From mboxrd@z Thu Jan  1 00:00:00 1970
From: Keir Fraser <keir.xen@gmail.com>
Subject: Re: [PATCH] x86: default-disable MWAIT-based idle
 driver for CPUs without ARAT
Date: Wed, 26 Sep 2012 15:37:19 +0100
Message-ID: <CC88D1AF.40008%keir.xen@gmail.com>
References: <506326B7020000780009E013@nat28.tlf.novell.com>
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To: Jan Beulich <JBeulich@suse.com>, xen-devel <xen-devel@lists.xen.org>
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On 26/09/2012 15:00, "Jan Beulich" <JBeulich@suse.com> wrote:

> Without ARAT, and apparently only when using HPET broadcast mode as
> replacement, CPUs occasionally fail to wake up, causing the system to
> (transiently) hang. Until the reason is understood, disable the driver
> on such systems.
> 
> Signed-off-by: Jan Beulich <jbeulich@suse.com>

Acked-by: Keir Fraser <keir@xen.org>

> --- a/xen/arch/x86/cpu/mwait-idle.c
> +++ b/xen/arch/x86/cpu/mwait-idle.c
> @@ -71,7 +71,7 @@
>  # define pr_debug(fmt...)
>  #endif
>  
> -static __initdata bool_t no_mwait_idle;
> +static __initdata s8 no_mwait_idle = -1;
>  invbool_param("mwait-idle", no_mwait_idle);
>  
>  static unsigned int mwait_substates;
> @@ -500,6 +500,13 @@ int __init mwait_idle_init(struct notifi
> if (pm_idle_save)
> return -ENODEV;
>  
> + /* XXX The no-ARAT case is supposedly being taken care of, but at
> +  * least some systems without ARAT hang for some reason, apparently
> +  * only when using HPET broadcast mode (PIT broadcast mode seems to
> +  * be fine). */
> + if (no_mwait_idle < 0 && boot_cpu_has(X86_FEATURE_ARAT))
> +  no_mwait_idle = 0;
> +
> err = mwait_idle_probe();
> if (!err) {
> if (!boot_cpu_has(X86_FEATURE_ARAT))
> 
> 
> 
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