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Re: [Xen-devel] [PATCH] Disable SMP on the MacBook by default

To: "Ian Pratt" <m+Ian.Pratt@xxxxxxxxxxxx>
Subject: Re: [Xen-devel] [PATCH] Disable SMP on the MacBook by default
From: Marco Gerards <mgerards@xxxxxxxxx>
Date: Thu, 14 Sep 2006 00:11:53 +0200
Cc: xen-devel@xxxxxxxxxxxxxxxxxxx, Marco Gerards <mgerards@xxxxxxxxx>
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"Ian Pratt" <m+Ian.Pratt@xxxxxxxxxxxx> writes:


>> The SMP issue can be avoided from GRUB when you press the "right
>> arrow" key instead of "enter" to boot.  Someone mentioned this on the
>> mailinglist, perhaps that is why you mixed up the two?
> This does kinda suggest that a further Grub patch might be part of the
> solution, no?

This is something I looked at, of course.  The GRUB code doesn't make
a difference between "right arrow" and return.  Besides that, it
doesn't work with the timeout either.

> Are there any issues with SMP linux 2.6.16 at all?

No, unless you disable ACPI.

The FreeBSD and NetBSD hackers have encountered the same problem.
They were not able to come up with a patch yet.

> Any idea what's going on?

The second core can not be initialized because the INIT IPI does not
arrive.  It only happens on the MacBook and not on the desktop Intel
Macs.  On the MacBook the second core is put into deep sleep mode.  It
should get out of sleep mode when an IPI or interrupt is received.

That does not happen.  It looks like the keyboard interrupt does
wakeup the second core, after which the IPI is received.

The annoying thing is that both the keyboard handling and ACPI on the
Intel Mac is a big mess.  There are a lot of bugs.  It could also be a
bug in the processor itself.  The reason why Windows and Linux work is
that the ACPI interpreter is used, perhaps this also has a side effect
of waking up the second core.

> What are distros link Ubuntu using for booting on MacBook? Do they go
> with bootcamp/grub, or elilo?

Sorry, I am not sure what you mean.  English is not my native
language.  Do you mean which bootloaders they use by default?

When I was installing Ubuntu for the first time on the MacBook, it
tried installing GRUB and failed.  First I tried lilo which worked.
Later I started using GRUB.  I haven't seen ELILO being used anywhere.


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