[PATCH] KVM: Initialize kvm_arch_ops on unload

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.

Signed-off-by: Avi Kivity <avi@qumranet.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

1 files changed, 6 insertions, 0 deletions

diff --git a/drivers/kvm/kvm_main.c b/drivers/kvm/kvm_main.c
index 38375e2..0631407 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 -EEXIST;
+	}
+
 	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)