From mboxrd@z Thu Jan 1 00:00:00 1970 From: nico@fluxnic.net (Nicolas Pitre) Date: Mon, 10 Sep 2012 10:12:19 -0400 (EDT) Subject: [PATCH v3 02/31] arm64: Kernel booting and initialisation In-Reply-To: <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> <201209101353.34325.arnd@arndb.de> Message-ID: To: linux-arm-kernel@lists.infradead.org List-Id: linux-arm-kernel.lists.infradead.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