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xen-devel
Re: [Xen-devel] Re: [patch 05/21] Xen-paravirt: paravirt_ops: allocate a
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To: |
Jan Beulich <jbeulich@xxxxxxxxxx> |
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Subject: |
Re: [Xen-devel] Re: [patch 05/21] Xen-paravirt: paravirt_ops: allocate a fixmap slot |
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From: |
Andi Kleen <ak@xxxxxx> |
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Date: |
14 Feb 2007 10:15:04 +0100 |
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Date: |
Wed, 14 Feb 2007 10:15:04 +0100 |
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Cc: |
Andrew Morton <akpm@xxxxxxxx>, Jeremy Fitzhardinge <jeremy@xxxxxxxx>, xen-devel@xxxxxxxxxxxxxxxxxxx, Dan Hecht <dhecht@xxxxxxxxxx>, linux-kernel@xxxxxxxxxxxxxxx, Chris Wright <chrisw@xxxxxxxxxxxx>, virtualization@xxxxxxxxxxxxxx |
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Wed, 14 Feb 2007 01:14:54 -0800 |
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On Wed, Feb 14, 2007 at 08:37:26AM +0000, Jan Beulich wrote:
> >>> Jeremy Fitzhardinge <jeremy@xxxxxxxx> 14.02.07 02:36 >>>
> >Dan Hecht wrote:
> >> Why doesn't Xen allocate the shared_info page from the pseudo-physical
> >> space? Doesn't it already have to steal pages from the
> >> pseudo-physical space for e.g. initial page tables, console, etc? Why
> >> not do the same for shared_info, and then you don't need a reserve the
> >> fixmap slot.
> >
> >Unlike the pagetable pages or the console page, the shared info page
> >doesn't have a pseudo-physical address, so in order to map it we need to
> >directly construct a pte containing the mfn for that page. Inserting
> >this mapping into the fixmap space seems like the easiest way to do
> >this. It's not like a fixmap slot costs anything.
>
> Otoh there are many fixmap slots not used under Xen, perhaps it would
> be possible to use one of those... One slot certainly doesn't cost a lot,
I don't have a problem with reserving one page for this.
-Andi
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