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 14:57:27 +0200
From:   Peter Zijlstra <peterz@...radead.org>
To:     Wei Wang <wei.w.wang@...el.com>
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 Thu, Sep 20, 2018 at 08:58:16PM +0800, Wei Wang wrote:
> 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?

Sure.