From: Steven Rostedt <rostedt@goodmis.org>
To: "H. Peter Anvin" <hpa@zytor.com>
Cc: linux-kernel@vger.kernel.org, Ingo Molnar <mingo@elte.hu>,
Andrew Morton <akpm@linux-foundation.org>,
Thomas Gleixner <tglx@linutronix.de>,
Peter Zijlstra <peterz@infradead.org>,
Frederic Weisbecker <fweisbec@gmail.com>,
Linus Torvalds <torvalds@linux-foundation.org>,
Mathieu Desnoyers <mathieu.desnoyers@efficios.com>,
Andi Kleen <andi@firstfloor.org>,
"H. Peter Anvin" <hpa@linux.intel.com>,
Paul Turner <pjt@google.com>
Subject: Re: [RFC][PATCH 5/5 v2] x86: Allow NMIs to hit breakpoints in i386
Date: Wed, 14 Dec 2011 14:33:15 -0500 [thread overview]
Message-ID: <1323891195.23971.60.camel@gandalf.stny.rr.com> (raw)
In-Reply-To: <4EE8EA61.9050902@zytor.com>
On Wed, 2011-12-14 at 10:26 -0800, H. Peter Anvin wrote:
> On 12/13/2011 06:52 PM, Steven Rostedt wrote:
> > With i386, NMIs and breakpoints use the current stack and they
> > do not reset the stack pointer to a fix point that might corrupt
> > a previous NMI or breakpoint (as it does in x86_64). But NMIs are
> > still not made to be re-entrant, and need to prevent the case that
> > an NMI hitting a breakpoint (which does an iret), doesn't allow
> > another NMI to run.
>
> Okay... what about the other way around: avoiding the IRET when invoked
> from an NMI context and therefore leaving NMI disabled until the
> appropriate time?
Linus was against this approach. He didn't want the ugliness of NMI to
spread to other code, by adding ugly handlers around the 'iret' of
breakpoints and exceptions.
-- Steve
prev parent reply other threads:[~2011-12-14 19:33 UTC|newest]
Thread overview: 15+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-12-14 2:52 [RFC][PATCH 0/5 v2] x86: Find a way to allow breakpoints in NMIs Steven Rostedt
2011-12-14 2:52 ` [RFC][PATCH 1/5 v2] x86: Do not schedule while still in NMI context Steven Rostedt
2011-12-14 2:52 ` [RFC][PATCH 2/5 v2] x86: Document the NMI handler about not using paranoid_exit Steven Rostedt
2011-12-14 2:52 ` [RFC][PATCH 3/5 v2] x86: Add workaround to NMI iret woes Steven Rostedt
2011-12-14 2:52 ` [RFC][PATCH 4/5 v2] x86: Keep current stack in NMI breakpoints Steven Rostedt
2011-12-14 13:43 ` Mathieu Desnoyers
2011-12-14 16:19 ` Steven Rostedt
2011-12-15 19:15 ` Steven Rostedt
2012-01-08 8:59 ` [tip:perf/core] x86: Add counter when debug stack is used with interrupts enabled tip-bot for Steven Rostedt
2011-12-14 2:52 ` [RFC][PATCH 5/5 v2] x86: Allow NMIs to hit breakpoints in i386 Steven Rostedt
2011-12-14 13:30 ` Mathieu Desnoyers
2011-12-14 13:40 ` Steven Rostedt
2011-12-14 13:44 ` Mathieu Desnoyers
2011-12-14 18:26 ` H. Peter Anvin
2011-12-14 19:33 ` Steven Rostedt [this message]
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