Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752421AbaB1VGm (ORCPT ); Fri, 28 Feb 2014 16:06:42 -0500 Received: from cdptpa-outbound-snat.email.rr.com ([107.14.166.232]:54922 "EHLO cdptpa-oedge-vip.email.rr.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1752129AbaB1VGk (ORCPT ); Fri, 28 Feb 2014 16:06:40 -0500 Date: Fri, 28 Feb 2014 16:06:38 -0500 From: Steven Rostedt To: Peter Zijlstra Cc: "H. Peter Anvin" , Vince Weaver , Linux Kernel , Ingo Molnar , Jiri Olsa , Arnaldo Carvalho de Melo Subject: Re: perf_fuzzer compiled for x32 causes reboot Message-ID: <20140228160638.3b045dbc@gandalf.local.home> In-Reply-To: <20140228205638.GD14089@laptop.programming.kicks-ass.net> References: <530FC1C6.5040209@zytor.com> <20140227215726.7018c861@gandalf.local.home> <20140228092341.12a40f7c@gandalf.local.home> <1c583986-74f8-4829-883b-390dc49ddabb@email.android.com> <20140228154026.GH9987@twins.programming.kicks-ass.net> <5310B60F.30806@zytor.com> <20140228112946.1f194397@gandalf.local.home> <20140228205638.GD14089@laptop.programming.kicks-ass.net> X-Mailer: Claws Mail 3.9.3 (GTK+ 2.24.22; x86_64-pc-linux-gnu) MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit X-RR-Connecting-IP: 107.14.168.130:25 X-Cloudmark-Score: 0 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, 28 Feb 2014 21:56:38 +0100 Peter Zijlstra wrote: > Like already said; _trace is an absolutely abysmal name. Also you > _really_ don't want an unconditional CR2 write in there, that's just > stupidly expensive. But a read isn't. Which is why we only do a write if the copy caused a page fault (which is already expensive). The proposed patch will have: if (cr2 != read_cr2()) write_cr2(cr2); > > Also, this function is called a _LOT_ under certain workloads, I don't > know how cheap a CR2 read is, but it had better be really cheap. That's a HPA question. -- Steve -- 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/