linux-kernel - Re: apic: native_apic_write

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Date:	Sun, 14 Jun 2009 23:50:16 +0200
From:	Simon Holm Thøgersen <odie@...aau.dk>
To:	Cyrill Gorcunov <gorcunov@...il.com>
Cc:	linux-kernel <linux-kernel@...r.kernel.org>,
	Ingo Molnar <mingo@...e.hu>, Andi Kleen <andi@...stfloor.org>
Subject: Re: apic: native_apic_write_dummy warning

man, 15 06 2009 kl. 00:06 +0400, skrev Cyrill Gorcunov:
> [Cyrill Gorcunov - Sun, Jun 14, 2009 at 11:40:17PM +0400]
> ... 
> | Neither thermal interrupts nor mce will be functional if apic
> | is not properly set up (even having kernel compiled that way
> | it support both). So you may try to pass "lapic" boot option
> | and check if we're lucky in attempt to enable apic via force
> | push. Anyway this warn show that the code is to be fixed
> | (and native_apic_write_dummy done its work great catching
> |  useless apic->write operation). I'll handle it but a bit later.
> | 
> | Andi CC'ed since he is involved in MCE handling just for the
> | record.
> | 
> | 	-- Cyrill
> 
> Simon here is a patch I would appreciate if you test.

That was quick work :) No warning with the patch (or lapic).

> ---
> [PATCH -tip] x86: mce intel -- don't touch THERMAL_APIC_VECTOR if no active APIC
> 
> If APIC was disabled for some reason and not even mapped
> we should not try to enable thermal interrupts at all.
> 
> Reported-by: Simon Holm Thøgersen <odie@...aau.dk>

Tested-by: Simon Holm Thøgersen <odie@...aau.dk>

> Signed-off-by: Cyrill Gorcunov <gorcunov@...nvz.org>
> ---
>  arch/x86/kernel/cpu/mcheck/mce_intel.c |   10 ++++++++--
>  1 file changed, 8 insertions(+), 2 deletions(-)
> 
> Index: linux-2.6.git/arch/x86/kernel/cpu/mcheck/mce_intel.c
> =====================================================================
> --- linux-2.6.git.orig/arch/x86/kernel/cpu/mcheck/mce_intel.c
> +++ linux-2.6.git/arch/x86/kernel/cpu/mcheck/mce_intel.c
> @@ -21,9 +21,15 @@ void intel_init_thermal(struct cpuinfo_x
>  	int tm2 = 0;
>  	u32 l, h;
>  
> -	/* Thermal monitoring depends on ACPI and clock modulation*/
> -	if (!cpu_has(c, X86_FEATURE_ACPI) || !cpu_has(c, X86_FEATURE_ACC))
> +	/*
> +	 * Thermal monitoring depends on ACPI, clock modulation
> +	 * and APIC as well
> +	 */
> +	if (!cpu_has(c, X86_FEATURE_ACPI) || !cpu_has(c, X86_FEATURE_ACC) ||
> +		!cpu_has(c, X86_FEATURE_APIC)) {
> +		pr_debug("Thermal monitoring disabled\n");
>  		return;
> +	}
>  
>  	/*
>  	 * First check if its enabled already, in which case there might
> --
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