From mboxrd@z Thu Jan  1 00:00:00 1970
Return-Path: <linux-kernel-owner@vger.kernel.org>
Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand
	id S1753435AbbLJUvq (ORCPT <rfc822;w@1wt.eu>);
	Thu, 10 Dec 2015 15:51:46 -0500
Received: from www.linutronix.de ([62.245.132.108]:36752 "EHLO
	Galois.linutronix.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org
	with ESMTP id S1751047AbbLJUu0 (ORCPT
	<rfc822;linux-kernel@vger.kernel.org>);
	Thu, 10 Dec 2015 15:50:26 -0500
Date: Thu, 10 Dec 2015 21:49:33 +0100 (CET)
From: Thomas Gleixner <tglx@linutronix.de>
To: Andy Lutomirski <luto@amacapital.net>
cc: Jeff Merkey <linux.mdb@gmail.com>, LKML <linux-kernel@vger.kernel.org>,
        Ingo Molnar <mingo@redhat.com>, "H. Peter Anvin" <hpa@zytor.com>,
        X86 ML <x86@kernel.org>, Peter Zijlstra <peterz@infradead.org>,
        Andy Lutomirski <luto@kernel.org>,
        Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com>,
        Steven Rostedt <rostedt@goodmis.org>, Borislav Petkov <bp@alien8.de>,
        Jiri Olsa <jolsa@kernel.org>
Subject: Re: [PATCH 1/1] Fix int1 recursion when no perf_bp_event is
 registeredy
In-Reply-To: <CALCETrUaWxqyuyE2FqCs0ULPBdKMwCPtaoneyt4yBA8r5a5=yQ@mail.gmail.com>
Message-ID: <alpine.DEB.2.11.1512102050290.3623@nanos>
References: <CAO6TR8W1ViJonskb0eObG+THObpabh909ob0Oz_8LAvNMuOPmA@mail.gmail.com> <alpine.DEB.2.11.1512101942470.3623@nanos> <CALCETrUaWxqyuyE2FqCs0ULPBdKMwCPtaoneyt4yBA8r5a5=yQ@mail.gmail.com>
User-Agent: Alpine 2.11 (DEB 23 2013-08-11)
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
List-ID: <linux-kernel.vger.kernel.org>
X-Mailing-List: linux-kernel@vger.kernel.org

On Thu, 10 Dec 2015, Andy Lutomirski wrote:
> On brief inspection, this smells like a microcode bug.  Can you send
> /proc/cpuinfo output?
> 
> If this is the issue, I'm not sure we want to be in the business of
> working around localized microcode bugs and, if we do, then I think we
> should explicitly detect the bug and log about it.

I think we should handle such stuff gracefully. Yes, we should log it
and we also should check what the contents of the debug registers are.

If dr7 has a break point enabled w/o perf having one installed then we
know that someone did a horrible hackery ....

Thanks,

	tglx