From mboxrd@z Thu Jan  1 00:00:00 1970
From: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Subject: Re: Xen dom0 crash: "d0:v0: unhandled page	fault
	(ec=0000)"
Date: Mon, 1 Nov 2010 13:46:02 -0400
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To: Jeremy Fitzhardinge <jeremy@goop.org>
Cc: "Alan J. Wylie" <NDA5OWUy@wylie.me.uk>, "xen-devel@lists.xensource.com" <xen-devel@lists.xensource.com>, Gianni Tedesco <gianni.tedesco@citrix.com>, Stefan Kuhne <stefan.kuhne@gmx.net>, sven <ml@infinitumb.de>, Andreas Kinzler <ml-xen-devel@hfp.de>
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On Mon, Nov 01, 2010 at 01:39:40PM -0400, Konrad Rzeszutek Wilk wrote:
> > >> http://pastebin.com/3m0DpDdW - 2.6.32.24-gd0054d6-dirty - broken
> .. snip..
> > The way is this is supposed to work is:
> > 
> >    1. Xen gives the domain N pages
> >    2. There's an E820 which describes M pages (M > N)
> >    3. The kernel traverses the existing E820 and finds holes and adds
> >       the memory to a new E820_RAM region beyond M
> >    4. Set up P2M for pages up to N
> >    5. When the kernel maps all "RAM", the region from N-M is not
> >       present, and has no valid P2M mapping; in that case, xen_make_pte
> >       will return a non-present pte.
> 
> Right, and somehow his machine/kernel is not doing this. His 'N' ends up being 'M' so
> the region N-M is added to the "RAM", and xen_make_pte I _think_ returns a non-present pte
> (or maybe it does present a present pte?) In the previous kernel (2.6.32.18), it
> does exactly what you described.

Not that I am actually sure what is causing this. The interesting part is that
he sees this twice:

[    0.000000] last_pfn = 0x2d0699 max_arch_pfn = 0x400000000
[    0.000000] last_pfn = 0x2f000 max_arch_pfn = 0x400000000

And he mentioned on IRC to me that this was not due to any debugging patches.