From mboxrd@z Thu Jan  1 00:00:00 1970
From: Juergen Gross <jgross@suse.com>
Subject: Re: [PATCH v2 1/2] paravirt/locks: use new static key for controlling
	call of virt_spin_lock()
Date: Wed, 6 Sep 2017 19:33:10 +0200
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To: Waiman Long <longman@redhat.com>, Peter Zijlstra <peterz@infradead.org>
Cc: jeremy@goop.org, x86@kernel.org, linux-kernel@vger.kernel.org, virtualization@lists.linux-foundation.org, chrisw@sous-sol.org, mingo@redhat.com, tglx@linutronix.de, hpa@zytor.com, xen-devel@lists.xenproject.org, akataria@vmware.com, boris.ostrovsky@oracle.com
List-Id: virtualization@lists.linuxfoundation.org

On 06/09/17 18:13, Waiman Long wrote:
> On 09/06/2017 12:04 PM, Peter Zijlstra wrote:
>> 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?
> 
> 
> I guess we can remove the static_cpu_has() call. Just that any spin_lock
> calls before native_pv_lock_init() will use the virt_spin_lock(). That
> is still OK as the init call is done before SMP starts.

Hmm, right. I'll send V3 in some minutes.


Juergen