linux-kernel - Re: [Xen-devel] [PATCH] ARM: xen: only set pm function ptrs for Xen guests

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Date:	Wed, 28 Aug 2013 17:32:53 +0100
From:	Julien Grall <julien.grall@...aro.org>
To:	Rob Herring <robherring2@...il.com>
CC:	xen-devel@...ts.xensource.com,
	linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
	Rob Herring <rob.herring@...xeda.com>,
	Stefano Stabellini <stefano.stabellini@...citrix.com>
Subject: Re: [Xen-devel] [PATCH] ARM: xen: only set pm function ptrs for Xen
 guests

On 08/28/2013 05:19 PM, Rob Herring wrote:
> From: Rob Herring <rob.herring@...xeda.com>
> 
> xen_pm_init was unconditionally setting pm_power_off and arm_pm_restart
> function pointers. This breaks multi-platform kernels. Move this
> initialization into xen_guest_init, so it is conditional on running as a
> Xen guest.
> 
> Cc: Stefano Stabellini <stefano.stabellini@...citrix.com>
> Signed-off-by: Rob Herring <rob.herring@...xeda.com>
> ---
> This breaks reset and poweroff for Midway when Xen is enabled. This 
> should go into 3.11 or stable.
> Rob
> 
>  arch/arm/xen/enlighten.c | 12 +++---------
>  1 file changed, 3 insertions(+), 9 deletions(-)
> 
> diff --git a/arch/arm/xen/enlighten.c b/arch/arm/xen/enlighten.c
> index 8a6295c..fa86452 100644
> --- a/arch/arm/xen/enlighten.c
> +++ b/arch/arm/xen/enlighten.c
> @@ -263,6 +263,9 @@ static int __init xen_guest_init(void)
>  	if (xen_vcpu_info == NULL)
>  		return -ENOMEM;
>  
> +	pm_power_off = xen_power_off;
> +	arm_pm_restart = xen_restart;
> +

I think it's too early to set pm callbacks. If Linux is running as dom0,
xen needs to overwrite the power management callback. Otherwise, dom0
could shutdown/restart the whole platform, that is annoying.
For instance, on the versatile express, the power management callback
are set very late (ie during driver initialization).

pm callbacks should be updated by a late initcall and check if xen is
enabled.

>  	gnttab_init();
>  	if (!xen_initial_domain())
>  		xenbus_probe(NULL);
> @@ -271,15 +274,6 @@ static int __init xen_guest_init(void)
>  }
>  core_initcall(xen_guest_init);
>  
> -static int __init xen_pm_init(void)
> -{
> -	pm_power_off = xen_power_off;
> -	arm_pm_restart = xen_restart;
> -
> -	return 0;
> -}
> -subsys_initcall(xen_pm_init);
> -
>  static irqreturn_t xen_arm_callback(int irq, void *arg)
>  {
>  	xen_hvm_evtchn_do_upcall();
> 


-- 
Julien Grall
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