linux-kernel - Re: lguest rebroken in 2.6.22-rc3-mm1

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Date:	Mon, 4 Jun 2007 20:12:15 +0200
From:	Andi Kleen <ak@...e.de>
To:	Andrew Morton <akpm@...ux-foundation.org>
Cc:	Matt Mackall <mpm@...enic.com>,
	Rusty Russell <rusty@...tcorp.com.au>,
	linux-kernel@...r.kernel.org
Subject: Re: lguest rebroken in 2.6.22-rc3-mm1

> >
> > Looks like this one got lost in rc3-mm1.
>
> Andi said that he fixed the zero-divide by other means?

I determined it cannot happen in my source tree. When notsc
is passed TSC CPUID is cleared and sched-clock works.

I suspect what happens is that lguest forgets to clear the TSC cpuid
bit when it disables TSC. Then the TSC frequency doesn't get computed
and sched-clock can divide by zero.That's purely a lguest bug that needs
to be fixed in lguest with a 
clear_bit(X86_FEATURE_TSC, &boot_cpu_data.x86_capability) 
somewhere

-Andi

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