On 31 March 2014 20:36, Russell King - ARM Linux <linux@xxxxxxxxxxxxxxxx> wrote: > On Mon, Mar 31, 2014 at 08:22:43PM +0200, Ard Biesheuvel wrote: >> On 31 March 2014 19:24, Catalin Marinas <catalin.marinas@xxxxxxx> wrote: >> > It actually affects arch/arm as well which selects >> > HAVE_EFFICIENT_UNALIGNED_ACCESS for v6/v7 and uses the generic >> > unaligned.h >> > >> >> Oops, my bad. I did a quick 'find -name unaligned.h' but misread 'arc' >> for 'arm'. >> >> @Russell: ARM is a user of asm-generic/unaligned.h, and I proposed a >> patch to asm-generic that switches to unaligned accesses if >> HAVE_EFFICIENT_UNALIGNED_ACCESS is set by the arch. This should affect >> a fair amount of code living under net/ and drivers/ that don't test >> for the Kconfig symbol but expect get_unaligned_xx/put_unaligned_xx to >> turn into something suitable depending on the arch. Any objections? > > I'm not sure what you're talking about here, or what change you're > proposing. Without any kind of frame of reference, I can't comment. > Sorry. > My apologies. I assumed the mail thread including a link to the patch would be clear enough. Currently, asm-generic's version of unaligned.h (defining stuff like get_unaligned() and put_unaligned()) unconditionally defaults to the most cautious method of performing unaligned memory accesses, even if the Kconfig symbol HAVE_EFFICIENT_UNALIGNED_ACCESS is defined. However, in that case, it makes sense to use a definition for get_unaligned()/put_unaligned() that lets the hardware perform the unaligned accesses instead. So that is what I proposed here http://marc.info/?l=linux-arch&m=139594237116121&w=2 and in the mail exchange that followed, I stated that arm64 should be the only arch affected by this change. However, I didn't look carefully enough and, as Catalin pointed out, ARM will also be affected by it. So that is why I redirected this thread to you: would you object to changing asm-generic/unaligned.h so that calls to get_aligned()/put_aligned() on ARM v6/v7 will let the CPU perform the unaligned access? Regards, Ard. -- To unsubscribe from this list: send the line "unsubscribe linux-arch" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
