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

[Keir Fraser <keir.fraser@xxxxxxxxxxxxx>]

On 31/08/2010 17:35, "Keir Fraser" <keir.fraser@xxxxxxxxxxxxx> wrote:

>> That's somewhat implicit: srat_parse_regions() gets passed an
>> address that is at least BOOTSTRAP_DIRECTMAP_END (i.e. 4G).
>> Thus srat_parse_regions() starts off with a mask with the lower
>> 32 bits all set (only more bits can get set subsequently). Thus
>> the earliest zero bit pfn_pdx_hole_setup() can find is bit 20
>> (due to the >> PAGE_SHIFT in the invocation). Consequently
>> the smallest chunk where arithmetic is valid really is 4Gb, not
>> 256Mb as I first wrote.
> 
> Well, that's a bit too implicit for me. How about we initialise 'j' to
> MAX_ORDER in pfn_pdx_hole_setup() with a comment about supporting page_info
> pointer arithmetic within allocatable multi-page regions?

Well I agree with your logic anyway. So I don't see that this can be the
cause of MaoXiaoyun's bug. At least not directly. But then I'm stumped as to
why the page arithmetic and checks in free_heap_pages are (apparently)
resulting in a page pointer way outside the frame-table region and actually
in the directmap region.

I think an obvious next step wpuld be to get your boot output, MaoXiaoyun.
Can you please post it? And you may as well stop your memtest if you haven't
already. If you've seen the issue on more than one machine then it certainly
isn't due to that kind of hardware failure.

 -- Keir



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