From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752783AbZKHNF2 (ORCPT ); Sun, 8 Nov 2009 08:05:28 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1751951AbZKHNF1 (ORCPT ); Sun, 8 Nov 2009 08:05:27 -0500 Received: from mx3.mail.elte.hu ([157.181.1.138]:40407 "EHLO mx3.mail.elte.hu" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751344AbZKHNF1 (ORCPT ); Sun, 8 Nov 2009 08:05:27 -0500 Date: Sun, 8 Nov 2009 14:05:21 +0100 From: Ingo Molnar To: Avi Kivity Cc: Gleb Natapov , kvm@vger.kernel.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org, "H. Peter Anvin" , Thomas Gleixner , Fr??d??ric Weisbecker Subject: Re: [PATCH 02/11] Add "handle page fault" PV helper. Message-ID: <20091108130521.GA29728@elte.hu> References: <20091102092214.GB8933@elte.hu> <20091102160410.GF27911@redhat.com> <20091102161248.GB15423@elte.hu> <20091102162234.GH27911@redhat.com> <20091102162941.GC14544@elte.hu> <20091102174208.GJ27911@redhat.com> <20091108113654.GO11372@elte.hu> <4AF6BCE5.3030701@redhat.com> <20091108125135.GA13099@elte.hu> <4AF6C112.4010601@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <4AF6C112.4010601@redhat.com> User-Agent: Mutt/1.5.20 (2009-08-17) X-ELTE-SpamScore: -1.5 X-ELTE-SpamLevel: X-ELTE-SpamCheck: no X-ELTE-SpamVersion: ELTE 2.0 X-ELTE-SpamCheck-Details: score=-1.5 required=5.9 tests=BAYES_00 autolearn=no SpamAssassin version=3.2.5 -1.5 BAYES_00 BODY: Bayesian spam probability is 0 to 1% [score: 0.0000] Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org * Avi Kivity wrote: > On 11/08/2009 02:51 PM, Ingo Molnar wrote: > >>Maybe we should generalize paravirt-ops patching in case if (x) f() is > >>deemed too expensive. > >Yes, that's a nice idea. We have quite a number of 'conditional > >callbacks' in various critical paths that could be made lighter via such > >a technique. > > > > It would also free new callbacks from the 'it increases overhead > > even if unused' criticism and made it easier to add them. > > We can take the "immediate values" infrastructure as a first step. Has > that been merged? No, there were doubts about whether patching in live instructions like that is safe on all CPU types. Ingo