Messages in this thread | | | Date | Tue, 20 May 2008 15:21:13 -0700 (PDT) | From | Trent Piepho <> | Subject | Re: [PATCH] [POWERPC] Improve (in|out)_beXX() asm code |
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On Tue, 20 May 2008, Benjamin Herrenschmidt wrote: > On Tue, 2008-05-20 at 16:38 -0500, Scott Wood wrote: >> It looks like we rely on -fno-strict-aliasing to prevent reordering >> ordinary memory accesses (such as to DMA descriptors) past the I/O >> access. It won't prevent reordering of memory reads around an I/O >> read, >> though, which could be a problem if the I/O read result determines >> the >> validity of the DMA buffer. IMHO, a memory clobber would be better. > > We probably want a full "memory" clobber then...
As far as I could tell, no other arch has a full memory clobber. I can see the argument for changing the Linux model to be stricter and less efficient, but easier to program for. Not that I entirely agree with it.
But I don't see a good reason for why powerpc should be different than everything else.
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