[RFC] powerpc/mm: honor O_SYNC flag for memory map

[Segher Boessenkool]

> So what you are saying is that if the kernel has mapped a physical
> page as cacheable while user application is trying to map it as
> non-cacheable, there will be machine checks and checkstops rather than
> just performance drop?  This is new to me.  Could you elaborate a bit?

If some data is in cache at a certain physical address, and you then
do an uncached read from that address, on at least some CPUs both the
bus interface and the cache will reply.  Bang, machine check.

Writes are problematic as well.


Segher