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=-2.6 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_PASS, USER_AGENT_MUTT 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 30B8EC43387 for ; Fri, 18 Jan 2019 10:24:52 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id F2D932087E for ; Fri, 18 Jan 2019 10:24:51 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=alien8.de header.i=@alien8.de header.b="YEzc1aPy" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727143AbfARKYu (ORCPT ); Fri, 18 Jan 2019 05:24:50 -0500 Received: from mail.skyhub.de ([5.9.137.197]:59672 "EHLO mail.skyhub.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726880AbfARKYt (ORCPT ); Fri, 18 Jan 2019 05:24:49 -0500 Received: from zn.tnic (p200300EC2BCB1B0039C8CE17CD8BEE66.dip0.t-ipconnect.de [IPv6:2003:ec:2bcb:1b00:39c8:ce17:cd8b:ee66]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.skyhub.de (SuperMail on ZX Spectrum 128k) with ESMTPSA id 038BF1EC0242; Fri, 18 Jan 2019 11:24:47 +0100 (CET) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=alien8.de; s=dkim; t=1547807088; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:in-reply-to:in-reply-to: references:references; bh=rHjjAoPZ5WzSd01uaObMcFJeh6ALPK1Gb/WHY2w5Pz8=; b=YEzc1aPy3mXS3qxIvYcxq0E0DAJLq2Su44Fw1dsitFo2thcK2+srOrcFwxCWb+FW9zfvGD Mp0RL3mPPcq42t6gQeBz44emTDHXFAiNCAUHtLZ9ASqvYKiynA5XIoaZfnSQU55h/J64oH /g6G2YYqbOWCKCKDI2x8qQqVzpNWh+w= Date: Fri, 18 Jan 2019 11:24:27 +0100 From: Borislav Petkov To: Peter Zijlstra Cc: James Morse , Waiman Long , Zhenzhong Duan , LKML , SRINIVAS , Steven Rostedt Subject: Re: Question about qspinlock nest Message-ID: <20190118102427.GA622@zn.tnic> References: <910e9fb6-d0df-4711-fe2b-244b3c20eb82@redhat.com> <20190110201217.GH2861@worktop.programming.kicks-ass.net> <20190114131613.GB10486@hirez.programming.kicks-ass.net> <830db851-d5cb-4081-8d72-e3f3a0a282df@arm.com> <20190118100229.GB27931@hirez.programming.kicks-ass.net> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <20190118100229.GB27931@hirez.programming.kicks-ass.net> User-Agent: Mutt/1.10.1 (2018-07-13) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, Jan 18, 2019 at 11:02:29AM +0100, Peter Zijlstra wrote: > Well, x86 too has multiple non-maskable vectors, and afaik only the > actual NMI vector is covered in tricky. But our MCE vector is > non-maskable too (and I have vague memories of there being more). > > Boris, Rostedt, WTH happens if our MCE code goes and hits a #BP ? (not > unlikely with this proliferation of self-modifying code) > > Anyway, the idea is that they can indeed not interrupt themselves, but I > would not be surprised if the whole MCE thing is riddled with fail (on > x86). As we talked on IRC: we'll apply a mixture of "So don't do that then!" hints i.e., kprobing MCE code etc, and fix the issues like the schedule_work() invocation. In general, I'd like to make/keep the #MC handler as simple and as idiot-proof as possible. -- Regards/Gruss, Boris. Good mailing practices for 400: avoid top-posting and trim the reply.