linux-kernel - Re: [PATCH v3 5/5] KVM/x86/lbr: lazy save the guest lbr stack

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Date:   Thu, 20 Sep 2018 20:58:16 +0800
From:   Wei Wang <wei.w.wang@...el.com>
To:     Peter Zijlstra <peterz@...radead.org>
CC:     linux-kernel@...r.kernel.org, kvm@...r.kernel.org,
        pbonzini@...hat.com, ak@...ux.intel.com, kan.liang@...el.com,
        mingo@...hat.com, rkrcmar@...hat.com, like.xu@...el.com,
        jannh@...gle.com, arei.gonglei@...wei.com
Subject: Re: [PATCH v3 5/5] KVM/x86/lbr: lazy save the guest lbr stack

On 09/20/2018 08:37 PM, Peter Zijlstra wrote:
> On Thu, Sep 20, 2018 at 06:05:59PM +0800, Wei Wang wrote:
>>   /**
>> + * lbr_select_user_callstack - check if the user callstack mode is set
>> + *
>> + * @lbr_select: the lbr select msr
>> + *
>> + * Returns: true if the msr is configured to the user callstack mode.
>> + * Otherwise, false.
>> + *
>> + */
>> +bool lbr_select_user_callstack(u64 lbr_select)
>> +{
>> +	return !!(lbr_select & LBR_USER_CALLSTACK);
>> +}
>> +EXPORT_SYMBOL_GPL(lbr_select_user_callstack);
> That function is pure and tiny, wth is that an exported symbol and not
> an inline?
Thanks Peter for the comments.

Because this function uses the LBR_ macros which are defined in this 
lbr.c file.
Do you think it would be OK to move all the above LBR_ macros to 
asm/perf_event.h?

Best,
Wei