[ofa-general] Re: libmlx4 wc flash

[Roland Dreier]

 > > By the way, do you know what the best way to flush WC buffers for i386
 > > is?  I know on x86-64 sfence is the way to go, and on ia64 I think we
 > > want fc, but I'm not sure what the right thing is for for old 32-bit
 > > processors.
 > 
 > Maybe just disable WC there?

I think we want to use write combining on 32-bit kernels or 32-bit
userspace.  But I don't want to rely on SSE2 instructions for i386 binaries.

 > I don't think it works this way: if PAT is programmed to UC,
 > I think you get UC access with movntq. No?

You're right -- I misremembered what the non-temporal stuff does, but
I just checked and the manual says:

 "The memory type of the region being written to can override the
  non-temporal hint, if the memory address specified for the
  non-temporal store is in an uncacheable (UC) or write protected (WP)
  memory region."

 - R.