On Mon, Mar 31, 2014 at 08:51:54PM +0200, Ard Biesheuvel wrote: > 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? The change looks fine to me, but given where we are in the cycle, I'd rather hold off until after the merge window before queuing this up. -- FTTC broadband for 0.8mile line: now at 9.7Mbps down 460kbps up... slowly improving, and getting towards what was expected from it. -- 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
