From mboxrd@z Thu Jan  1 00:00:00 1970
From: Wei Wang <wei.w.wang@intel.com>
Subject: Re: [PATCH v2 1/8] perf/x86: add a function to get the lbr stack
Date: Fri, 07 Sep 2018 14:45:24 +0800
Message-ID: <5B921E84.4010008@intel.com>
References: <1536233456-12173-1-git-send-email-wei.w.wang@intel.com> <1536233456-12173-2-git-send-email-wei.w.wang@intel.com> <20180907032811.GO27886@tassilo.jf.intel.com>
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Cc: "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        "kvm@vger.kernel.org" <kvm@vger.kernel.org>,
        "pbonzini@redhat.com" <pbonzini@redhat.com>,
        "Liang, Kan" <kan.liang@intel.com>,
        "peterz@infradead.org" <peterz@infradead.org>,
        "mingo@redhat.com" <mingo@redhat.com>,
        "rkrcmar@redhat.com" <rkrcmar@redhat.com>,
        "Xu, Like" <like.xu@intel.com>
To: Andi Kleen <ak@linux.intel.com>
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In-Reply-To: <20180907032811.GO27886@tassilo.jf.intel.com>
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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