Re: [PATCH] perf, x86: Fix Intel shared extra MSR allocation

["Yan, Zheng" <zheng.z.yan@intel.com>]

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