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,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 F1BE4C433E0 for ; Wed, 20 May 2020 12:35:39 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id CB7F620758 for ; Wed, 20 May 2020 12:35:39 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727003AbgETMfj (ORCPT ); Wed, 20 May 2020 08:35:39 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:38414 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726224AbgETMfi (ORCPT ); Wed, 20 May 2020 08:35:38 -0400 Received: from Galois.linutronix.de (Galois.linutronix.de [IPv6:2a0a:51c0:0:12e:550::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 88D98C061A0E for ; Wed, 20 May 2020 05:35:38 -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 1jbNwD-0007ph-03; Wed, 20 May 2020 14:35:09 +0200 Received: by nanos.tec.linutronix.de (Postfix, from userid 1000) id 4C094100C99; Wed, 20 May 2020 14:35:08 +0200 (CEST) From: Thomas Gleixner To: Andy Lutomirski Cc: Andy Lutomirski , LKML , X86 ML , "Paul E. McKenney" , 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: Re: [patch V6 07/37] x86/entry: Provide helpers for execute on irqstack In-Reply-To: References: <20200515234547.710474468@linutronix.de> <20200515235125.110889386@linutronix.de> <87o8qkvm03.fsf@nanos.tec.linutronix.de> Date: Wed, 20 May 2020 14:35:08 +0200 Message-ID: <871rne6ayr.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 Andy Lutomirski writes: > On Mon, May 18, 2020 at 4:53 PM Thomas Gleixner wrote: >> >> Andy Lutomirski writes: >> > Actually, I revoke my ack. Can you make one of two changes: >> > >> > Option A: Add an assertion to run_on_irqstack to verify that irq_count >> > was -1 at the beginning? I suppose this also means you could just >> > explicitly write 0 instead of adding and subtracting. >> > >> > Option B: Make run_on_irqstack() just call the function on the current >> > stack if we're already on the irq stack. >> > >> > Right now, it's too easy to mess up and not verify the right >> > precondition before calling run_on_irqstack(). >> > >> > If you choose A, perhaps add a helper to do the if(irq_needs_irqstack) >> > dance so that users can just do: >> > >> > run_on_irqstack_if_needed(...); >> > >> > instead of checking everything themselves. >> >> I'll have a look tomorrow morning with brain awake. > > Also, reading more of the series, I suspect that asm_call_on_stack is > logically in the wrong section or that the noinstr stuff is otherwise > not quite right. I think that objtool should not accept > run_on_irqstack() from noinstr code. See followups on patch 10. It's in entry.text which is non-instrumentable as well.