[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.$B!!(B(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>