From mboxrd@z Thu Jan 1 00:00:00 1970 Subject: Re: kernel oops due to unaligned access with lswi From: Benjamin Herrenschmidt Reply-To: benh@kernel.crashing.org To: David Edelsohn Cc: Olaf Hering , Alan Modra , linuxppc-dev list In-Reply-To: <200311152259.hAFMxGT27464@makai.watson.ibm.com> References: <20031115210449.GA10105@suse.de> <20031115222430.GA13820@suse.de> <200311152230.hAFMUwT32990@makai.watson.ibm.com> <20031115224342.GA16897@suse.de> <200311152259.hAFMxGT27464@makai.watson.ibm.com> Content-Type: text/plain Message-Id: <1068977831.681.8.camel@gaston> Mime-Version: 1.0 Date: Sun, 16 Nov 2003 21:17:11 +1100 Sender: owner-linuxppc-dev@lists.linuxppc.org List-Id: On Sun, 2003-11-16 at 09:59, David Edelsohn wrote: > I didn't mean that lswi cannot take an alignment exception on some > PPC implementations, but that lswi is suppose to be able to handle block > loads from addresses with arbitrary alignment I remember beeing regulary told (I think by Apple while I was still doing MacOS hacking) that those string instructions were evil, deprecated, and should be avoided as they weren't peforming better than the equivalent set of load/store instructions... Is this still true ? In which case we may want to avoid generating them from gcc.. Also, if the 601 effectively gets alignement exceptions on these, it's quite bad to have them implicitely generated by gcc for memcpy's since our OFs seem to not implement the alignement handler for them, thus breaking our boot wrappers. Finally, the pem32b at least seem to be clear about not encouraging to use these especially on non-aligned accesses. It looks like a weird optimisation to do for memcpy... Ben. ** Sent via the linuxppc-dev mail list. See http://lists.linuxppc.org/