Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754771Ab3IZW6O (ORCPT ); Thu, 26 Sep 2013 18:58:14 -0400 Received: from terminus.zytor.com ([198.137.202.10]:57458 "EHLO mail.zytor.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754436Ab3IZW6M (ORCPT ); Thu, 26 Sep 2013 18:58:12 -0400 User-Agent: K-9 Mail for Android In-Reply-To: <20130926155205.7f364b64c4a0fae77d4ca15d@linux-foundation.org> References: <5241D897.1090905@gmail.com> <5241DA5B.8000909@gmail.com> <20130926155205.7f364b64c4a0fae77d4ca15d@linux-foundation.org> MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Subject: Re: [PATCH v5 4/6] x86/mem-hotplug: Support initialize page tables in bottom-up From: "H. Peter Anvin" Date: Thu, 26 Sep 2013 15:57:06 -0700 To: Andrew Morton , Zhang Yanfei CC: "Rafael J . Wysocki" , lenb@kernel.org, Thomas Gleixner , mingo@elte.hu, Tejun Heo , Toshi Kani , Wanpeng Li , Thomas Renninger , Yinghai Lu , Jiang Liu , Wen Congyang , Lai Jiangshan , isimatu.yasuaki@jp.fujitsu.com, izumi.taku@jp.fujitsu.com, Mel Gorman , Minchan Kim , mina86@mina86.com, gong.chen@linux.intel.com, vasilis.liaskovitis@profitbricks.com, lwoodman@redhat.com, Rik van Riel , jweiner@redhat.com, prarit@redhat.com, "x86@kernel.org" , linux-doc@vger.kernel.org, "linux-kernel@vger.kernel.org" , Linux MM , linux-acpi@vger.kernel.org, imtangchen@gmail.com, Zhang Yanfei Message-ID: <59d57cc9-9f4b-4f28-95d0-a526bd0b9a29@email.android.com> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2176 Lines: 63 Can we put this in a common header somewhere? Andrew Morton wrote: >On Wed, 25 Sep 2013 02:30:51 +0800 Zhang Yanfei > wrote: > >> From: Tang Chen >> >> The Linux kernel cannot migrate pages used by the kernel. As a >> result, kernel pages cannot be hot-removed. So we cannot allocate >> hotpluggable memory for the kernel. >> >> In a memory hotplug system, any numa node the kernel resides in >> should be unhotpluggable. And for a modern server, each node could >> have at least 16GB memory. So memory around the kernel image is >> highly likely unhotpluggable. >> >> ACPI SRAT (System Resource Affinity Table) contains the memory >> hotplug info. But before SRAT is parsed, memblock has already >> started to allocate memory for the kernel. So we need to prevent >> memblock from doing this. >> >> So direct memory mapping page tables setup is the case. >init_mem_mapping() >> is called before SRAT is parsed. To prevent page tables being >allocated >> within hotpluggable memory, we will use bottom-up direction to >allocate >> page tables from the end of kernel image to the higher memory. >> >> ... >> >> + kernel_end = __pa_symbol(_end); > >__pa_symbol() is implemented only on mips and x86. > >I stole the mips implementation like this: > >--- a/mm/memblock.c~a >+++ a/mm/memblock.c >@@ -187,8 +187,11 @@ phys_addr_t __init_memblock memblock_fin > /* avoid allocating the first page */ > start = max_t(phys_addr_t, start, PAGE_SIZE); > end = max(start, end); >+#ifdef CONFIG_X86 > kernel_end = __pa_symbol(_end); >- >+#else >+ kernel_end = __pa(RELOC_HIDE((unsigned long)(_end), 0)); >+#endif > /* > * try bottom-up allocation only when bottom-up mode > * is set and @end is above the kernel image. > >just so I can get a -mm release out the door. -- Sent from my mobile phone. Please pardon 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/