From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757372Ab2IJOM0 (ORCPT ); Mon, 10 Sep 2012 10:12:26 -0400 Received: from relais.videotron.ca ([24.201.245.36]:36975 "EHLO relais.videotron.ca" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753724Ab2IJOMW (ORCPT ); Mon, 10 Sep 2012 10:12:22 -0400 MIME-version: 1.0 Content-transfer-encoding: 7BIT Content-type: TEXT/PLAIN; CHARSET=US-ASCII Date: Mon, 10 Sep 2012 10:12:19 -0400 (EDT) From: Nicolas Pitre To: Arnd Bergmann Cc: Catalin Marinas , Jean-Christophe PLAGNIOL-VILLARD , "linux-arch@vger.kernel.org" , "linux-kernel@vger.kernel.org" , "linux-arm-kernel@lists.infradead.org" Subject: Re: [PATCH v3 02/31] arm64: Kernel booting and initialisation In-reply-to: <201209101353.34325.arnd@arndb.de> Message-id: References: <1347035226-18649-1-git-send-email-catalin.marinas@arm.com> <20120910055339.GC31430@game.jcrosoft.org> <20120910125137.GC27042@arm.com> <201209101353.34325.arnd@arndb.de> User-Agent: Alpine 2.02 (LFD 1266 2009-07-14) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, 10 Sep 2012, Arnd Bergmann wrote: > On Monday 10 September 2012, Catalin Marinas wrote: > > On Mon, Sep 10, 2012 at 06:53:39AM +0100, Jean-Christophe PLAGNIOL-VILLARD wrote: > > > On 19:29 Sun 09 Sep , Nicolas Pitre wrote: > > > > On Sun, 9 Sep 2012, Jean-Christophe PLAGNIOL-VILLARD wrote: > > > > > On 17:26 Fri 07 Sep , Catalin Marinas wrote: > > > > > > +The image must be placed at the specified offset (currently 0x80000) > > > > > > +from the start of the system RAM and called there. The start of the > > > > > > +system RAM must be aligned to 2MB. > > > > > can we drop this > > > > > > > > Drop what? > > > > And why? > > > This contrain the must be loadable at any address > > > > You can't easily load the kernel image at any address, unless it can > > relocate itself and you have a way to specify PHYS_OFFSET. We don't want > > a compile-time PHYS_OFFSET, the kernel detects it at boot time based on > > the load address. > > I think a bunch of other architectures can have relocatable kernels, which > is useful e.g. for kdump. It does imply a small runtime cost and may have > other disadvantages though. Relocatable in physical space is what kdump actually needs, and that's what we already have here (as well as on ARM32 for that matter with CONFIG_ARM_PATCH_PHYS_VIRT). Relocatable in the virtual space is costly and we shouldn't need to go there. Nicolas