From: Steven Rostedt <rostedt@goodmis.org>
To: Andy Lutomirski <luto@amacapital.net>
Cc: LKML <linux-kernel@vger.kernel.org>, Jiri Olsa <jolsa@redhat.com>
Subject: Question: Outer NMI can nest if from user mode?
Date: Thu, 18 Aug 2016 11:21:55 -0400 [thread overview]
Message-ID: <20160818112155.634bebcb@gandalf.local.home> (raw)
Hi Andy,
I was reading some of the comments in nmi.c and came across this:
/*
* NMIs can page fault or hit breakpoints which will cause it to lose
* its NMI context with the CPU when the breakpoint or page fault does an IRET.
*
* As a result, NMIs can nest if NMIs get unmasked due an IRET during
* NMI processing. On x86_64, the asm glue protects us from nested NMIs
* if the outer NMI came from kernel mode, but we can still nest if the
* outer NMI came from user mode.
What confuses me is "but we can still nest if the outer NMI came from
user mode".
How can that happen? You mean do_nmi() can be called nested even on
x86_64 if the first NMI happened in user mode?
-- Steve
next reply other threads:[~2016-08-19 1:00 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-08-18 15:21 Steven Rostedt [this message]
2016-08-18 15:48 ` Steven Rostedt
2016-08-18 15:56 ` Steven Rostedt
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