linux-kernel - Re: [RFC] x86_64: A real proposal for iret-less return to kernel

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Message-ID: <537D1E8B.1010505@zytor.com>
Date:	Wed, 21 May 2014 14:45:47 -0700
From:	"H. Peter Anvin" <hpa@...or.com>
To:	Borislav Petkov <bp@...en8.de>,
	Linus Torvalds <torvalds@...ux-foundation.org>
CC:	Jiri Kosina <jkosina@...e.cz>,
	Andy Lutomirski <luto@...capital.net>,
	Thomas Gleixner <tglx@...utronix.de>,
	Steven Rostedt <rostedt@...dmis.org>,
	Andi Kleen <andi@...stfloor.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Ingo Molnar <mingo@...nel.org>,
	"Luck, Tony" <tony.luck@...el.com>
Subject: Re: [RFC] x86_64: A real proposal for iret-less return to kernel

Adding Tony.

On 05/21/2014 02:43 PM, Borislav Petkov wrote:
> On Thu, May 22, 2014 at 06:37:26AM +0900, Linus Torvalds wrote:
>> Seriously. If an NMI is interrupted by an MCE, you might as well
>> consider the machine dead. Don't worry about it. We may or may not
>> recover, but it is *not* our problem.
> 
> I certainly like this way of handling it. We can even issue a nice
> banner saying something like "You're f*cked - go change hw."
> 

Actually, it would be a lot better to panic than deadlock (HA systems
tend to have something in place to catch the panic and/or reboot).  Any
way we can see if the CPU is already holding that lock and panic in that
case?

	-hpa


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