[PATCH] KVM: Recover after an arch module load failure

If we load the wrong arch module, it leaves behind kvm_arch_ops set, which
prevents loading of the correct arch module later.

Fix be not setting kvm_arch_ops until we're sure it's good.

Signed-off-by: Yoshimi Ichiyanagi <ichiyanagi.yoshimi@lab.ntt.co.jp>
Signed-off-by: Avi Kivity <avi@qumranet.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

drivers/kvm/kvm_main.c

@@ -1944,17 +1944,17 @@ int kvm_init_arch(struct kvm_arch_ops *ops, struct module *module)
 		return -EEXIST;
 	}
 
-	kvm_arch_ops = ops;
-
-	if (!kvm_arch_ops->cpu_has_kvm_support()) {
+	if (!ops->cpu_has_kvm_support()) {
 		printk(KERN_ERR "kvm: no hardware support\n");
 		return -EOPNOTSUPP;
 	}
-	if (kvm_arch_ops->disabled_by_bios()) {
+	if (ops->disabled_by_bios()) {
 		printk(KERN_ERR "kvm: disabled by bios\n");
 		return -EOPNOTSUPP;
 	}
 
+	kvm_arch_ops = ops;
+
 	r = kvm_arch_ops->hardware_setup();
 	if (r < 0)
 	    return r;