From mboxrd@z Thu Jan 1 00:00:00 1970 Return-path: Received: from mail-wr1-x432.google.com ([2a00:1450:4864:20::432]) by bombadil.infradead.org with esmtps (Exim 4.90_1 #2 (Red Hat Linux)) id 1gpjHQ-0000F0-JF for barebox@lists.infradead.org; Sat, 02 Feb 2019 00:35:34 +0000 Received: by mail-wr1-x432.google.com with SMTP id r17so2961439wrp.2 for ; Fri, 01 Feb 2019 16:35:29 -0800 (PST) MIME-Version: 1.0 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> In-Reply-To: <20190201074711.clrwidodo5hpqb7y@pengutronix.de> From: Andrey Smirnov Date: Fri, 1 Feb 2019 16:35:16 -0800 Message-ID: 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: Sascha Hauer Cc: Barebox List , Peter Mamonov 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: barebox@ZII i.MX8MQ Ultra Zest Board:/ md -b 0x7ffffffffffffffe 7ffffffffffffffe: ff . barebox@ZII i.MX8MQ Ultra Zest Board:/ md -b 0x7fffffffffffffff barebox@ZII i.MX8MQ Ultra Zest Board:/ md -b 0x8fffffffffffffff lseek: Invalid argument barebox@ZII i.MX8MQ Ultra Zest Board:/ md -b 0xfffffffffffffff0 lseek: Invalid argument Thanks, Andrey Smirnov _______________________________________________ barebox mailing list barebox@lists.infradead.org http://lists.infradead.org/mailman/listinfo/barebox