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

To: Jan Beulich <JBeulich@xxxxxxxxxx>
Subject: Re: [Xen-devel] Xen-unstable panic: FATAL PAGE FAULT
From: Keir Fraser <keir.fraser@xxxxxxxxxxxxx>
Date: Tue, 31 Aug 2010 17:01:07 +0100
Cc: MaoXiaoyun <tinnycloud@xxxxxxxxxxx>, xen devel <xen-devel@xxxxxxxxxxxxxxxxxxx>
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On 31/08/2010 16:07, "Jan Beulich" <JBeulich@xxxxxxxxxx> wrote:

>>>> On 31.08.10 at 16:49, 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)
> Any range of struct page_info-s that crosses a 2Mb boundary is
> unsafe to make assumptions upon

Where is even that constraint ensured in the code? I can't see it (I would
have assumed that pfn_pdx_hole_setup() would be ensuring it).

 -- Keir

> (with 32-byte struct page_info
> that means 256Mb of memory, but if struct page_info grows that
> range might shrink). If that limit is too low, we might need to
> enforce a lower limit on the bit positions on which compression
> may be done (possibly at the price of doing less compression).

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