Re: [PATCH for-4.8 03/12] powerpc/mm: use _raw variant of page table accessors

Hi David,

quoted

This switch few of the page table accessor to use the __raw variant
and does the cpu to big endian conversion of constants. This helps
in generating better code.  

It might be better to say that checks for a value being 0 don't depend
on the endianness.

In which case you want a function that return !!xxx_raw() itself.

OTOH it might be worth finding out why the cpu's byteswapping memory
accessors aren't used - which might save the byteswap instruction
sequence in all paths.

There was a discussion about this on the list. In short, we found a
couple of reasons. Accesses often use READ_ONCE() which might cause
problems. The bigger issue is if the pte is accessed via larx/stcx. We
have no byte reversed larx/stcx instructions.

Anton