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Re: [Xen-devel] [PATCH v7 06/11] pvqspinlock, x86: Allow unfair queue spinlock in a KVM guest



On 03/20/2014 06:01 PM, Paolo Bonzini wrote:
Il 19/03/2014 21:14, Waiman Long ha scritto:
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


No! Please do what I asked you to do. You are not handling Hyper-V or VMWare. Just use X86_FEATURE_HYPERVISOR and it will cover all hypervisors that actually follow Intel's guidelines.

Paolo

OK, I can modify the patch to use X86_FEATURE_HYPERVISOR.

-Longman


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