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RE: [Xen-devel] SMP on the MacBook

To: "Marco Gerards" <mgerards@xxxxxxxxx>, <xen-devel@xxxxxxxxxxxxxxxxxxx>
Subject: RE: [Xen-devel] SMP on the MacBook
From: "Ian Pratt" <m+Ian.Pratt@xxxxxxxxxxxx>
Date: Wed, 9 Aug 2006 21:05:43 +0100
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Thread-topic: [Xen-devel] SMP on the MacBook
> Xen (testing) works perfectly for me when starting it with "nosmp",
> however when not using it, it crashes while starting up the second
> core.  There have been some bug report on this issue already.

Have you tried -unstable? Some potentially relevant files have been

Also, exactly which version of Linux boots OK? Does 2.6.16 e.g. from the


> Below I will explain the problem in more detail and with some
> observations.  I will be very grateful if someone can come up with
> ideas of how to fix this or give me some ideas that can lead to a
> solution.  Not only Xen has this problem, but so has FreeBSD and
> NetBSD, so a solution will be beneficial to these projects as well.
> What happens is the following: The first core sends two IPI
> messages(INIT and STARTUP) to start the second core.  When the second
> core is started, it notifies the first core of this so it can continue
> with the boot process.  However, the second core is not started by
> these messages, the loop that waits for the second core times out,
> continues and Xen crashes.
> One strange thing is that Xen initializes the second core properly
> when you press a key on the keyboard after the IPIs are sent.  I am
> expecting this interrupt somehow wakes up the second core so it can
> accept and process the IPIs.  Because it is a laptop the second core
> is put in deep sleep mode to save power in case an OS does not use
> this core at all.  But as I understand it, it should wake up when an
> INIT IPI arrives.
> The problems I am having with Xen can be reproduced with linux when
> booting with "acpi=ht", which means the ACPI interpreter is not
> started.
> Hopefully someone has some ideas how to deal with this issue and how
> to properly fix this.  If you want more information or want me to test
> things, feel free to ask.
> Thanks,
> Marco
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