KVM: Enable pvspinlock after jump_label_init() to avoid VM hang

We use jump label to enable pv-spinlock. With the changes in (442e0973e927
Merge branch 'x86/jumplabel'), the jump label behaviour has changed
that would result in eventual hang of the VM since we would end up in a
situation where slow path locks would halt the vcpus but we will not be
able to wakeup the vcpu by lock releaser using unlock kick.

Similar problem in Xen and more detailed description is available in
a945928ea270 (xen: Do not enable spinlocks before jump_label_init()
has executed)

This patch splits kvm_spinlock_init to separate jump label changes with
pvops patching and also make jump label enabling after jump_label_init().

Signed-off-by: Raghavendra K T <raghavendra.kt@linux.vnet.ibm.com>
Reviewed-by: Paolo Bonzini <pbonzini@redhat.com>
Reviewed-by: Steven Rostedt <rostedt@goodmis.org>
Signed-off-by: Gleb Natapov <gleb@redhat.com>

1 files changed, 14 insertions, 3 deletions

diff --git a/arch/x86/kernel/kvm.c b/arch/x86/kernel/kvm.c
index 697b93af02d..a0e2a8a80c9 100644
--- a/arch/x86/kernel/kvm.c
+++ b/arch/x86/kernel/kvm.c
@@ -775,11 +775,22 @@ void __init kvm_spinlock_init(void)
 	if (!kvm_para_has_feature(KVM_FEATURE_PV_UNHALT))
 		return;
 
-	printk(KERN_INFO "KVM setup paravirtual spinlock\n");
+	pv_lock_ops.lock_spinning = PV_CALLEE_SAVE(kvm_lock_spinning);
+	pv_lock_ops.unlock_kick = kvm_unlock_kick;
+}
+
+static __init int kvm_spinlock_init_jump(void)
+{
+	if (!kvm_para_available())
+		return 0;
+	if (!kvm_para_has_feature(KVM_FEATURE_PV_UNHALT))
+		return 0;
 
 	static_key_slow_inc(&paravirt_ticketlocks_enabled);
+	printk(KERN_INFO "KVM setup paravirtual spinlock\n");
 
-	pv_lock_ops.lock_spinning = PV_CALLEE_SAVE(kvm_lock_spinning);
-	pv_lock_ops.unlock_kick = kvm_unlock_kick;
+	return 0;
 }
+early_initcall(kvm_spinlock_init_jump);
+
 #endif	/* CONFIG_PARAVIRT_SPINLOCKS */