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SubjectRe: [PATCH v4 2/2] RISC-V: Implement sparsemem
On 2019-08-13 10:39 a.m., Paul Walmsley wrote:
> On Tue, 13 Aug 2019, Logan Gunthorpe wrote:
>
>> On 2019-08-13 12:04 a.m., Greentime Hu wrote:
>>
>>> Every architecture with mmu defines their own pfn_valid().
>>
>> Not true. Arm64, for example just uses the generic implementation in
>> mmzone.h.
>
> arm64 seems to define their own:
>
> https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/arch/arm64/Kconfig#n899

Oh, yup. My mistake.

> https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/arch/arm64/mm/init.c#n235
>
> While there are many architectures which have their own pfn_valid();
> oddly, almost none of them set HAVE_ARCH_PFN_VALID ?

Yes, much of this is super confusing. Seems HAVE_ARCH_PFN_VALID only
matters if SPARSEMEM is set. So risc-v probably doesn't need to set it
and we just need a #ifdef !CONFIG_FLATMEM around the pfn_valid
definition like other arches.

Logan

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