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

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Message-ID: <20061101121753.GA2205@elf.ucw.cz>
Date:	Wed, 1 Nov 2006 13:17:53 +0100
From:	Pavel Machek <pavel@....cz>
To:	Chris Wright <chrisw@...s-sol.org>
Cc:	akpm@...l.org, ak@....de, Rusty Russell <rusty@...tcorp.com.au>,
	Jeremy Fitzhardinge <jeremy@...p.org>,
	Zachary Amsden <zach@...are.com>, linux-kernel@...r.kernel.org,
	virtualization@...ts.osdl.org
Subject: Re: [PATCH 4/7] Allow selected bug checks to be skipped by paravirt kernels

On Sat 2006-10-28 00:00:04, Chris Wright wrote:
> 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.

> --- linux-2.6-pv.orig/arch/i386/kernel/cpu/intel.c
> +++ linux-2.6-pv/arch/i386/kernel/cpu/intel.c
> @@ -107,7 +107,7 @@ static void __cpuinit init_intel(struct 
>  	 * Note that the workaround only should be initialized once...
>  	 */
>  	c->f00f_bug = 0;
> -	if ( c->x86 == 5 ) {
> +	if (!paravirt_enabled() && c->x86 == 5) {

I'd do x86==5 check first... pentiums are not common any more.

								Pavel
-- 
(english) http://www.livejournal.com/~pavelmachek
(cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html
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