Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751155AbVKKUWT (ORCPT ); Fri, 11 Nov 2005 15:22:19 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1751161AbVKKUWT (ORCPT ); Fri, 11 Nov 2005 15:22:19 -0500 Received: from smtp.osdl.org ([65.172.181.4]:63899 "EHLO smtp.osdl.org") by vger.kernel.org with ESMTP id S1751155AbVKKUWS (ORCPT ); Fri, 11 Nov 2005 15:22:18 -0500 Date: Fri, 11 Nov 2005 12:22:07 -0800 (PST) From: Linus Torvalds To: Zachary Amsden cc: Pavel Machek , Andrew Morton , Linux Kernel Mailing List , "H. Peter Anvin" , Zwane Mwaikambo , Pratap Subrahmanyam , Christopher Li , "Eric W. Biederman" , Ingo Molnar Subject: Re: [PATCH 1/10] Cr4 is valid on some 486s In-Reply-To: <4374FB89.6000304@vmware.com> Message-ID: References: <200511100032.jAA0WgUq027712@zach-dev.vmware.com> <20051111103605.GC27805@elf.ucw.cz> <4374F2D5.7010106@vmware.com> <4374FB89.6000304@vmware.com> MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1137 Lines: 35 On Fri, 11 Nov 2005, Zachary Amsden wrote: > > Yes, this is fine, but is it worth writing the feature discovery code? I > suppose it doesn't matter, as it gets jettisoned after init. I guess it is > just preference. Well, you could do the feature discovery by trying to take a fault early at boot-time. That's how we verify that write-protect works, and how we check that math exceptions come in the right way.. > Could we consider doing the same with LOCK prefix for SMP kernels booted on > UP? Evil grin. Not so evil - I think it's been discussed. Not with alternates (not worth it), but it wouldn't be hard to do: just add a new section for "lock address", and have each inline asm that does a lock prefix do basically 1: lock ; xyzzy .section .lock.address .long 1b .previous and then just walk the ".lock.address" thing and turn all locks into 0x90 (nop). Linus - 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/