Re: [PATCH v2 1/2] paravirt/locks: use new static key for controlling call of virt_spin_lock()

On 06/09/17 18:13, Waiman Long wrote:

On 09/06/2017 12:04 PM, Peter Zijlstra wrote:

quoted

On Wed, Sep 06, 2017 at 11:49:49AM -0400, Waiman Long wrote:

quoted

quoted

 #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