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Re: [Xen-devel] Xen-unstable panic: FATAL PAGE FAULT

To: MaoXiaoyun <tinnycloud@xxxxxxxxxxx>, xen devel <xen-devel@xxxxxxxxxxxxxxxxxxx>
Subject: Re: [Xen-devel] Xen-unstable panic: FATAL PAGE FAULT
From: Keir Fraser <keir.fraser@xxxxxxxxxxxxx>
Date: Tue, 31 Aug 2010 16:00:35 +0100
Cc: Jan Beulich <JBeulich@xxxxxxxxxx>
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On 31/08/2010 15:49, "Keir Fraser" <keir.fraser@xxxxxxxxxxxxx> wrote:

> I'm cc'ing Jan to see what we can get away with in doing arithmetic on
> page_info pointers. What's the guaranteed smallest aligned contiguous ranges
> of mfn in the frame_table now, Jan? (i.e., ranges in which adjacent
> page_info structs relate to adjacent MFNs)
> If this is the problem I'm pretty sure we can come up with a patch quite
> easily, but depending on the answer to my above question to Jan, we may need
> to do some code auditing.

Actually I think we get away with it if it is guaranteed that:
pfn_pdx_bottom_mask >= (1<<MAX_ORDER)-1

I don't see that this is guaranteed by pfn_pdx_hole_setup() but it would be
easy to do, have no real harm on the technique's space saving, and I think
then all of our existing page_info pointer arithmetic would be guaranteed to
just work as it always has done.

Anyway, need to know if you have the line about "PFN compression" in your
'xm dmesg' boot output.

 -- Keir

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