From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2993126AbXCIVFf (ORCPT ); Fri, 9 Mar 2007 16:05:35 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S2993130AbXCIVFf (ORCPT ); Fri, 9 Mar 2007 16:05:35 -0500 Received: from mx2.mail.elte.hu ([157.181.151.9]:41366 "EHLO mx2.mail.elte.hu" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2993126AbXCIVFe (ORCPT ); Fri, 9 Mar 2007 16:05:34 -0500 Date: Fri, 9 Mar 2007 22:04:30 +0100 From: Ingo Molnar To: Linus Torvalds Cc: Jeremy Fitzhardinge , Zachary Amsden , Thomas Gleixner , john stultz , akpm@linux-foundation.org, LKML , Rusty Russell , Andi Kleen , Chris Wright , Alan Cox Subject: Re: ABI coupling to hypervisors via CONFIG_PARAVIRT Message-ID: <20070309210430.GA14905@elte.hu> References: <20070309180230.GA17988@elte.hu> <20070309192420.GA27747@elte.hu> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.4.2.2i X-ELTE-VirusStatus: clean X-ELTE-SpamScore: -2.0 X-ELTE-SpamLevel: X-ELTE-SpamCheck: no X-ELTE-SpamVersion: ELTE 2.0 X-ELTE-SpamCheck-Details: score=-2.0 required=5.9 tests=BAYES_00 autolearn=no SpamAssassin version=3.1.7 -2.0 BAYES_00 BODY: Bayesian spam probability is 0 to 1% [score: 0.0000] Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org * Linus Torvalds wrote: > So please > > - point out things that are badly done. [...] the thing badly done is fundamental and it trumps any other small technological detail complaint i have, because it affects the development and maintainance model: to promise backwards compatibility to 4-5 different hypervisors, using separate ABIs for each. /One/ such ABI would be complex enough to maintain IMO. ( if there is no backwards compatibility promise then i have zero complaints: then paravirt_ops + the hypercall just becomes another API internal to Linux that we can improve at will. But that is not realistic: if we provide CONFIG_VMI today, people will expect to have CONFIG_VMI in the future too. ) as i said in the very, very first email about this topic: /one/ new ABI towards hypervisors should be introduced step by step, and via concensus across hypervisors. We should treat the hypercall ABI very similar to the system call ABI: the system call ABI is largely based on a concensus between applications. [ i think apic_write() granularity is bad too - but that is a small technical issue, dwarved by the ABI issues that impact the development model IMO. ] Ingo