From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-0.8 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 4926FC433E0 for ; Wed, 20 May 2020 20:10:13 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 282FF2075F for ; Wed, 20 May 2020 20:10:13 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727880AbgETUKM (ORCPT ); Wed, 20 May 2020 16:10:12 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:53312 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726853AbgETUKM (ORCPT ); Wed, 20 May 2020 16:10:12 -0400 Received: from Galois.linutronix.de (Galois.linutronix.de [IPv6:2a0a:51c0:0:12e:550::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id DA151C061A0E for ; Wed, 20 May 2020 13:10:11 -0700 (PDT) Received: from p5de0bf0b.dip0.t-ipconnect.de ([93.224.191.11] helo=nanos.tec.linutronix.de) by Galois.linutronix.de with esmtpsa (TLS1.2:DHE_RSA_AES_256_CBC_SHA256:256) (Exim 4.80) (envelope-from ) id 1jbV27-0002It-7H; Wed, 20 May 2020 22:09:46 +0200 Received: by nanos.tec.linutronix.de (Postfix, from userid 1000) id A629E100C99; Wed, 20 May 2020 22:09:42 +0200 (CEST) From: Thomas Gleixner To: Peter Zijlstra Cc: LKML , x86@kernel.org, "Paul E. McKenney" , Andy Lutomirski , Alexandre Chartre , Frederic Weisbecker , Paolo Bonzini , Sean Christopherson , Masami Hiramatsu , Petr Mladek , Steven Rostedt , Joel Fernandes , Boris Ostrovsky , Juergen Gross , Brian Gerst , Mathieu Desnoyers , Josh Poimboeuf , Will Deacon , Tom Lendacky , Wei Liu , Michael Kelley , Jason Chen CJ , Zhao Yakui Subject: Re: [patch V6 04/37] x86: Make hardware latency tracing explicit In-Reply-To: <20200518080814.GJ2940@hirez.programming.kicks-ass.net> References: <20200515234547.710474468@linutronix.de> <20200515235124.783722942@linutronix.de> <20200518080133.GI2940@hirez.programming.kicks-ass.net> <874ksdzmzf.fsf@nanos.tec.linutronix.de> <20200518080814.GJ2940@hirez.programming.kicks-ass.net> Date: Wed, 20 May 2020 22:09:42 +0200 Message-ID: <87imgqv055.fsf@nanos.tec.linutronix.de> MIME-Version: 1.0 Content-Type: text/plain X-Linutronix-Spam-Score: -1.0 X-Linutronix-Spam-Level: - X-Linutronix-Spam-Status: No , -1.0 points, 5.0 required, ALL_TRUSTED=-1,SHORTCIRCUIT=-0.0001 Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Peter Zijlstra writes: > On Mon, May 18, 2020 at 10:05:56AM +0200, Thomas Gleixner wrote: >> Peter Zijlstra writes: >> > On Sat, May 16, 2020 at 01:45:51AM +0200, Thomas Gleixner wrote: >> >> --- a/arch/x86/kernel/nmi.c >> >> +++ b/arch/x86/kernel/nmi.c >> >> @@ -334,6 +334,7 @@ static noinstr void default_do_nmi(struc >> >> __this_cpu_write(last_nmi_rip, regs->ip); >> >> >> >> instrumentation_begin(); >> >> + ftrace_nmi_handler_enter(); >> >> >> >> handled = nmi_handle(NMI_LOCAL, regs); >> >> __this_cpu_add(nmi_stats.normal, handled); >> >> @@ -420,6 +421,7 @@ static noinstr void default_do_nmi(struc >> >> unknown_nmi_error(reason, regs); >> >> >> >> out: >> >> + ftrace_nmi_handler_exit(); >> >> instrumentation_end(); >> >> } >> > >> > Yeah, so I'm confused about this and the previous patch too. Why not >> > do just this? Remove that ftrace_nmi_handler.* crud from >> > nmi_{enter,exit}() and stick it here? Why do we needs the >> > nmi_{enter,exit}_notrace() thing? >> >> Because you then have to fixup _all_ architectures which use >> nmi_enter/exit(). > > We probably have to anyway. But I can do that later I suppose. Second thoughts. For #DB and #INT3 we can just keep nmi_enter(), needs just annotation in nmi_enter() around that trace muck. For #NMI and #MCE I rather avoid the early trace call and do it once we have reached "stable" state, i.e. avoid it in the whole nested NMI mess. Thanks, tglx