linux-kernel - Re: [RFC PATCH] x86 NMI-safe INT3 and Page Fault (v5)

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Date:	Mon, 21 Apr 2008 13:42:39 -0400
From:	Mathieu Desnoyers <compudj@...stal.dyndns.org>
To:	"H. Peter Anvin" <hpa@...or.com>
Cc:	Pavel Machek <pavel@....cz>, mingo@...e.hu, akpm@...l.org,
	Jeremy Fitzhardinge <jeremy@...p.org>,
	Steven Rostedt <rostedt@...dmis.org>,
	"Frank Ch. Eigler" <fche@...hat.com>, linux-kernel@...r.kernel.org
Subject: Re: [RFC PATCH] x86 NMI-safe INT3 and Page Fault (v5)

* H. Peter Anvin (hpa@...or.com) wrote:
> Pavel Machek wrote:
>>> There is also the page fault case. I think putting this test in
>>> ret_from_exception would be both safe (it is executed for any
>>> exception return) and fast (exceptions are rare).
>> Eh? I thought that page fault is one of the hottest paths in kernel
>> (along with syscall and packet receive/send)...
>> 								Pavel
>

On x86_64, we can pinpoint only the page faults returning to the kernel,
which are rare and only caused by vmalloc accesses. Ideally we could do
the same on x86_32.

> Yeah, and the concept of handling page faults inside an NMI handler is pure 
> fantasy.
>
> 	-hpa
>

-- 
Mathieu Desnoyers
Computer Engineering Ph.D. Student, Ecole Polytechnique de Montreal
OpenPGP key fingerprint: 8CD5 52C3 8E3C 4140 715F  BA06 3F25 A8FE 3BAE 9A68
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