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Date: Sun, 08 Jul 2007 23:22:20 -0700
From: Jeremy Fitzhardinge <jeremy@goop.org>
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To: Jeremy Maitin-Shepard <jbms@cmu.edu>
CC: Nick Piggin <nickpiggin@yahoo.com.au>, Al Boldi <a1426z@gawab.com>,
       linux-kernel@vger.kernel.org, Andrew Morton <akpm@linux-foundation.org>
Subject: Re: Hibernation Redesign
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Jeremy Maitin-Shepard wrote:
> It would indeed be a pain for the new kernel to be loaded and have to
> use discontiguous memory.  The trick is, though, that this is not
> necessary.  Immediately before jumping to the new kernel, the first X
> bytes (where X is the amount of memory the new kernel will get,
> typically 16MB or 64MB) of physical memory are backed up into the
> arbitrary discontiguous pages that are made available.  This will not
> take very long, because copying even 64MB of memory is extremely fast.
> Then the new kernel is free to use the first X bytes of contiguous
> physical memory.  Problem solved.
>   

You could also use the paravirt_ops pte hooks to create a mapping from 
linear "physical" addresses to actual machine pages.  This is what a Xen 
kernel needs to do, and all the infrastructure will be in place shortly.

    J