linux-kernel - Re: [PATCH 1/1] Fix int1 recursion when no perf_bp

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Message-ID: <alpine.DEB.2.11.1512102050290.3623@nanos>
Date:	Thu, 10 Dec 2015 21:49:33 +0100 (CET)
From:	Thomas Gleixner <tglx@...utronix.de>
To:	Andy Lutomirski <luto@...capital.net>
cc:	Jeff Merkey <linux.mdb@...il.com>,
	LKML <linux-kernel@...r.kernel.org>,
	Ingo Molnar <mingo@...hat.com>,
	"H. Peter Anvin" <hpa@...or.com>, X86 ML <x86@...nel.org>,
	Peter Zijlstra <peterz@...radead.org>,
	Andy Lutomirski <luto@...nel.org>,
	Masami Hiramatsu <masami.hiramatsu.pt@...achi.com>,
	Steven Rostedt <rostedt@...dmis.org>,
	Borislav Petkov <bp@...en8.de>, Jiri Olsa <jolsa@...nel.org>
Subject: Re: [PATCH 1/1] Fix int1 recursion when no perf_bp_event is
 registeredy

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


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