From mboxrd@z Thu Jan 1 00:00:00 1970 From: Arnd Bergmann Subject: Re: [PATCH v3 02/31] arm64: Kernel booting and initialisation Date: Mon, 10 Sep 2012 13:53:34 +0000 Message-ID: <201209101353.34325.arnd@arndb.de> References: <1347035226-18649-1-git-send-email-catalin.marinas@arm.com> <20120910055339.GC31430@game.jcrosoft.org> <20120910125137.GC27042@arm.com> Mime-Version: 1.0 Content-Type: Text/Plain; charset="iso-8859-1" Content-Transfer-Encoding: 7bit Return-path: Received: from moutng.kundenserver.de ([212.227.126.186]:54016 "EHLO moutng.kundenserver.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756884Ab2IJNxl (ORCPT ); Mon, 10 Sep 2012 09:53:41 -0400 In-Reply-To: <20120910125137.GC27042@arm.com> Sender: linux-arch-owner@vger.kernel.org List-ID: To: Catalin Marinas Cc: Jean-Christophe PLAGNIOL-VILLARD , Nicolas Pitre , "linux-arch@vger.kernel.org" , "linux-kernel@vger.kernel.org" , "linux-arm-kernel@lists.infradead.org" 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. Arnd From mboxrd@z Thu Jan 1 00:00:00 1970 From: arnd@arndb.de (Arnd Bergmann) Date: Mon, 10 Sep 2012 13:53:34 +0000 Subject: [PATCH v3 02/31] arm64: Kernel booting and initialisation In-Reply-To: <20120910125137.GC27042@arm.com> References: <1347035226-18649-1-git-send-email-catalin.marinas@arm.com> <20120910055339.GC31430@game.jcrosoft.org> <20120910125137.GC27042@arm.com> Message-ID: <201209101353.34325.arnd@arndb.de> To: linux-arm-kernel@lists.infradead.org List-Id: linux-arm-kernel.lists.infradead.org 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. Arnd