KVM: ia64: fix locking order entering guest

Reorder locking as down_read() may return with local interrupts enabled,
which means we could go into vti_vcpu_run() with interrupts enabled.

This caused random crashes on the Altix as the timer interrupt tried
to read a memory mapped clock source, for which the TLB had not yet been
reinstated in the exit, before ipsr was retored.

Signed-off-by: Jes Sorensen <jes@sgi.com>
Acked-by: Xiantao Zhang <xiantao.zhang@intel.com>
Signed-off-by: Avi Kivity <avi@redhat.com>

arch/ia64/kvm/kvm-ia64.c

@@ -610,20 +610,22 @@ static int __vcpu_run(struct kvm_vcpu *vcpu, struct kvm_run *kvm_run)
 	int r;
 
 again:
-	preempt_disable();
-	local_irq_disable();
-
 	if (signal_pending(current)) {
-		local_irq_enable();
-		preempt_enable();
 		r = -EINTR;
 		kvm_run->exit_reason = KVM_EXIT_INTR;
 		goto out;
 	}
 
+	/*
+	 * down_read() may sleep and return with interrupts enabled
+	 */
+	down_read(&vcpu->kvm->slots_lock);
+
+	preempt_disable();
+	local_irq_disable();
+
 	vcpu->guest_mode = 1;
 	kvm_guest_enter();
-	down_read(&vcpu->kvm->slots_lock);
 	r = vti_vcpu_run(vcpu, kvm_run);
 	if (r < 0) {
 		local_irq_enable();