel][RFC] Dynamic modes support for PV xenfb (included)
From: Gerd Hoffmann <kraxel@xxxxxxxxxx>
Date: Thu, 31 Jan 2008 09:22:40 +0100
Cc: Derek Murray <Derek.Murray@xxxxxxxxxxxx>, "xen-devel@xxxxxxxxxxxxxxxxxxx" <xen-devel@xxxxxxxxxxxxxxxxxxx>, "Daniel P. Berrange" <berrange@xxxxxxxxxx>, Markus Armbruster <armbru@xxxxxxxxxx>
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Pat Campbell wrote:
> Markus Armbruster wrote:
>> I can't see how using grants for the page directory is an improvement
>> over your previous iteration, which used pd[].  Can you explain?
>>   
> I will try, I am not the greatest communicator lately. 

The real question is why stop half-way with the grant tables conversion?
You should put grant references instead of mfns into the page list
pages, i.e. map the framebuffer itself using grants too.  That will kill
even more 32/64 bit differences btw.

> While I was working on this I "briefly" looked at the grant APIs to see
> how hard it would be to create a new API that allocates and claims a
> continuous block of references.

You don't need that.  xc_gnttab_map_grant_refs() takes a list of grant
refs and creates a linear mapping of those for you.

Only problem is that gntdev has a 128 grants limit, this needs fixing.
Derek?

cheers,
  Gerd

-- 
http://kraxel.fedorapeople.org/xenner/

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