From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S933416AbXLQAI0 (ORCPT ); Sun, 16 Dec 2007 19:08:26 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1759499AbXLQAIP (ORCPT ); Sun, 16 Dec 2007 19:08:15 -0500 Received: from ogre.sisk.pl ([217.79.144.158]:49699 "EHLO ogre.sisk.pl" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1758988AbXLQAIN (ORCPT ); Sun, 16 Dec 2007 19:08:13 -0500 From: "Rafael J. Wysocki" To: Ingo Molnar Subject: Re: [PATCH 4/8] unify paravirt parts of system.h Date: Mon, 17 Dec 2007 01:27:29 +0100 User-Agent: KMail/1.9.6 (enterprise 20070904.708012) Cc: Pavel Machek , Andi Kleen , Avi Kivity , Glauber de Oliveira Costa , linux-kernel@vger.kernel.org, akpm@linux-foundation.org, glommer@gmail.com, tglx@linutronix.de, ehabkost@redhat.com, jeremy@goop.org, anthony@codemonkey.ws, virtualization@lists.linux-foundation.org, rusty@rustcorp.com.au, chrisw@sous-sol.org, rostedt@goodmis.org, hpa@zytor.com References: <11967843881946-git-send-email-gcosta@redhat.com> <20071205163017.GA4756@ucw.cz> <20071215131723.GF9720@elte.hu> In-Reply-To: <20071215131723.GF9720@elte.hu> MIME-Version: 1.0 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: 7bit Content-Disposition: inline Message-Id: <200712170127.31615.rjw@sisk.pl> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Saturday, 15 of December 2007, Ingo Molnar wrote: > > * Pavel Machek wrote: > > > > Linux never uses that register. The only user is suspend > > > save/restore, but that' bogus because it wasn't ever initialized by > > > Linux in the first place. It could be probably all safely removed. > > > > It probably is safe to remove... but we currently support '2.8.95 > > kernel loads/resumes 2.6.24 image'... which would break if 2.8 uses > > cr8. > > > > So please keep it if it is not a big problem. > > hm, so __save_processor_state() is in essence an ABI? Could you please > also send a patch that documents this prominently, in the structure > itself? Hmm, I'm not sure if it really is an ABI part. It doesn't communicate anything outside of the kernel in which it is defined. The problem is, though, that if kernel A is used for resuming kernel B, and kernel B doesn't save/restore everything it will need after the resume, then things will break if kernel A modifies that. So, yes, we'll need to document that explicitly. Greetings, Rafael