Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751895Ab0ALCfA (ORCPT ); Mon, 11 Jan 2010 21:35:00 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1750890Ab0ALCe7 (ORCPT ); Mon, 11 Jan 2010 21:34:59 -0500 Received: from mga11.intel.com ([192.55.52.93]:18590 "EHLO mga11.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750783Ab0ALCe7 (ORCPT ); Mon, 11 Jan 2010 21:34:59 -0500 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="4.49,259,1262592000"; d="scan'208";a="763378561" Date: Tue, 12 Jan 2010 10:33:08 +0800 From: Wu Fengguang To: KAMEZAWA Hiroyuki Cc: "Zheng, Shaohui" , "linux-mm@kvack.org" , "akpm@linux-foundation.org" , "linux-kernel@vger.kernel.org" , "ak@linux.intel.com" , "y-goto@jp.fujitsu.com" , Dave Hansen , "x86@kernel.org" Subject: Re: [PATCH - resend] Memory-Hotplug: Fix the bug on interface /dev/mem for 64-bit kernel(v1) Message-ID: <20100112023307.GA16661@localhost> References: <20100108124851.GB6153@localhost> <20100111124303.GA21408@localhost> <20100112093031.0fc6877f.kamezawa.hiroyu@jp.fujitsu.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20100112093031.0fc6877f.kamezawa.hiroyu@jp.fujitsu.com> User-Agent: Mutt/1.5.18 (2008-05-17) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 5183 Lines: 169 On Tue, Jan 12, 2010 at 08:30:31AM +0800, KAMEZAWA Hiroyuki wrote: > On Mon, 11 Jan 2010 20:43:03 +0800 > Wu Fengguang wrote: > > > > > + /* if add to low memory, update max_low_pfn */ > > > > + if (unlikely(start_pfn < limit_low_pfn)) { > > > > + if (end_pfn <= limit_low_pfn) > > > > + max_low_pfn = end_pfn; > > > > + else > > > > + max_low_pfn = limit_low_pfn; > > > > > > X86_64 actually always set max_low_pfn=max_pfn, in setup_arch(): > > > [Zheng, Shaohui] there should be some misunderstanding, I read the > > > code carefully, if the total memory is under 4G, it always > > > max_low_pfn=max_pfn. If the total memory is larger than 4G, > > > max_low_pfn means the end of low ram. It set > > > > > max_low_pfn = e820_end_of_low_ram_pfn();. > > > > The above line is very misleading.. In setup_arch(), it will be > > overrode by the following block. > > > > Hmmm....could you rewrite /dev/mem to use kernel/resource.c other than > modifing e820 maps. ? > Two reasons. > - e820map is considerted to be stable, read-only after boot. > - We don't need to add more x86 special codes. Sure, here it is :) --- x86: use the generic page_is_ram() The generic resource based page_is_ram() works better with memory hotplug/hotremove. So switch the x86 e820map based code to it. CC: Andi Kleen CC: KAMEZAWA Hiroyuki Signed-off-by: Wu Fengguang --- arch/x86/include/asm/page_types.h | 1 arch/x86/mm/ioremap.c | 37 ---------------------------- kernel/resource.c | 17 ++++++++++++ 3 files changed, 17 insertions(+), 38 deletions(-) --- linux-mm.orig/arch/x86/include/asm/page_types.h 2010-01-12 10:31:01.000000000 +0800 +++ linux-mm/arch/x86/include/asm/page_types.h 2010-01-12 10:31:44.000000000 +0800 @@ -34,19 +34,18 @@ #ifdef CONFIG_X86_64 #include #else #include #endif /* CONFIG_X86_64 */ #ifndef __ASSEMBLY__ -extern int page_is_ram(unsigned long pagenr); extern int devmem_is_allowed(unsigned long pagenr); extern unsigned long max_low_pfn_mapped; extern unsigned long max_pfn_mapped; extern unsigned long init_memory_mapping(unsigned long start, unsigned long end); extern void initmem_init(unsigned long start_pfn, unsigned long end_pfn, --- linux-mm.orig/arch/x86/mm/ioremap.c 2010-01-12 10:31:01.000000000 +0800 +++ linux-mm/arch/x86/mm/ioremap.c 2010-01-12 10:31:44.000000000 +0800 @@ -18,55 +18,18 @@ #include #include #include #include #include #include #include "physaddr.h" -int page_is_ram(unsigned long pagenr) -{ - resource_size_t addr, end; - int i; - - /* - * A special case is the first 4Kb of memory; - * This is a BIOS owned area, not kernel ram, but generally - * not listed as such in the E820 table. - */ - if (pagenr == 0) - return 0; - - /* - * Second special case: Some BIOSen report the PC BIOS - * area (640->1Mb) as ram even though it is not. - */ - if (pagenr >= (BIOS_BEGIN >> PAGE_SHIFT) && - pagenr < (BIOS_END >> PAGE_SHIFT)) - return 0; - - for (i = 0; i < e820.nr_map; i++) { - /* - * Not usable memory: - */ - if (e820.map[i].type != E820_RAM) - continue; - addr = (e820.map[i].addr + PAGE_SIZE-1) >> PAGE_SHIFT; - end = (e820.map[i].addr + e820.map[i].size) >> PAGE_SHIFT; - - - if ((pagenr >= addr) && (pagenr < end)) - return 1; - } - return 0; -} - /* * Fix up the linear direct mapping of the kernel to avoid cache attribute * conflicts. */ int ioremap_change_attr(unsigned long vaddr, unsigned long size, unsigned long prot_val) { unsigned long nrpages = size >> PAGE_SHIFT; int err; --- linux-mm.orig/kernel/resource.c 2010-01-12 10:31:01.000000000 +0800 +++ linux-mm/kernel/resource.c 2010-01-12 10:31:44.000000000 +0800 @@ -298,18 +298,35 @@ int walk_system_ram_range(unsigned long #endif static int __is_ram(unsigned long pfn, unsigned long nr_pages, void *arg) { return 24; } int __attribute__((weak)) page_is_ram(unsigned long pfn) { +#ifdef CONFIG_X86 + /* + * A special case is the first 4Kb of memory; + * This is a BIOS owned area, not kernel ram, but generally + * not listed as such in the E820 table. + */ + if (pfn == 0) + return 0; + + /* + * Second special case: Some BIOSen report the PC BIOS + * area (640->1Mb) as ram even though it is not. + */ + if (pfn >= (BIOS_BEGIN >> PAGE_SHIFT) && + pfn < (BIOS_END >> PAGE_SHIFT)) + return 0; +#endif return 24 == walk_system_ram_range(pfn, 1, NULL, __is_ram); } /* * Find empty slot in the resource tree given range and alignment. */ static int find_resource(struct resource *root, struct resource *new, resource_size_t size, resource_size_t min, resource_size_t max, resource_size_t align, -- 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/