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=-1.0 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_PASS autolearn=ham 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 F356BC4360F for ; Thu, 4 Apr 2019 17:32:18 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id CE26B20820 for ; Thu, 4 Apr 2019 17:32:18 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729456AbfDDRcR (ORCPT ); Thu, 4 Apr 2019 13:32:17 -0400 Received: from Galois.linutronix.de ([146.0.238.70]:46114 "EHLO Galois.linutronix.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727562AbfDDRcR (ORCPT ); Thu, 4 Apr 2019 13:32:17 -0400 Received: from p5492e2fc.dip0.t-ipconnect.de ([84.146.226.252] helo=nanos) by Galois.linutronix.de with esmtpsa (TLS1.2:DHE_RSA_AES_256_CBC_SHA256:256) (Exim 4.80) (envelope-from ) id 1hC6DY-00074s-FU; Thu, 04 Apr 2019 19:32:00 +0200 Date: Thu, 4 Apr 2019 19:31:59 +0200 (CEST) From: Thomas Gleixner To: Fenghua Yu cc: Ingo Molnar , Borislav Petkov , H Peter Anvin , Dave Hansen , Paolo Bonzini , Ashok Raj , Peter Zijlstra , Kalle Valo , Xiaoyao Li , Michael Chan , Ravi V Shankar , linux-kernel , x86 , linux-wireless@vger.kernel.org, netdev@vger.kernel.org, kvm@vger.kernel.org Subject: Re: [PATCH v6 10/20] x86/split_lock: Handle #AC exception for split lock In-Reply-To: <1554326526-172295-11-git-send-email-fenghua.yu@intel.com> Message-ID: References: <1554326526-172295-1-git-send-email-fenghua.yu@intel.com> <1554326526-172295-11-git-send-email-fenghua.yu@intel.com> User-Agent: Alpine 2.21 (DEB 202 2017-01-01) MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII 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 On Wed, 3 Apr 2019, Fenghua Yu wrote: > +dotraplinkage void do_alignment_check(struct pt_regs *regs, long error_code) > +{ > + unsigned int trapnr = X86_TRAP_AC; > + char str[] = "alignment check"; > + int signr = SIGBUS; > + > + RCU_LOCKDEP_WARN(!rcu_is_watching(), "entry code didn't wake RCU"); > + > + /* > + * WARN*()s end up here; fix them up before we call the > + * notifier chain. > + */ How exactly is WARN*() ending up here? > + if (!user_mode(regs) && fixup_bug(regs, trapnr)) And that fixup_bug() check does what? int fixup_bug(struct pt_regs *regs, int trapnr) { if (trapnr != X86_TRAP_UD) return 0; Copy and paste from do_error_trap() .... > + return; > + > + if (notify_die(DIE_TRAP, str, regs, error_code, trapnr, signr) == > + NOTIFY_STOP) > + return; > + > + cond_local_irq_enable(regs); > + if (!user_mode(regs) && > + static_cpu_has(X86_FEATURE_SPLIT_LOCK_DETECT)) { > + /* > + * Only split lock can generate #AC from kernel at this point. > + * Warn and disable split lock detection on this CPU. The > + * faulting instruction will be executed without generating > + * another #AC fault. User needs to check the warning and > + * fix the split lock issue in the faulting instruction. "User needs to check the warning and fix the issue ..." I'm looking forward to all the fixes from Joe Users. Please remove that sentence. It's useless. Users report warnings if at all and the kernel developers who actually look at them surely don't need an advice like that. Thanks, tglx