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=-3.7 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED 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 A1C55C2D0FA for ; Tue, 12 May 2020 22:23:11 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 5703E20747 for ; Tue, 12 May 2020 22:23:11 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1731651AbgELWXK (ORCPT ); Tue, 12 May 2020 18:23:10 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:55460 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-FAIL-OK-FAIL) by vger.kernel.org with ESMTP id S1727971AbgELWXF (ORCPT ); Tue, 12 May 2020 18:23:05 -0400 Received: from Galois.linutronix.de (Galois.linutronix.de [IPv6:2a0a:51c0:0:12e:550::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 1659CC061A0C for ; Tue, 12 May 2020 15:23:05 -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 1jYdI7-0004c1-P6; Wed, 13 May 2020 00:22:24 +0200 Received: from nanos.tec.linutronix.de (localhost [IPv6:::1]) by nanos.tec.linutronix.de (Postfix) with ESMTP id 4A9F91001FC; Wed, 13 May 2020 00:22:23 +0200 (CEST) Message-Id: <20200512213809.784331304@linutronix.de> User-Agent: quilt/0.65 Date: Tue, 12 May 2020 23:01:03 +0200 From: Thomas Gleixner To: LKML Cc: 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 , "Peter Zijlstra (Intel)" Subject: [patch V5 04/38] x86: Make hardware latency tracing explicit References: <20200512210059.056244513@linutronix.de> MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-transfer-encoding: 8-bit 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 The hardware latency tracer calls into trace_sched_clock and ends up in various instrumentable functions which is problemeatic vs. the kprobe handling especially the text poke machinery. It's invoked from nmi_enter/exit(), i.e. non-instrumentable code. Use nmi_enter/exit_notrace() instead. These variants do not invoke the hardware latency tracer which avoids chasing down complex callchains to make them non-instrumentable. The real interesting measurement is the actual NMI handler. Add an explicit invocation for the hardware latency tracer to it. #DB and #BP are uninteresting as they really should not be in use when analzying hardware induced latencies. If #DF hits, hardware latency is definitely not interesting anymore and in case of a machine check the hardware latency is not the most troublesome issue either. Signed-off-by: Thomas Gleixner --- V5: New patch --- arch/x86/kernel/cpu/mce/core.c | 4 ++-- arch/x86/kernel/nmi.c | 6 ++++-- arch/x86/kernel/traps.c | 10 +++++----- 3 files changed, 11 insertions(+), 9 deletions(-) --- a/arch/x86/kernel/cpu/mce/core.c +++ b/arch/x86/kernel/cpu/mce/core.c @@ -1916,7 +1916,7 @@ static __always_inline void exc_machine_ mce_check_crashing_cpu()) return; - nmi_enter(); + nmi_enter_notrace(); /* * The call targets are marked noinstr, but objtool can't figure * that out because it's an indirect call. Annotate it. @@ -1924,7 +1924,7 @@ static __always_inline void exc_machine_ instrumentation_begin(); machine_check_vector(regs); instrumentation_end(); - nmi_exit(); + nmi_exit_notrace(); } static __always_inline void exc_machine_check_user(struct pt_regs *regs) --- 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_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_exit(); instrumentation_end(); } @@ -536,14 +538,14 @@ DEFINE_IDTENTRY_NMI(exc_nmi) } #endif - nmi_enter(); + nmi_enter_notrace(); inc_irq_stat(__nmi_count); if (!ignore_nmis) default_do_nmi(regs); - nmi_exit(); + nmi_exit_notrace(); #ifdef CONFIG_X86_64 if (unlikely(this_cpu_read(update_debug_stack))) { --- a/arch/x86/kernel/traps.c +++ b/arch/x86/kernel/traps.c @@ -378,7 +378,7 @@ DEFINE_IDTENTRY_DF(exc_double_fault) } #endif - nmi_enter(); + nmi_enter_notrace(); instrumentation_begin(); notify_die(DIE_TRAP, str, regs, error_code, X86_TRAP_DF, SIGSEGV); @@ -624,11 +624,11 @@ DEFINE_IDTENTRY_RAW(exc_int3) instrumentation_end(); idtentry_exit(regs); } else { - nmi_enter(); + nmi_enter_notrace(); instrumentation_begin(); do_int3(regs); instrumentation_end(); - nmi_exit(); + nmi_exit_notrace(); } } @@ -827,7 +827,7 @@ static void noinstr handle_debug(struct static __always_inline void exc_debug_kernel(struct pt_regs *regs, unsigned long dr6) { - nmi_enter(); + nmi_enter_notrace(); /* * The SDM says "The processor clears the BTF flag when it * generates a debug exception." Clear TIF_BLOCKSTEP to keep @@ -849,7 +849,7 @@ static __always_inline void exc_debug_ke if (dr6) handle_debug(regs, dr6, false); - nmi_exit(); + nmi_exit_notrace(); } static __always_inline void exc_debug_user(struct pt_regs *regs,