Re: [PATCH v2 1/8] perf/x86: add a function to get the lbr stack

[Wei Wang]

On 09/07/2018 11:28 AM, Andi Kleen wrote:
> > +int perf_get_lbr_stack(struct perf_lbr_stack *stack)
> > +{
> > +	stack->lbr_nr = x86_pmu.lbr_nr;
> > +	stack->lbr_tos = x86_pmu.lbr_tos;
> > +	stack->lbr_from = x86_pmu.lbr_from;
> > +	stack->lbr_to = x86_pmu.lbr_to;
> > +
> > +	if (x86_pmu.intel_cap.lbr_format == LBR_FORMAT_INFO)
> > +		stack->lbr_info = MSR_LBR_INFO_0;
> > +	else
> > +		stack->lbr_info = 0;
> Seems weird to export the enum value if the enum isn't exported.
> How can it be used?

I'm not sure about the issue. The caller gets the value of 
MSR_LBR_INFO_0 (not the enum, LBR_FORMAT_INFO) only when the hardware 
supports it. If hardware doesn't support it, just sets it to 0, and 
there will be no lbr info msr to be passed through.

Best,
Wei