Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752979Ab3F2S1m (ORCPT ); Sat, 29 Jun 2013 14:27:42 -0400 Received: from terminus.zytor.com ([198.137.202.10]:60621 "EHLO mail.zytor.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751983Ab3F2S1j (ORCPT ); Sat, 29 Jun 2013 14:27:39 -0400 User-Agent: K-9 Mail for Android In-Reply-To: <20130629175743.GA382@mtj.dyndns.org> References: <1372467663-31425-1-git-send-email-santosh.shilimkar@ti.com> <20130629152959.GB31339@mtj.dyndns.org> <20130629172123.GA3353@n2100.arm.linux.org.uk> <20130629175743.GA382@mtj.dyndns.org> MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Subject: Re: [PATCH] WIP: HACK: LPAE, BOOTMEM and NO_BOOTMEM From: "H. Peter Anvin" Date: Sat, 29 Jun 2013 11:23:43 -0700 To: Tejun Heo , Russell King - ARM Linux CC: Santosh Shilimkar , linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, Catalin Marinas , Will Deacon , Nicolas Pitre , Ingo Molnar , Andrew Morton , Benjamin Herrenschmidt , Paul Mackerras , "David S. Miller" , sparclinux@vger.kernel.org, Sam Ravnborg , linux-arch@vger.kernel.org Message-ID: <23a25575-484a-4013-b555-f7f79534589d@email.android.com> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2442 Lines: 59 3 makes sense to me. Tejun Heo wrote: >( Expanding cc list, original thread is at > http://thread.gmane.org/gmane.linux.kernel/1518046 ) > >Hello, > >On Sat, Jun 29, 2013 at 06:21:24PM +0100, Russell King - ARM Linux >wrote: >> Unfortunately, that has not been true on ARM - it's very common for >> there to be an offset on physical memory, sometimes of the order of >> 3GB or more. This is because on reset, ARMs start executing the code >> at physical address zero, which therefore can't be RAM - and there's >> a desire to avoid complex switching games in hardware to temporarily >> map ROM there instead of RAM. >> >> On these SoCs which Santosh is working on, the main physical memory >> mapping is above 4GB, with just a small alias below 4GB to allow the >> system to boot without the MMU being on, as they may have more than >> 4GB of RAM. As I understand it, the small alias below 4GB is not >> suitable for use as a "lowmem" mapping. > >Ah, okay, so the @limit which is in physical address can be over 4GB >even for lowmem mappings and alloc_bootmem takes them in ulongs, >urghhh.... > >Given that still about half of the archs aren't using memblock yet, I >think there are three options. > >1. Converting all bootmem interface to use physaddr_t. But that's > what memblock is. > >2. Introducing new interface. Easier right now but the danger there > is that it might end up duplicating most of alloc_bootmem() > interface anyway and we'll have yet another variant of early mem > allocator to enjoy. > >3. Make all generic code use memblock interface instead of bootmem and > implement memblock wrapper on archs which don't use memblock yet. > We'll probably need to sort out different combinations of > HAVE_MEMBLOCK and NO_BOOTMEM. If this is doable, it probably is > the most future proof way. While it adds new memblock interface > built on top of bootmem, it would also allow removing the bootmem > interface built on top of memblock - ie. nobootmem.c, which > probably is what we should have done from the beginning. > >What do you guys think? > >Thanks. -- Sent from my mobile phone. Please excuse brevity and lack of formatting. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/