[Xen-devel] [PATCH RFC v5 5/8] pvqspinlock, x86: Enable unfair queue spinlock in a KVM guest

[Waiman Long <Waiman.Long@xxxxxx>]

This patch adds a KVM init function to activate the unfair queue
spinlock in a KVM guest when the PARAVIRT_UNFAIR_LOCKS kernel config
option is selected.

Signed-off-by: Waiman Long <Waiman.Long@xxxxxx>
---
 arch/x86/kernel/kvm.c |   17 +++++++++++++++++
 1 files changed, 17 insertions(+), 0 deletions(-)

diff --git a/arch/x86/kernel/kvm.c b/arch/x86/kernel/kvm.c
index 713f1b3..a489140 100644
--- a/arch/x86/kernel/kvm.c
+++ b/arch/x86/kernel/kvm.c
@@ -826,3 +826,20 @@ static __init int kvm_spinlock_init_jump(void)
 early_initcall(kvm_spinlock_init_jump);
 
 #endif /* CONFIG_PARAVIRT_SPINLOCKS */
+
+#ifdef CONFIG_PARAVIRT_UNFAIR_LOCKS
+/*
+ * Enable unfair lock if running in a real para-virtualized environment
+ */
+static __init int kvm_unfair_locks_init_jump(void)
+{
+       if (!kvm_para_available())
+               return 0;
+
+       static_key_slow_inc(&paravirt_unfairlocks_enabled);
+       printk(KERN_INFO "KVM setup unfair spinlock\n");
+
+       return 0;
+}
+early_initcall(kvm_unfair_locks_init_jump);
+#endif
-- 
1.7.1


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