From: Avi Kivity <avi@redhat.com>
To: Steven Rostedt <rostedt@goodmis.org>
Cc: linux-kernel <linux-kernel@vger.kernel.org>,
Ingo Molnar <mingo@elte.hu>,
Linus Torvalds <torvalds@linux-foundation.org>,
"H. Peter Anvin" <hpa@zytor.com>,
Thomas Gleixner <tglx@linutronix.de>,
Paul Turner <pjt@google.com>,
Peter Zijlstra <peterz@infradead.org>,
Frederic Weisbecker <fweisbec@gmail.com>,
Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Subject: NMI vs #PF clash
Date: Tue, 22 May 2012 15:53:20 +0300 [thread overview]
Message-ID: <4FBB8C40.6080304@redhat.com> (raw)
The recent changes to NMI allow exceptions to take place in NMI
handlers, but I think that a #PF (say, due to access to vmalloc space)
is still problematic. Consider the sequence
#PF (cr2 set by processor)
NMI
...
#PF (cr2 clobbered)
do_page_fault()
IRET
...
IRET
do_page_fault()
address = read_cr2()
The last line reads the overwritten cr2 value.
I vaguely remember some discussion about this back in the day, but I
can't find anything in the code to save/restore cr2 in the NMI handler.
Did I miss it? Or perhaps the page fault handler ignores the incorrect
cr2 and IRETs, to fault back immediately?
--
error compiling committee.c: too many arguments to function
next reply other threads:[~2012-05-22 12:53 UTC|newest]
Thread overview: 18+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-05-22 12:53 Avi Kivity [this message]
2012-05-22 13:30 ` NMI vs #PF clash Steven Rostedt
2012-05-22 13:45 ` Avi Kivity
2012-05-22 14:09 ` Steven Rostedt
2012-05-22 14:20 ` Avi Kivity
2012-05-22 14:27 ` Steven Rostedt
2012-05-22 14:37 ` Avi Kivity
2012-05-22 14:50 ` Steven Rostedt
2012-05-22 15:22 ` Mathieu Desnoyers
2012-05-22 15:33 ` Linus Torvalds
2012-05-22 15:45 ` Avi Kivity
2012-05-22 15:47 ` H. Peter Anvin
2012-05-23 0:39 ` Steven Rostedt
2012-05-23 1:26 ` Brian Gerst
2012-05-23 8:32 ` Steven Rostedt
2012-05-23 8:56 ` Steven Rostedt
2012-06-11 4:22 ` [tip:x86/debug] x86: Save cr2 in NMI in case NMIs take a page fault tip-bot for Steven Rostedt
2012-06-11 4:24 ` [tip:x86/debug] x86: Save cr2 in NMI in case NMIs take a page fault (for i386) tip-bot for Steven Rostedt
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