From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752930Ab3F2T36 (ORCPT ); Sat, 29 Jun 2013 15:29:58 -0400 Received: from mail-ie0-f172.google.com ([209.85.223.172]:52724 "EHLO mail-ie0-f172.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752438Ab3F2T3z (ORCPT ); Sat, 29 Jun 2013 15:29:55 -0400 MIME-Version: 1.0 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> Date: Sat, 29 Jun 2013 12:29:55 -0700 X-Google-Sender-Auth: NrN7c7fIePfbetW8n3u5BYPBsNY Message-ID: Subject: Re: [PATCH] WIP: HACK: LPAE, BOOTMEM and NO_BOOTMEM From: Yinghai Lu To: Tejun Heo Cc: Russell King - ARM Linux , Santosh Shilimkar , linux-arm-kernel@lists.infradead.org, Linux Kernel Mailing List , Catalin Marinas , Will Deacon , Nicolas Pitre , Ingo Molnar , Andrew Morton , "H. Peter Anvin" , Benjamin Herrenschmidt , Paul Mackerras , "David S. Miller" , "sparclinux@vger.kernel.org" , Sam Ravnborg , linux-arch@vger.kernel.org Content-Type: text/plain; charset=ISO-8859-1 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Sat, Jun 29, 2013 at 10:57 AM, 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. is that 32bit ARM or 64bit ARM? > > 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? 2. looks more simple. but will use alloc_memblock as interface. We don't need to use __alloc_memory_core_early() directly, right? Thanks Yinghai From mboxrd@z Thu Jan 1 00:00:00 1970 From: Yinghai Lu Date: Sat, 29 Jun 2013 19:29:55 +0000 Subject: Re: [PATCH] WIP: HACK: LPAE, BOOTMEM and NO_BOOTMEM Message-Id: List-Id: 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> In-Reply-To: <20130629175743.GA382@mtj.dyndns.org> MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: Tejun Heo Cc: Russell King - ARM Linux , Santosh Shilimkar , linux-arm-kernel@lists.infradead.org, Linux Kernel Mailing List , Catalin Marinas , Will Deacon , Nicolas Pitre , Ingo Molnar , Andrew Morton , "H. Peter Anvin" , Benjamin Herrenschmidt , Paul Mackerras , "David S. Miller" , "sparclinux@vger.kernel.org" , Sam Ravnborg , linux-arch@vger.kernel.org On Sat, Jun 29, 2013 at 10:57 AM, 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. is that 32bit ARM or 64bit ARM? > > 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? 2. looks more simple. but will use alloc_memblock as interface. We don't need to use __alloc_memory_core_early() directly, right? Thanks Yinghai From mboxrd@z Thu Jan 1 00:00:00 1970 From: yinghai@kernel.org (Yinghai Lu) Date: Sat, 29 Jun 2013 12:29:55 -0700 Subject: [PATCH] WIP: HACK: LPAE, BOOTMEM and NO_BOOTMEM 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> Message-ID: To: linux-arm-kernel@lists.infradead.org List-Id: linux-arm-kernel.lists.infradead.org On Sat, Jun 29, 2013 at 10:57 AM, 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. is that 32bit ARM or 64bit ARM? > > 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? 2. looks more simple. but will use alloc_memblock as interface. We don't need to use __alloc_memory_core_early() directly, right? Thanks Yinghai