Commit 3dbef3e3 authored Oct 09, 2013 by Raghavendra K T Committed by Gleb Natapov Oct 15, 2013

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



We use jump label to enable pv-spinlock. With the changes in (442e0973
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
a945928e (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>

parent 9d05746e

arch/x86/kernel/kvm.c

+14 −3

Original line number	Diff line number	Diff line
		@@ -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 */

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