From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752237Ab1LSQ2n (ORCPT ); Mon, 19 Dec 2011 11:28:43 -0500 Received: from mail-yx0-f174.google.com ([209.85.213.174]:58078 "EHLO mail-yx0-f174.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751641Ab1LSQ2l (ORCPT ); Mon, 19 Dec 2011 11:28:41 -0500 Date: Mon, 19 Dec 2011 08:28:35 -0800 From: Tejun Heo To: Michal Simek Cc: Andrew Morton , Yinghai Lu , Benjamin Herrenschmidt , Sam Ravnborg , linux-mm@kvack.org, LKML Subject: Re: memblock and bootmem problems if start + size = 4GB Message-ID: <20111219162835.GA24519@google.com> References: <4EEF42F5.7040002@monstr.eu> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <4EEF42F5.7040002@monstr.eu> User-Agent: Mutt/1.5.20 (2009-06-14) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hello, Michal. On Mon, Dec 19, 2011 at 02:58:13PM +0100, Michal Simek wrote: > I have reached some problems with memblock and bootmem code for some configurations. > We can completely setup the whole system and all addresses in it. > The problem happens if we place main memory to the end of address space when > mem_start + size reach 4GB limit. > > For example: > mem_start 0xF000 0000 > mem_size 0x1000 0000 (or better lowmem size) > mem_end 0xFFFF FFFF > start + size 0x1 0000 0000 (u32 limit reached). > > I have done some patches which completely remove start + size values from architecture specific > code but I have found some problem in generic code too. > > For example in bootmem code where are three places where physaddr + size is used. > I would prefer to retype it to u64 because baseaddr and size don't need to be 2^n. > > Is it correct solution? If yes, I will create proper patch. Yeah, that's an inherent problem in using [) ranges but I think chopping off the last page probably is simpler and more robust solution. Currently, memblock_add_region() would simply ignore if address range overflows but making it just ignore the last page is several lines of addition. Wouldn't that be effective enough while staying very simple? Thanks. -- tejun