linux-kernel - Re: [PATCH v2 1/2] paravirt/locks: use new static key for controlling call of virt_spin

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Message-ID: <20170906160415.crt2ajuf6553bit7@hirez.programming.kicks-ass.net>
Date:   Wed, 6 Sep 2017 18:04:15 +0200
From:   Peter Zijlstra <peterz@...radead.org>
To:     Waiman Long <longman@...hat.com>
Cc:     Juergen Gross <jgross@...e.com>, linux-kernel@...r.kernel.org,
        xen-devel@...ts.xenproject.org, x86@...nel.org,
        virtualization@...ts.linux-foundation.org, jeremy@...p.org,
        chrisw@...s-sol.org, akataria@...are.com, rusty@...tcorp.com.au,
        boris.ostrovsky@...cle.com, hpa@...or.com, tglx@...utronix.de,
        mingo@...hat.com
Subject: Re: [PATCH v2 1/2] paravirt/locks: use new static key for
 controlling call of virt_spin_lock()

On Wed, Sep 06, 2017 at 11:49:49AM -0400, Waiman Long wrote:
> >  #define virt_spin_lock virt_spin_lock
> >  static inline bool virt_spin_lock(struct qspinlock *lock)
> >  {
> > +	if (!static_branch_likely(&virt_spin_lock_key))
> > +		return false;
> >  	if (!static_cpu_has(X86_FEATURE_HYPERVISOR))
> >  		return false;
> >  

Now native has two NOPs instead of one. Can't we merge these two static
branches?