linux-kernel - Re: [PATCH 4/7] Allow selected bug checks to be skipped by paravirt kernels

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Message-ID: <20061102102059.GB1990@elf.ucw.cz>
Date:	Thu, 2 Nov 2006 11:20:59 +0100
From:	Pavel Machek <pavel@....cz>
To:	Zachary Amsden <zach@...are.com>
Cc:	Chris Wright <chrisw@...s-sol.org>, akpm@...l.org, ak@....de,
	Rusty Russell <rusty@...tcorp.com.au>,
	Jeremy Fitzhardinge <jeremy@...p.org>,
	linux-kernel@...r.kernel.org, virtualization@...ts.osdl.org
Subject: Re: [PATCH 4/7] Allow selected bug checks to be skipped by paravirt kernels

Hi!

> >>Allow selected bug checks to be skipped by paravirt kernels.  The two most
> >>important are the F00F workaround (which is either done by the hypervisor,
> >>or not required), and the 'hlt' instruction check, which can break under
> >>some hypervisors.
> >>    
> >
> >How can hlt check break? It is hlt;hlt;hlt, IIRC, that looks fairly
> >innocent to me.
> >  
> 
> Not if you use tickless timers that don't generate interrupts to unhalt 
> you, or if you delay ticks until the next scheduled timeout and you 
> haven't yet scheduled any timeout.  Both are likely in a hypervisor.

Well.. but you are working around problem, instead of fixing it.

Tickless kernels are possible on normal machines, too.

Please fix it properly... probably by requesting timer 10msec in
advance or something.
									Pavel
-- 
(english) http://www.livejournal.com/~pavelmachek
(cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html
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