Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1764818AbZDCM2n (ORCPT ); Fri, 3 Apr 2009 08:28:43 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1764500AbZDCM2V (ORCPT ); Fri, 3 Apr 2009 08:28:21 -0400 Received: from mx3.mail.elte.hu ([157.181.1.138]:44340 "EHLO mx3.mail.elte.hu" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1764198AbZDCM2U (ORCPT ); Fri, 3 Apr 2009 08:28:20 -0400 Date: Fri, 3 Apr 2009 14:26:54 +0200 From: Ingo Molnar To: Avi Kivity Cc: Masami Hiramatsu , "H. Peter Anvin" , Frederic Weisbecker , Steven Rostedt , Ananth N Mavinakayanahalli , Andrew Morton , Andi Kleen , Jim Keniston , kvm@vger.kernel.org, systemtap-ml , LKML Subject: Re: [PATCH -tip 0/6 V4] tracing: kprobe-based event tracer Message-ID: <20090403122654.GA19451@elte.hu> References: <49D4F4B5.9040107@redhat.com> <20090403112639.GC31399@elte.hu> <49D5F80B.7000305@redhat.com> <20090403121202.GI31399@elte.hu> <49D5FE42.5080100@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <49D5FE42.5080100@redhat.com> User-Agent: Mutt/1.5.18 (2008-05-17) X-ELTE-VirusStatus: clean 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 Content-Length: 1615 Lines: 39 * Avi Kivity wrote: > Ingo Molnar wrote: >>> kvm has three requirements not needed by kprobes: >>> - it wants to execute instructions, not just decode them, including >>> generating faults where appropriate >>> - it is performance critical >>> - it needs to support 16-bit, 32-bit, and 64-bit instructions simultaneously >>> >>> If an arch/x86/ decoder/emulator gives me these I'll gladly switch >>> to it. x86_emulate.c is high on my list of most disliked code. >>> >> >> Well, this has to be driven from the KVM side as the kprobes use >> will only be for decoding so if it's modified from the kprobes >> side the KVM-only functionality might regress. >> >> So ... we can do the library decoder for kprobes purposes, and >> someone versed in the KVM emulator can then combine the two. > > Problem is, anyone versed in the kvm emulator will want to run as > far away from this work as possible. Are you suggesting that the KVM emulator should never have been merged in the first place? ;-) Anyway, we'll make sure the kprobes/library decoder is as clean as possible - so it ought to be hackable and extensible without the risk of permanent brain damage. Mmiotrace and kmemcheck has decoding smarts too, and i think the sw-breakpoint injection code of KGDB could use it as well - so there's broader utility in all this. Ingo -- 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/