Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752040Ab0AKCVH (ORCPT ); Sun, 10 Jan 2010 21:21:07 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1751402Ab0AKCVG (ORCPT ); Sun, 10 Jan 2010 21:21:06 -0500 Received: from mga11.intel.com ([192.55.52.93]:22474 "EHLO mga11.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750940Ab0AKCVD convert rfc822-to-8bit (ORCPT ); Sun, 10 Jan 2010 21:21:03 -0500 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="4.49,251,1262592000"; d="scan'208";a="530105594" From: "Zheng, Shaohui" To: "Wu, Fengguang" CC: "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" , KAMEZAWA Hiroyuki Date: Mon, 11 Jan 2010 10:20:22 +0800 Subject: RE: [PATCH - resend] Memory-Hotplug: Fix the bug on interface /dev/mem for 64-bit kernel(v1) Thread-Topic: [PATCH - resend] Memory-Hotplug: Fix the bug on interface /dev/mem for 64-bit kernel(v1) Thread-Index: AcqQY0vnRq0EymTmSoSAxQPo6rCJSQB/riGg Message-ID: References: <20100108124851.GB6153@localhost> In-Reply-To: <20100108124851.GB6153@localhost> Accept-Language: en-US Content-Language: en-US X-MS-Has-Attach: X-MS-TNEF-Correlator: acceptlanguage: en-US Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 8BIT MIME-Version: 1.0 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 6054 Lines: 168 Thanks Fengguang, see and comments in the email. Only a few different understanding on variable max_low_pfn. Thanks & Regards, Shaohui -----Original Message----- From: Wu, Fengguang Sent: Friday, January 08, 2010 8:49 PM To: Zheng, Shaohui Cc: 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; KAMEZAWA Hiroyuki Subject: Re: [PATCH - resend] Memory-Hotplug: Fix the bug on interface /dev/mem for 64-bit kernel(v1) On Fri, Jan 08, 2010 at 11:32:07AM +0800, Zheng, Shaohui wrote: > Resend the patch to the mailing-list, the original patch URL is > http://patchwork.kernel.org/patch/69075/, it is not accepted without comments, > sent it again to review. > > Memory-Hotplug: Fix the bug on interface /dev/mem for 64-bit kernel > > The new added memory can not be access by interface /dev/mem, because we do not > update the variable high_memory. This patch add a new e820 entry in e820 table, > and update max_pfn, max_low_pfn and high_memory. > > We add a function update_pfn in file arch/x86/mm/init.c to udpate these > varibles. Memory hotplug does not make sense on 32-bit kernel, so we did not > concern it in this function. > > Signed-off-by: Shaohui Zheng > CC: Andi Kleen > CC: Wu Fengguang > CC: Li Haicheng > > --- > diff --git a/arch/x86/kernel/e820.c b/arch/x86/kernel/e820.c > index f50447d..b986246 100644 > --- a/arch/x86/kernel/e820.c > +++ b/arch/x86/kernel/e820.c > @@ -110,8 +110,8 @@ int __init e820_all_mapped(u64 start, u64 end, unsigned type) > /* > * Add a memory region to the kernel e820 map. > */ > -static void __init __e820_add_region(struct e820map *e820x, u64 start, u64 size, > - int type) > +static void __meminit __e820_add_region(struct e820map *e820x, u64 start, > + u64 size, int type) > { > int x = e820x->nr_map; > > @@ -126,7 +126,7 @@ static void __init __e820_add_region(struct e820map *e820x, u64 start, u64 size, > e820x->nr_map++; > } > > -void __init e820_add_region(u64 start, u64 size, int type) > +void __meminit e820_add_region(u64 start, u64 size, int type) > { > __e820_add_region(&e820, start, size, type); > } > diff --git a/arch/x86/mm/init.c b/arch/x86/mm/init.c > index d406c52..0474459 100644 > --- a/arch/x86/mm/init.c > +++ b/arch/x86/mm/init.c > @@ -1,6 +1,7 @@ > #include > #include > #include > +#include > > #include > #include > @@ -386,3 +387,30 @@ void free_initrd_mem(unsigned long start, unsigned long end) > free_init_pages("initrd memory", start, end); > } > #endif > + > +/** > + * After memory hotplug, the variable max_pfn, max_low_pfn and high_memory will > + * be affected, it will be updated in this function. Memory hotplug does not > + * make sense on 32-bit kernel, so we do did not concern it in this function. > + */ > +void __meminit __attribute__((weak)) update_pfn(u64 start, u64 size) > +{ > +#ifdef CONFIG_X86_64 > + unsigned long limit_low_pfn = 1UL<<(32 - PAGE_SHIFT); > + unsigned long start_pfn = start >> PAGE_SHIFT; > + unsigned long end_pfn = (start + size) >> PAGE_SHIFT; Strictly speaking, should use "end_pfn = PFN_UP(start + size);". [Zheng, Shaohui] I will use PFN_UP to replace it in new version. > + if (end_pfn > max_pfn) { > + max_pfn = end_pfn; > + high_memory = (void *)__va(max_pfn * PAGE_SIZE - 1) + 1; > + } > + > + /* 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();. 899 #ifdef CONFIG_X86_64 900 if (max_pfn > max_low_pfn) { 901 max_pfn_mapped = init_memory_mapping(1UL<<32, 902 max_pfn< + } > +#endif /* CONFIG_X86_64 */ > +} > diff --git a/include/linux/bootmem.h b/include/linux/bootmem.h > index b10ec49..6693414 100644 > --- a/include/linux/bootmem.h > +++ b/include/linux/bootmem.h > @@ -13,6 +13,7 @@ > > extern unsigned long max_low_pfn; > extern unsigned long min_low_pfn; > +extern void update_pfn(u64 start, u64 size); > > /* > * highest page > diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c > index 030ce8a..ee7b2d6 100644 > --- a/mm/memory_hotplug.c > +++ b/mm/memory_hotplug.c > @@ -523,6 +523,14 @@ int __ref add_memory(int nid, u64 start, u64 size) > BUG_ON(ret); > } > > + /* update e820 table */ This comment can be eliminated - you already have the very readable printk :) [Zheng, Shaohui] I will remove this comment > + printk(KERN_INFO "Adding memory region to e820 table (start:%016Lx, size:%016Lx).\n", > + (unsigned long long)start, (unsigned long long)size); > + e820_add_region(start, size, E820_RAM); > + /* update max_pfn, max_low_pfn and high_memory */ > + update_pfn(start, size); How about renaming function to update_end_of_memory_vars()? [Zheng, Shaohui] Agree. Thanks, Fengguang -- 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/