Message-ID: <45D26797.5090600@goop.org>
Date: Tue, 13 Feb 2007 17:36:23 -0800
From: Jeremy Fitzhardinge <jeremy@goop.org>
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To: Dan Hecht <dhecht@vmware.com>
CC: Andi Kleen <ak@muc.de>, Andrew Morton <akpm@osdl.org>,
       virtualization@lists.osdl.org, xen-devel@lists.xensource.com,
       Chris Wright <chrisw@sous-sol.org>, linux-kernel@vger.kernel.org
Subject: Re: [patch 05/21] Xen-paravirt: paravirt_ops: allocate a fixmap slot
References: <20070213221729.772002682@goop.org> <20070213221829.845132535@goop.org> <45D2649D.4080508@vmware.com>
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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.

    J
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