From: Michal Schulz <michal.schulz@gmx.de>
To: qemu-devel@nongnu.org
Subject: Re: [Qemu-devel] Re: [PATCH] Reboot CPU on triple fault
Date: Wed, 16 Apr 2008 12:17:32 +0200 [thread overview]
Message-ID: <200804161217.33019.michal.schulz@gmx.de> (raw)
In-Reply-To: <4805CC9B.7050809@suse.de>
On Wednesday 16 April 2008, Kevin Wolf wrote:
> > For old MS-DOS apps / OSes, I have the impression this can happen
> > hundreds of times per second. It's part of task context switching and
> > BIOS calls.
>
> I have to admit that I'm all but an 286 PM expert. What exactly is a
> triple fault doing there? If it leads to a reset as implemented here, I
> can hardly imagine that it is of much use in regular context switching.
It is required due to the "feature" of 286 CPU. Once 286 enters protected
mode, it cannot be switched back to the real mode. The only way to perform it
is resetting the CPU. A software which tries to go back from protected to
real mode sets the warm-reset vector in BIOS memory area, sets the reboot
reason variable in CMOS memory and issues a CPU reset.
CPU may be resetted due to a triple fault :)
--
Michal Schulz
next prev parent reply other threads:[~2008-04-16 10:18 UTC|newest]
Thread overview: 40+ messages / expand[flat|nested] mbox.gz Atom feed top
2008-03-29 18:13 [Qemu-devel] [PATCH] Reboot CPU on triple fault Hervé Poussineau
2008-03-30 1:36 ` Alexander Graf
2008-03-31 9:52 ` Kevin Wolf
2008-04-15 16:05 ` [Qemu-devel] " Jan Kiszka
2008-04-15 16:57 ` Paul Brook
2008-04-16 8:37 ` Kevin Wolf
2008-04-16 9:23 ` Jamie Lokier
2008-04-16 9:51 ` Antoine Kaufmann
2008-04-16 9:53 ` Kevin Wolf
2008-04-16 10:17 ` Michal Schulz [this message]
2008-04-16 10:25 ` Michal Schulz
2008-04-16 12:08 ` Kevin Wolf
2008-04-16 10:22 ` Jan Kiszka
2008-04-16 11:34 ` Jamie Lokier
2008-04-16 14:44 ` Anthony Liguori
2008-04-16 8:18 ` Kevin Wolf
2008-04-16 12:02 ` Jan Kiszka
2008-04-16 12:09 ` Avi Kivity
2008-04-16 12:36 ` Kevin Wolf
2008-04-16 12:57 ` Jamie Lokier
2008-04-16 12:44 ` [Qemu-devel] [PATCH] x86: Reboot CPU on triple fault - Version 3 Jan Kiszka
2008-04-16 13:35 ` [Qemu-devel] [PATCH] x86: Reboot CPU on triple fault - Version 4 Kevin Wolf
2008-04-16 14:18 ` [Qemu-devel] " Jan Kiszka
2008-04-16 14:33 ` [Qemu-devel] [PATCH] x86: Reboot CPU on triple fault - Version 5 Kevin Wolf
2008-04-16 14:57 ` [Qemu-devel] [PATCH] x86: Reboot CPU on triple fault - Version 6 Kevin Wolf
2008-04-17 9:52 ` [Qemu-devel] " Jan Kiszka
2008-04-18 14:06 ` [Qemu-devel] " Anthony Liguori
2008-04-21 11:53 ` Kevin Wolf
2008-05-26 14:46 ` [Qemu-devel] " Jan Kiszka
2008-05-27 16:01 ` [Qemu-devel] [PATCH] x86: Reboot CPU on triple fault - Version 8 Jan Kiszka
2008-05-27 16:17 ` [Qemu-devel] " Jan Kiszka
2008-04-16 14:37 ` [Qemu-devel] Re: [PATCH] x86: Reboot CPU on triple fault - Version 4 Anthony Liguori
2008-04-17 8:07 ` Jan Kiszka
2008-04-17 12:49 ` Anthony Liguori
2008-04-17 14:10 ` Jan Kiszka
2008-04-17 18:30 ` Anthony Liguori
2008-04-17 19:24 ` Jan Kiszka
2008-04-18 8:38 ` Kevin Wolf
2008-04-18 14:08 ` Anthony Liguori
2008-04-21 9:37 ` Kevin Wolf
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