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 5627DC433DF for ; Fri, 12 Jun 2020 10:34:39 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 35CB320801 for ; Fri, 12 Jun 2020 10:34:39 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726289AbgFLKeh convert rfc822-to-8bit (ORCPT ); Fri, 12 Jun 2020 06:34:37 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:47874 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725911AbgFLKeg (ORCPT ); Fri, 12 Jun 2020 06:34:36 -0400 Received: from Galois.linutronix.de (Galois.linutronix.de [IPv6:2a0a:51c0:0:12e:550::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 3C1C3C03E96F for ; Fri, 12 Jun 2020 03:34:36 -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 1jjh0t-0001u4-Ig; Fri, 12 Jun 2020 12:34:19 +0200 Received: by nanos.tec.linutronix.de (Postfix, from userid 1000) id AD1CA100F5A; Fri, 12 Jun 2020 12:34:18 +0200 (CEST) From: Thomas Gleixner To: Andy Lutomirski Cc: Andy Lutomirski , Peter Zijlstra , Naresh Kamboju , open list , X86 ML , cj.chengjian@huawei.com, Arnaldo Carvalho de Melo , Ingo Molnar , "H. Peter Anvin" , Borislav Petkov , Minchan Kim , Andrew Morton , Michel Lespinasse , lkft-triage@lists.linaro.org, Dave Hansen Subject: Re: Perf: WARNING: arch/x86/entry/common.c:624 idtentry_exit_cond_rcu+0x92/0xc0 In-Reply-To: <8DD3180E-0E69-4FD6-92C3-311AAB3F688F@amacapital.net> References: <87imfwd5f6.fsf@nanos.tec.linutronix.de> <8DD3180E-0E69-4FD6-92C3-311AAB3F688F@amacapital.net> Date: Fri, 12 Jun 2020 12:34:18 +0200 Message-ID: <87d064d13p.fsf@nanos.tec.linutronix.de> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 8BIT 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 Andy Lutomirski writes: >> On Jun 12, 2020, at 2:01 AM, Thomas Gleixner wrote: >> There is no IST on 32bit, never was. We do software stack switching for >> device interrupts, but that's a different story. >> > > DEFINE_IDTENTRY does the idtentry_enter_cond_rcu() dance, which isn’t > intended to be safe from NMI context. It should probably map to > DEFINE_IDTENTRY_RAW() instead. The specific issue is that NMI ends up > there, and at least DEFINE_IDTENTRY_NMI should be raw. Yes, you are right. That's clearly broken. > I haven’t tried this at all, nor have I dug through all the users of > these macros to check what they expect. Perhaps we should not have > the _IST one defined at all on 32 bit and rename it to > DEFINE_IDTENTRY_IST_RAW on 64 bit to make it more clear what’s going > on when reading the C code. Let me go over it with a fine comb. > Or maybe I’m too sleepy and I’m nuts. But I don’t think I am. /me politely refrains from commenting