From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753522Ab2GQGxz (ORCPT ); Tue, 17 Jul 2012 02:53:55 -0400 Received: from 173-166-109-252-newengland.hfc.comcastbusiness.net ([173.166.109.252]:49599 "EHLO bombadil.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752393Ab2GQGxv (ORCPT ); Tue, 17 Jul 2012 02:53:51 -0400 Date: Tue, 17 Jul 2012 02:53:38 -0400 From: Christoph Hellwig To: Arnd Bergmann Cc: Catalin Marinas , Pavel Machek , Ingo Molnar , Olof Johansson , "linux-kernel@vger.kernel.org" , Linus Torvalds , Russell King , Andrew Morton , Alan Cox Subject: Re: [PATCH 00/36] AArch64 Linux kernel port Message-ID: <20120717065338.GA24699@infradead.org> References: <1341608777-12982-1-git-send-email-catalin.marinas@arm.com> <20120714093032.GA23316@elf.ucw.cz> <20120715121644.GB10597@arm.com> <201207151943.08183.arnd@arndb.de> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <201207151943.08183.arnd@arndb.de> User-Agent: Mutt/1.5.21 (2010-09-15) X-SRS-Rewrite: SMTP reverse-path rewritten from by bombadil.infradead.org See http://www.infradead.org/rpr.html Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Sun, Jul 15, 2012 at 07:43:07PM +0000, Arnd Bergmann wrote: > Yes, I agree that's the best way to handle this. Compared to other > architectures, I think x86 is the only that allows booting either a > 32 or 64 bit kernel on the same system. We used to support 32 bit > kernels on 64 bit PowerMac, but nobody used it and we discontinued > it long ago. Tile 64 bit is actually incompatible with 32 bit kernels > at the architecture level and would require a third mode. On sparc, > parisc and mips, AFAIK we could support 32 bit kernels on 64 bit > machines, but never did. On mips it works just fine. On Sparc I don't think Linux ever did it, but Solaris did for a long time, as did (IIRC) NetBSD/OpenBSD.