[PATCH] kvm: initialize kvm_arch_ops in kvm_init()

The latest version of kvm doesn't initialize kvm_arch_ops in kvm_init(), 
which causes an error with the following sequence.

1. Load the supported arch's module.
2. Load the unsupported arch's module.　(loading error)
3. Unload the unsupported arch's module.

You'll get the following error message after step 3.
"BUG: unable to handle to handle kernel paging request at virtual 
address xxxxxxxx"

The problem here is that the unsupported arch's module overwrites 
kvm_arch_ops of the supported arch's module at step 2.

This patch initializes kvm_arch_ops upon loading architecture specific 
kvm module, and prevents overwriting kvm_arch_ops when kvm_arch_ops is 
already set correctly.


-------------------------------------------------------------------
diff --git a/drivers/kvm/kvm_main.c b/drivers/kvm/kvm_main.c
index 9f24f22..9287b2d 100644
--- a/drivers/kvm/kvm_main.c
+++ b/drivers/kvm/kvm_main.c
@@ -1865,6 +1865,11 @@ int kvm_init_arch(struct kvm_arch_ops *ops, 
struct module *module)
 {
        int r;
 
+       if ( kvm_arch_ops ) {
+               printk(KERN_ERR "kvm: already loaded the other module\n
");
+               return -EOPNOTSUPP;
+       }
+
        kvm_arch_ops = ops;
 
        if (!kvm_arch_ops->cpu_has_kvm_support()) {
@@ -1907,6 +1912,7 @@ void kvm_exit_arch(void)
        unregister_reboot_notifier(&kvm_reboot_notifier);
        on_each_cpu(kvm_arch_ops->hardware_disable, 0, 0, 1);
        kvm_arch_ops->hardware_unsetup();
+       kvm_arch_ops = NULL;
 }
 
 static __init int kvm_init(void)
@@ -1914,6 +1920,7 @@ static __init int kvm_init(void)
        static struct page *bad_page;
        int r = 0;
 
+       kvm_arch_ops = NULL;
        kvm_init_debug();
 
        kvm_init_msr_list();


--
Yoshimi Ichiyanagi
Open source software computing project, NTT Cyber Space Laboratories
E-mail : ichiyanagi.yoshimi@xxxxxxxxxxxxx

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