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From: Ingo Molnar <mingo@elte.hu>
To: Steven Rostedt <rostedt@goodmis.org>
Cc: linux-kernel@vger.kernel.org,
	Andrew Morton <akpm@linux-foundation.org>,
	"H. Peter Anvin" <hpa@zytor.com>,
	Peter Zijlstra <a.p.zijlstra@chello.nl>
Subject: Re: [PATCH][GIT PULL][v3.3] x86: Test saved %rip in NMI to determine nested NMI
Date: Mon, 20 Feb 2012 09:10:45 +0100	[thread overview]
Message-ID: <20120220081045.GD30810@elte.hu> (raw)
In-Reply-To: <1329663451.25686.21.camel@gandalf.stny.rr.com>


* Steven Rostedt <rostedt@goodmis.org> wrote:

> On Sun, 2012-02-19 at 13:56 +0100, Ingo Molnar wrote:
> > * Steven Rostedt <rostedt@goodmis.org> wrote:
> > 
> > > Ingo,
> > > 
> > > I found that it is possible for userspace to prevent an NMI 
> > > from triggering while it is running by setting its stack 
> > > pointer to that of the NMI stack. This tricks the NMI nested 
> > > algorithm in thinking that the NMI is nested. The easy 
> > > solution to this is to test the %rip to make sure that the NMI 
> > > happened in kernel mode before testing for nesting.
> > 
> > Ouch...
> 
> Note, it does not seem to cause any destruction, but screw up 
> profiling.

Except if the source of the NMI was not profiling, right?

Thanks,

	Ingo

  reply	other threads:[~2012-02-20  8:10 UTC|newest]

Thread overview: 19+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2012-02-19  2:06 [PATCH][GIT PULL][v3.3] x86: Test saved %rip in NMI to determine nested NMI Steven Rostedt
2012-02-19 12:56 ` Ingo Molnar
2012-02-19 13:46   ` hpanvin@gmail.com
2012-02-19 13:48     ` Ingo Molnar
2012-02-19 20:34     ` Steven Rostedt
2012-02-19 20:45       ` H. Peter Anvin
2012-02-19 21:00         ` Steven Rostedt
2012-02-19 14:57   ` Steven Rostedt
2012-02-20  8:10     ` Ingo Molnar [this message]
2012-02-20 14:41       ` Steven Rostedt
2012-02-20 15:34         ` Ingo Molnar
2012-02-20 17:07           ` H. Peter Anvin
2012-02-19 21:43   ` [PATCH v2][GIT PULL][v3.3] x86: Test saved %cs " Steven Rostedt
2012-02-20 11:47     ` [tip:x86/urgent] x86/nmi: Test saved %cs in NMI to determine nested NMI case tip-bot for Steven Rostedt
2012-02-20 16:51       ` Steven Rostedt
2012-02-27 21:29         ` Greg KH
2012-02-20 18:03       ` Linus Torvalds
2012-02-20 18:26         ` Steven Rostedt
2012-02-21 22:08         ` [tip:x86/urgent] x86: Specify a size for the cmp in the NMI handler tip-bot for Steven Rostedt

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