Re: [Xen-devel] [PATCH v3] xen/mm: Fix page_list_* helpers to evaluate all their arguments

[Andrew Cooper <andrew.cooper3@xxxxxxxxxx>]

On 08/03/16 09:57, Jan Beulich wrote:
>>>> On 07.03.16 at 19:12, <andrew.cooper3@xxxxxxxxxx> wrote:
>> --- a/xen/include/asm-arm/domain.h
>> +++ b/xen/include/asm-arm/domain.h
>> @@ -65,6 +65,7 @@ struct arch_domain
>>          RELMEM_mapping,
>>          RELMEM_done,
>>      } relmem;
>> +    struct page_list_head relmem_list;
> Well, if I was ARM maintainer I would say no to this otherwise pointless
> addition (even more so that this list doesn't get initialized anywhere).
> The expectation I had for how the build issue would be fixed was to
> simply not convert (at least) page_list_del2() to an inline function.

No.  Discarding parameters is what got us into the first mess.  I will
not propagate the problem.

It is a bug that ARM relied on the discarded parameters to compile.

Ultimately, the bug is that common/page_alloc.c references d->arch. 
More generally, the problem is that common/page_alloc.c has x86
specifics in it.

The two options are to make relmem_list common, or to remove x86
specifics from common by introduce arch_free_domheap_page() helpers
which maintain relmem_list on x86.  On second thoughts, this latter
option seems to be better, as it would also allow the removal of
page_list_del2, although it is not clear if this is safe to do.

~Andrew

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