Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756878AbYHGV5V (ORCPT ); Thu, 7 Aug 2008 17:57:21 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1751885AbYHGV5N (ORCPT ); Thu, 7 Aug 2008 17:57:13 -0400 Received: from smtp-outbound-1.vmware.com ([65.113.40.141]:37269 "EHLO smtp-outbound-1.vmware.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751344AbYHGV5N (ORCPT ); Thu, 7 Aug 2008 17:57:13 -0400 Subject: Re: [PATCH]Fix broken VMI in 2.6.27-rc.. From: Zachary Amsden To: "H. Peter Anvin" Cc: Alok Kataria , "torvalds@linux-foundation.org" , Ingo Molnar , the arch/x86 maintainers , LKML In-Reply-To: <489B6E83.7000202@kernel.org> References: <1218136365.23770.52.camel@alok-dev1> <489B6710.9000604@kernel.org> <1218144438.20178.336.camel@bodhitayantram.eng.vmware.com> <489B6A5C.8030400@kernel.org> <1218145344.20178.347.camel@bodhitayantram.eng.vmware.com> <489B6E83.7000202@kernel.org> Content-Type: text/plain Date: Thu, 07 Aug 2008 14:55:54 -0700 Message-Id: <1218146154.20178.352.camel@bodhitayantram.eng.vmware.com> Mime-Version: 1.0 X-Mailer: Evolution 2.22.2 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1424 Lines: 33 On Thu, 2008-08-07 at 14:52 -0700, H. Peter Anvin wrote: > Zachary Amsden wrote: > >>> > >> Okay, you lost me about halfway through that... could you perhaps > >> describe the problem from the beginning, exactly what you're trying to do? > > > > A kernel compiled with VMI enabled may run on a non-VMI platform. If > > that is the case, the fixmap should not be relocated. If however, a VMI > > ROM is found, we need to hijack up to 64-MB of linear address space from > > the top of memory down. This means moving the fixmap down by the same > > amount. > > > > I take it there are no alternatives other than putting this at the end > of memory? Nope, it must be in an area allowing for segmentation protection, while keeping the kernel on zero-based segments; that means only the end of linear address space is sufficient. > Realistically speaking, any (virtual) machine which does *not* have a > full complement of lowmem (i.e. less than 896 MB in the common case) > will not suffer significatly from losing a few megabytes of address space. Yes, the reason to make the fixmap moveable is to allow as much address space as possible for big memory (physical) machines. -- 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/