Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1759153AbXELWKY (ORCPT ); Sat, 12 May 2007 18:10:24 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1751892AbXELWKM (ORCPT ); Sat, 12 May 2007 18:10:12 -0400 Received: from terminus.zytor.com ([192.83.249.54]:50498 "EHLO terminus.zytor.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751998AbXELWKL (ORCPT ); Sat, 12 May 2007 18:10:11 -0400 Message-ID: <46463AED.5060800@zytor.com> Date: Sat, 12 May 2007 15:08:45 -0700 From: "H. Peter Anvin" User-Agent: Thunderbird 2.0.0.0 (X11/20070419) MIME-Version: 1.0 To: "Eric W. Biederman" CC: Alexander van Heukelum , "Antonino A. Daplas" , Andi Kleen , Andrew Morton , Matt Domsch , Vivek Goyal , James Bottomley , Linux Kernel Mailing List Subject: Re: x86 setup rewrite tree ready for flamage^W review References: <464158E9.2000207@zytor.com> <1178806235.18785.1189115515@webmail.messagingengine.com> <46435F8A.1040203@zytor.com> <20070510220406.GA21110@mailshack.com> <4643A128.30302@zytor.com> <20070512122137.GA25944@mailshack.com> <464602DC.4050603@zytor.com> <46460E9E.9020308@zytor.com> In-Reply-To: X-Enigmail-Version: 0.95.0 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1180 Lines: 28 Eric W. Biederman wrote: > Ok. If you have tested on a wide variety of machines then I won't > worry about it. > > I guess if a cr0 write has always been synchronizing things should be > a safe practice. The practical danger is if you write to cr0 and the > pipeline is not flushed and the segment loads might execute as 16bit > mode segment register loads. I think this is more of a 486 or 586/Pentium > danger actually then a 386 one. Writes to CR0 are synchronizing and are documented as such. This is a fairly trivial consequence of it invoking microcode on every x86 ever created. > Hmm. I'm not certain about enabling protected mode but enabling paging > at least does appear to be documented to require a jump, before the P6 > core. Which may be why it is recommended for initializing protected > mode. Enabling paging is possibly a different matter. I can't speak on that particular subject with any authority. -hpa - 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/