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Date: Wed, 06 Jun 2012 09:00:17 +0800
From: "Yan, Zheng" <zheng.z.yan@intel.com>
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To: Peter Zijlstra <peterz@infradead.org>
CC: Stephane Eranian <eranian@google.com>, linux-kernel@vger.kernel.org
Subject: Re: [PATCH] perf, x86: Fix Intel shared extra MSR allocation
References: <1338520856-21020-1-git-send-email-zheng.z.yan@intel.com>  <CABPqkBScjC5fJbTc1rYtbtRqOCyJ+7QUbdE32DgMcffBAGJNVw@mail.gmail.com>  <CAAM7YAkYgUjwQptYvyeVawzcD5x4c-bTT_=+6AMyUb+-6HoMuQ@mail.gmail.com>  <1338891271.28282.155.camel@twins>  <CABPqkBSv8CbMzUiRsN2uOF1v6rFTpzhQqNbo7OKe-nzsus0GDg@mail.gmail.com>  <1338892071.28282.157.camel@twins>  <CABPqkBSqLpa4X-WbR0PkouYvhODT78r3pxWq70=PTj1j=a307Q@mail.gmail.com>  <1338898024.28282.160.camel@twins> <1338899999.28282.164.camel@twins>  <CABPqkBRCMAnPH3UW0=afMw4-YXgwQ5D-NLMEtnNWde_Tzh3aew@mail.gmail.com>  <1338901490.28282.167.camel@twins> <1338903031.28282.175.camel@twins> <1338904586.28282.183.camel@twins>
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On 06/05/2012 09:56 PM, Peter Zijlstra wrote:
>> @@ -1157,14 +1163,14 @@ __intel_shared_reg_get_constraints(struct cpu_hw_events *cpuc,
>> >  	struct event_constraint *c = &emptyconstraint;
>> >  	struct er_account *era;
>> >  	unsigned long flags;
>> > -	int orig_idx = reg->idx;
>> > +	int idx = reg->idx;
>> >  
>> >  	/* already allocated shared msr */
>> >  	if (reg->alloc)
>> >  		return NULL; /* call x86_get_event_constraint() */
> I'm afraid that needs to be:
> 
> 	/*
> 	 * reg->alloc can be set due to existing state, so for fake cpuc
> 	 * we need to ignore this, otherwise we might fail to allocate
> 	 * proper fake state for this extra reg constraint. Also see
> 	 * the comment below.
> 	 */
> 	if (reg->alloc && !cpuc->is_fake)
> 		return NULL; /* call x86_get_event_constraints() */
> 
Agree

Regards
Yan, Zheng