From mboxrd@z Thu Jan 1 00:00:00 1970 Return-path: Received: from metis.ext.pengutronix.de ([2001:67c:670:201:290:27ff:fe1d:cc33]) by bombadil.infradead.org with esmtps (Exim 4.90_1 #2 (Red Hat Linux)) id 1gqYs7-0006vd-DF for barebox@lists.infradead.org; Mon, 04 Feb 2019 07:40:53 +0000 Date: Mon, 4 Feb 2019 08:40:45 +0100 From: Sascha Hauer Message-ID: <20190204074045.bhbwfjw6777idk7l@pengutronix.de> References: <20190129065549.29161-1-andrew.smirnov@gmail.com> <20190129065549.29161-19-andrew.smirnov@gmail.com> <20190129084847.spkfbeksb7xne46g@pengutronix.de> <20190131105452.smetw36klsxmvtaq@localhost.localdomain> <20190131125028.glbnt55zmhqowi6p@localhost.localdomain> <20190201074711.clrwidodo5hpqb7y@pengutronix.de> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "barebox" Errors-To: barebox-bounces+u.kleine-koenig=pengutronix.de@lists.infradead.org Subject: Re: [PATCH v2 18/19] drivers: mem: Create file to access second half of 64-bit memory To: Andrey Smirnov Cc: Barebox List , Peter Mamonov On Fri, Feb 01, 2019 at 04:35:16PM -0800, Andrey Smirnov wrote: > On Thu, Jan 31, 2019 at 11:47 PM Sascha Hauer wrote: > > > > On Thu, Jan 31, 2019 at 03:50:28PM +0300, Peter Mamonov wrote: > > > On Thu, Jan 31, 2019 at 01:54:52PM +0300, Peter Mamonov wrote: > > > > Hello, Andrey, > > > > > > > > > In order to allow access to second half of address space on 64-bit > > > > > machines, add code that creates /dev/highmem dedicated for that. > > > > > > > > > > Note that due to maximum file size being limited to MAX_LFS_FILESIZE > > > > > or 0x7fff_ffff_ffff_ffff bytes at addresses 0x7fff_ffff_ffff_ffff and > > > > > 0xffff_ffff_ffff_ffff cannot be access through /dev/mem and > > > > > /dev/hightmem correspondingly. > > > > > > > > Does it imply using `-s /dev/highmem` argument when accessing addresses beyond > > > > MAX_LFS_FILESIZE? That's not very convenient: > > > > > > > > $ git grep -l /dev/mem > > > > commands/crc.c > > > > commands/digest.c > > > > commands/disasm.c > > > > commands/md.c > > > > commands/memcmp.c > > > > commands/memcpy.c > > > > commands/memset.c > > > > commands/mm.c > > > > commands/mw.c > > > > > > I've forgotten to mention, that all meaningful MIPS64 virtual addresses > > > belong to the 2nd half of the address space. Except for user segment addresses > > > which are not used in barebox. > > > > In that case our only option seems to be to use an unsigned 64bit type > > for filesize. We would need an additional lseek like function which > > is able to reach the upper half of the address space and with regular > > lseek simply only the lower half would be reachable. > > > > Note that currently we don't seem to have a problem as even with Andreys > > series applied we can still 'md' the whole address space. The test if we > > lseek outside the file never triggers since the signed comparison of > > offset > f->size never evaluates to true for f->size == S64_MAX. > > > > I am a bit confused by this statement. I agree The check for pos > > f->size won't evaluate to true if f->size == S64_MAX, but the pos < 0, > will. On my i.MX8MQ board with all but "drivers: mem: Create file to > access second half of 64-bit memory" applied I have: Sorry, my bad. I accidently looked at a tree that didn't have the patches applied. You're right of course. Sascha -- Pengutronix e.K. | | Industrial Linux Solutions | http://www.pengutronix.de/ | Peiner Str. 6-8, 31137 Hildesheim, Germany | Phone: +49-5121-206917-0 | Amtsgericht Hildesheim, HRA 2686 | Fax: +49-5121-206917-5555 | _______________________________________________ barebox mailing list barebox@lists.infradead.org http://lists.infradead.org/mailman/listinfo/barebox