[PATCH] arm64: mmu: set the contiguous for kernel mappings when appropriate

[Ard Biesheuvel]

On 11 October 2016 at 09:48, Steve Capper <steve.capper at linaro.org> wrote:
>
>
> On 11 October 2016 at 08:44, Mark Rutland <mark.rutland at arm.com> wrote:
>>
>> Hi Ard,
>>
>> On Mon, Oct 10, 2016 at 07:12:44PM +0100, Ard Biesheuvel wrote:
>> > Now that we no longer allow live kernel PMDs to be split, it is safe to
>> > start using the contiguous bit for kernel mappings. So set the
>> > contiguous
>> > bit in the kernel page mappings for regions whose size and alignment are
>> > suitable for this.
>> >
>> > Signed-off-by: Ard Biesheuvel <ard.biesheuvel at linaro.org>
>>
>> Given the splitting is now gone, using the contiguous bit makes sense to
>> me.
>>
>> With 16K pages, we can have contiguous PMD entries. Should we handle
>> those,
>> too? e.g. have separate {PMD,PTE}_CONT{,_SIZE}?
>>
>> Otherwise, I have some comments below.
>
>
> Hi,
>
> So in arch/arm64/include/asm/pgtable-hwdef.h, we have:
> CONT_PTE_SHIFT
> CONT_PMD_SHIFT
> CONT_PTES
> CONT_PMDS
> CONT_PTE_SIZE
> CONT_PTE_MASK
> ...
>
> which are used by the contiguous hint HugeTLB code.
> Can those be adopted instead of CONT_MASK and CONT_SIZE?
>

That seems more appropriate, yes. I wonder why we have CONT_MASK and
CONT_SIZE in the first place then.