Re: arm: alloc_heap_pages allocates already allocated page

[Vijay Kilari <vijay.kilari@gmail.com>]

On Tue, Feb 7, 2017 at 3:37 PM, Julien Grall <julien.grall@arm.com> wrote:
> On 07/02/2017 08:18, Vijay Kilari wrote:
>>
>> Hi,
>
>
> Hello,
>
>>    I am seeing below panic with NUMA during DT mappings in
>> alloc_heap_pages()
>> BUG_ON(pg[i].count_info != PGC_state_free);
>> However, this issue is not there with 4.7 version. The same NUMA board
>> boots fine.
>
>
> I am a bit confused by what you are saying. Xen on ARM does not yet support
> NUMA. I also know you are working on NUMA support. So does the BUG happen on
> upstream xen or upstream xen + your patches?

I was testing with Andre ITS patches (RFC version 1) + my NUMA patches
+ upstream xen.
However now I tested with upstream xen + Andre ITS patches (staging
branch) on NUMA board.
I see panic (similar to what I see with my patches). Log are here.

http://pastebin.com/QJqUBvD9

The same plain upstream xen + Andre ITS patches boots fine with non-NUMA board.

>
> If the latter please provide more details on your modifications.
>
>> With 4.8 or staging I see below panic.
>
>
> I would recommend you to try bisecting to see if you can pin point a
> specific commit.
>
>>
>> I have add print in alloc_heap_pages to print page_to_mfn(pg) and
>> before and after calling
>> map_range_to_domain() DT mapping.
>> It shows that 0x83e22a is returned for multiple alloc_heap_page requests.
>
>
> This is fine as long as there is a free_heap_pages between the 2 calls of
> alloc_heap_pages. I would recommend you to look if free_heap_pages has been
> called.
>
> [....]
>
>
>> (XEN) Xen BUG at page_alloc.c:870
>
>
> I was not able to spot a BUG at line 870 but 827. I think, the
> BUG_ON(PGC_state_free) is here to catch potential bug in the allocator, all
> the pages allocated should always be free.
>
> Furthermore, we haven't made much changes in page_alloc.c recently. So this
> 43 lines differences made me wonder if you did other changes than adding
> debug?

Yes, I added debug prints.

>
> Regards,
>
> --
> Julien Grall

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