[PATCH] x86/paravirt: Disable virt spinlock when CONFIG_PARAVIRT_SPINLOCKS disabled

[Chen Yu]

Performance drop is reported when running encode/decode workload and
BenchSEE cache sub-workload.
Bisect points to commit ce0a1b608bfc ("x86/paravirt: Silence unused
native_pv_lock_init() function warning"). When CONFIG_PARAVIRT_SPINLOCKS
is disabled the virt_spin_lock_key is set to true on bare-metal.
The qspinlock degenerates to test-and-set spinlock, which decrease the
performance on bare-metal.

Fix this by disabling virt_spin_lock_key if CONFIG_PARAVIRT_SPINLOCKS
is not set, or it is on bare-metal.

Fixes: ce0a1b608bfc ("x86/paravirt: Silence unused native_pv_lock_init() function warning")
Suggested-by: Qiuxu Zhuo <qiuxu.zhuo@xxxxxxxxx>
Reported-by: Prem Nath Dey <prem.nath.dey@xxxxxxxxx>
Reported-by: Xiaoping Zhou <xiaoping.zhou@xxxxxxxxx>
Signed-off-by: Chen Yu <yu.c.chen@xxxxxxxxx>
---
 arch/x86/kernel/paravirt.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/x86/kernel/paravirt.c b/arch/x86/kernel/paravirt.c
index 5358d43886ad..ee51c0949ed8 100644
--- a/arch/x86/kernel/paravirt.c
+++ b/arch/x86/kernel/paravirt.c
@@ -55,7 +55,7 @@ DEFINE_STATIC_KEY_TRUE(virt_spin_lock_key);
 
 void __init native_pv_lock_init(void)
 {
-	if (IS_ENABLED(CONFIG_PARAVIRT_SPINLOCKS) &&
+	if (!IS_ENABLED(CONFIG_PARAVIRT_SPINLOCKS) ||
 	    !boot_cpu_has(X86_FEATURE_HYPERVISOR))
 		static_branch_disable(&virt_spin_lock_key);
 }
-- 
2.25.1