linux-kernel - Re: [PATCH 2/6] lguest tsc fix

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Date:	Wed, 06 Jun 2007 10:25:49 +1000
From:	Rusty Russell <rusty@...tcorp.com.au>
To:	Andi Kleen <ak@....de>
Cc:	Andrew Morton <akpm@...ux-foundation.org>,
	lkml - Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 2/6] lguest tsc fix

On Tue, 2007-06-05 at 20:15 +0200, Andi Kleen wrote:
> On Wed, Jun 06, 2007 at 12:56:36AM +1000, Rusty Russell wrote:
> > In recent -mm kernels, the TSC capability cannot be disabled,
> > resulting in a divide by zero error in the normal sched_clock.
> 
> That will hopefully change. I hope hpa will just undo this.
> 
> > 
> > The correct fix is to have a special lguest sched_clock
> > implementation: this is as simple as it gets.
> 
> But gettimeofday might still use it. Is that ok for you?

Yes, I don't think it will be any worse than before.  Basically the
guest uses a dumb jiffies-based clock.  The TSC patch later in this same
series changes it back to use the native sched_clock, and overrides
tsc_khz instead (based on information from the host).

Thanks,
Rusty.


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