KVM: convert bus to slots_lock

Use slots_lock to protect device list on the bus.  slots_lock is already
taken for read everywhere, so we only need to take it for write when
registering devices.  This is in preparation to removing in_range and
kvm->lock around it.

Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Avi Kivity <avi@redhat.com>
diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h
index 4ea42c9..96c8c0b 100644
--- a/include/linux/kvm_host.h
+++ b/include/linux/kvm_host.h
@@ -42,6 +42,7 @@
 
 #define KVM_USERSPACE_IRQ_SOURCE_ID	0
 
+struct kvm;
 struct kvm_vcpu;
 extern struct kmem_cache *kvm_vcpu_cache;
 
@@ -61,7 +62,9 @@
 void kvm_io_bus_destroy(struct kvm_io_bus *bus);
 struct kvm_io_device *kvm_io_bus_find_dev(struct kvm_io_bus *bus,
 					  gpa_t addr, int len, int is_write);
-void kvm_io_bus_register_dev(struct kvm_io_bus *bus,
+void __kvm_io_bus_register_dev(struct kvm_io_bus *bus,
+			       struct kvm_io_device *dev);
+void kvm_io_bus_register_dev(struct kvm *kvm, struct kvm_io_bus *bus,
 			     struct kvm_io_device *dev);
 
 struct kvm_vcpu {