Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751958Ab2FMDaL (ORCPT ); Tue, 12 Jun 2012 23:30:11 -0400 Received: from terminus.zytor.com ([198.137.202.10]:48177 "EHLO mail.zytor.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751156Ab2FMDaK (ORCPT ); Tue, 12 Jun 2012 23:30:10 -0400 Message-ID: <4FD80923.1060807@zytor.com> Date: Tue, 12 Jun 2012 20:29:39 -0700 From: "H. Peter Anvin" User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:12.0) Gecko/20120430 Thunderbird/12.0.1 MIME-Version: 1.0 To: Kamezawa Hiroyuki CC: Wen Congyang , rob@landley.net, tglx@linutronix.de, Ingo Molnar , x86@kernel.org, "linux-kernel@vger.kernel.org" , bhelgaas@google.com Subject: Re: [PATCH 1/2 v2] x86: add max_addr boot option References: <4FD5AFF2.3040306@cn.fujitsu.com> <4FD65FD4.4060705@zytor.com> <4FD6E101.3010106@cn.fujitsu.com> <4FD7F937.2010101@jp.fujitsu.com> In-Reply-To: <4FD7F937.2010101@jp.fujitsu.com> X-Enigmail-Version: 1.4.2 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1409 Lines: 36 On 06/12/2012 07:21 PM, Kamezawa Hiroyuki wrote: > > But now, we know mem= boot option is buggy....it acts as max_addr= > option, we have concerns that 'someone may fix mem= option as sane as ia64. because > it's buggy". > > We'd like to fix mem= boot option by ourselves and preserve old behavior > with max_addr= boot option, which ia64 has. > Now I'm *really* confused. Realistically, there is no point in the old mem= behavior of assuming a contiguous chunk of memory up to that point; it simply doesn't match how modern hardware is constructed. Your notion that ia64 is "sane" is probably more of "outdated" in my opinion. As such, the current behavior for mem= seems like the right thing and the change was intentional (not to mention has been in place since kernel 2.5.65, back in 2003); it also solves your requirements. If you are concerned about it, it would make more sense to make sure it is documented as intentional. In fact, it looks like IA64 introduced a divergence when the max_addr= patch was introduced in 2004. You're basically proposing the same divergence for x86 now; talk about having the tail wag the dog. Sorry. NAK. -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/