From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:44891) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1g9tz9-0000i7-TU for qemu-devel@nongnu.org; Tue, 09 Oct 2018 11:31:48 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1g9tz6-0000aX-Kf for qemu-devel@nongnu.org; Tue, 09 Oct 2018 11:31:47 -0400 Received: from mx1.redhat.com ([209.132.183.28]:39146) by eggs.gnu.org with esmtps (TLS1.0:DHE_RSA_AES_256_CBC_SHA1:32) (Exim 4.71) (envelope-from ) id 1g9tz4-0000Vo-OQ for qemu-devel@nongnu.org; Tue, 09 Oct 2018 11:31:43 -0400 Date: Tue, 9 Oct 2018 16:31:32 +0100 From: Daniel =?utf-8?B?UC4gQmVycmFuZ8Op?= Message-ID: <20181009153132.GL22838@redhat.com> Reply-To: Daniel =?utf-8?B?UC4gQmVycmFuZ8Op?= References: <20181009125541.24455-1-berrange@redhat.com> <20181009125541.24455-5-berrange@redhat.com> <20181009150629.GK22838@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: Subject: Re: [Qemu-devel] [PATCH 4/6] crypto: convert xts_tweak_encdec to use xts_uint128 type List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Alberto Garcia Cc: qemu-devel@nongnu.org On Tue, Oct 09, 2018 at 05:30:25PM +0200, Alberto Garcia wrote: > >> > for (i = 0; i < lim; i++) { > >> > - xts_tweak_encdec(datactx, decfunc, src, dst, (uint8_t *)&T); > >> > + xts_uint128 S, D; > >> > + > >> > + memcpy(&S, src, XTS_BLOCK_SIZE); > >> > + xts_tweak_encdec(datactx, decfunc, &S, &D, &T); > >> > + memcpy(dst, &D, XTS_BLOCK_SIZE); > >> > >> Why do you need S and D? > > > > I think src & dst pointers can't be guaranteed to be aligned > > sufficiently for int64 operations, if we just cast from uint8t*. > > I see. I did a quick test without the memcpy() calls and it doesn't seem > to have a visible effect on performance, but if it turns out that it > does then maybe this is worth investigating further. I suspect all > buffers received by this code are allocated with qemu_try_blockalign() > anyway, so it should be safe. The extra memcpy() calls certainly had a perf impact when I added them, so if we can determine that we can safely do without, that would be desirable. Regards, Daniel -- |: https://berrange.com -o- https://www.flickr.com/photos/dberrange :| |: https://libvirt.org -o- https://fstop138.berrange.com :| |: https://entangle-photo.org -o- https://www.instagram.com/dberrange :|