linux-kernel - Re: [Xen-devel] [PATCH] xen/arm: disable cpuidle when linux is running as dom0

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Message-ID: <alpine.DEB.2.02.1307171426300.8258@kaball.uk.xensource.com>
Date:	Wed, 17 Jul 2013 14:28:43 +0100
From:	Stefano Stabellini <stefano.stabellini@...citrix.com>
To:	Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>
CC:	Julien Grall <julien.grall@...aro.org>,
	<stefano.stabellini@...citrix.com>, <ian.campbell@...rix.com>,
	<patches@...aro.org>, <linux-kernel@...r.kernel.org>,
	<xen-devel@...ts.xen.org>, <linux-arm-kernel@...ts.infradead.org>
Subject: Re: [Xen-devel] [PATCH] xen/arm: disable cpuidle when linux is
 running as dom0

On Mon, 15 Jul 2013, Konrad Rzeszutek Wilk wrote:
> On Mon, Jul 15, 2013 at 03:21:41PM +0100, Julien Grall wrote:
> > When linux is running as dom0, Xen doesn't show the physical cpu but a
> > virtual CPU.
> > On some ARM SOC (for instance the exynos 5250), linux registers callbacks
> > for cpuidle. When these callbacks are called, they will modify
> > directly the physical cpu not the virtual one.
> It can impact the whole board
> > instead of dom0.

Certainly this is something that should be fixed at the hypervisor level
too. However I agree that Linux should try to avoid doing that when
running on Xen.



> Should you also call disable_cpufreq() ?

Sounds like a good idea.
Julien, could you add that to this patch?


> > 
> > Signed-off-by: Julien Grall <julien.grall@...aro.org>
> > ---
> >  arch/arm/xen/enlighten.c |    7 +++++++
> >  1 file changed, 7 insertions(+)
> > 
> > diff --git a/arch/arm/xen/enlighten.c b/arch/arm/xen/enlighten.c
> > index 49839d8..a98999f 100644
> > --- a/arch/arm/xen/enlighten.c
> > +++ b/arch/arm/xen/enlighten.c
> > @@ -24,6 +24,8 @@
> >  #include <linux/of.h>
> >  #include <linux/of_irq.h>
> >  #include <linux/of_address.h>
> > +#include <linux/cpuidle.h>
> > +#include <linux/cpufreq.h>
> >  
> >  #include <linux/mm.h>
> >  
> > @@ -292,6 +294,11 @@ static int __init xen_pm_init(void)
> >  {
> >  	pm_power_off = xen_power_off;
> >  	arm_pm_restart = xen_restart;
> > +	/*
> > +	 * Making sure board specific code will not set up ops for
> > +	 * cpu idle.
> > +	 */
> > +	disable_cpuidle();
> >  
> >  	return 0;
> >  }
> > -- 
> > 1.7.10.4
> > 
> > 
> > _______________________________________________
> > Xen-devel mailing list
> > Xen-devel@...ts.xen.org
> > http://lists.xen.org/xen-devel
> 
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