Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755564AbaAWTcP (ORCPT ); Thu, 23 Jan 2014 14:32:15 -0500 Received: from gw-1.arm.linux.org.uk ([78.32.30.217]:46750 "EHLO pandora.arm.linux.org.uk" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1755504AbaAWTcK (ORCPT ); Thu, 23 Jan 2014 14:32:10 -0500 Date: Thu, 23 Jan 2014 19:31:37 +0000 From: Russell King - ARM Linux To: Nicolas Pitre Cc: Wang Nan , kexec@lists.infradead.org, Eric Biederman , Andrew Morton , Geng Hui , linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, stable@vger.kernel.org Subject: Re: [PATCH 3/3] ARM: allow kernel to be loaded in middle of phymem Message-ID: <20140123193137.GA15937@n2100.arm.linux.org.uk> References: <1390389916-8711-1-git-send-email-wangnan0@huawei.com> <1390389916-8711-4-git-send-email-wangnan0@huawei.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.5.19 (2009-01-05) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Jan 23, 2014 at 02:15:07PM -0500, Nicolas Pitre wrote: > On Wed, 22 Jan 2014, Wang Nan wrote: > > > This patch allows the kernel to be loaded at the middle of kernel awared > > physical memory. Before this patch, users must use mem= or device tree to cheat > > kernel about the start address of physical memory. > > > > This feature is useful in some special cases, for example, building a crash > > dump kernel. Without it, kernel command line, atag and devicetree must be > > adjusted carefully, sometimes is impossible. > > With CONFIG_PATCH_PHYS_VIRT the value for PHYS_OFFSET is determined > dynamically by rounding down the kernel image start address to the > previous 16MB boundary. In the case of a crash kernel, this might be > cleaner to simply readjust __pv_phys_offset during early boot and call > fixup_pv_table(), and then reserve away the memory from the previous > kernel. That will let you access that memory directly (with gdb for > example) and no pointer address translation will be required. We already have support in the kernel to ignore memory below the calculated PHYS_OFFSET. See 571b14375019c3a66ef70d4d4a7083f4238aca30. -- FTTC broadband for 0.8mile line: 5.8Mbps down 500kbps up. Estimation in database were 13.1 to 19Mbit for a good line, about 7.5+ for a bad. Estimate before purchase was "up to 13.2Mbit". -- 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/