linux-kernel - Re: [PATCH -tip] perf_counter/x86: Remove masking and unmasking of LVT error register.

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Date:	Thu, 28 May 2009 10:33:40 +0200
From:	Ingo Molnar <mingo@...e.hu>
To:	Yong Wang <yong.y.wang@...ux.intel.com>
Cc:	linux-kernel@...r.kernel.org
Subject: Re: [PATCH -tip] perf_counter/x86: Remove masking and unmasking of
	LVT error register.


* Yong Wang <yong.y.wang@...ux.intel.com> wrote:

> Masking and unmasking of LVT error register become unnecessary as 
> NMI mode will be used all the time.
> 
> Signed-off-by: Yong Wang <yong.y.wang@...el.com>
> 
> ---
>  perf_counter.c |    6 ------
>  1 file changed, 6 deletions(-)
> 
> diff --git a/arch/x86/kernel/cpu/perf_counter.c b/arch/x86/kernel/cpu/perf_counter.c
> index 2eeaa99..444bcf2 100644
> --- a/arch/x86/kernel/cpu/perf_counter.c
> +++ b/arch/x86/kernel/cpu/perf_counter.c
> @@ -865,22 +865,16 @@ void set_perf_counter_pending(void)
>  
>  void perf_counters_lapic_init(int nmi)
>  {
> -	u32 apic_val;
> -
>  	if (!x86_pmu_initialized())
>  		return;
>  
>  	/*
>  	 * Enable the performance counter vector in the APIC LVT:
>  	 */
> -	apic_val = apic_read(APIC_LVTERR);
> -
> -	apic_write(APIC_LVTERR, apic_val | APIC_LVT_MASKED);
>  	if (nmi)
>  		apic_write(APIC_LVTPC, APIC_DM_NMI);
>  	else
>  		apic_write(APIC_LVTPC, LOCAL_PERF_VECTOR);
> -	apic_write(APIC_LVTERR, apic_val);
>  }

i'd suggest to remove the 'nmi' parameter as well to this function. 
(and any other dynamic flags that deal with nmi/irq distinctions)

	Ingo
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