[PATCH] powerpc/mm: Add _PAGE_SAO to _PAGE_CACHE_CTL mask

[Michael Ellerman]

Reza Arbab <arbab at linux.ibm.com> writes:

> On Tue, Jan 29, 2019 at 08:37:28PM +0530, Aneesh Kumar K.V wrote:
>>Not sure what the fix is about. We set the related hash pte flags via
>>
>>	if ((pteflags & _PAGE_CACHE_CTL) == _PAGE_TOLERANT)
>>		rflags |= HPTE_R_I;
>>	else if ((pteflags & _PAGE_CACHE_CTL) == _PAGE_NON_IDEMPOTENT)
>>		rflags |= (HPTE_R_I | HPTE_R_G);
>>	else if ((pteflags & _PAGE_CACHE_CTL) == _PAGE_SAO)
>>		rflags |= (HPTE_R_W | HPTE_R_I | HPTE_R_M);
>
> Again, nothing broken here, just a code readability thing. As Alexey 
> (and Charlie) noted, given the above it is a little confusing to define 
> _PAGE_CACHE_CTL this way:
>
>   #define _PAGE_CACHE_CTL      (_PAGE_NON_IDEMPOTENT | _PAGE_TOLERANT)

Yeah that's confusing I agree.

It's not really a maintainability thing, because those bits are in the
architecture, so they can't change.

> I like Alexey's idea, maybe just use a literal?
>
>   #define _PAGE_CACHE_CTL 0x30

I prefer your original patch. It serves as documentation on what values
we expect to see in that field.

cheers