drm/i915/gvt: Change KVMGT as self load module

This trys to make 'kvmgt' module as self loadable instead of loading
by i915/gvt device model. So hypervisor specific module could be
stand-alone, e.g only after loading hypervisor specific module, GVT
feature could be enabled via specific hypervisor interface, e.g VFIO/mdev.

So this trys to use hypervisor module register/unregister interface
for that. Hypervisor module needs to take care of module reference
itself when working for hypervisor interface, e.g for VFIO/mdev,
hypervisor module would reference counting mdev when open and release.

This makes 'kvmgt' module really split from GVT device model. User
needs to load 'kvmgt' to enable VFIO/mdev interface.

v6:
- remove unused variable

v5:
- put module reference in register error path

v4:
- fix checkpatch warning

v3:
- Fix module reference handling for device open and release. Unused
  mdev devices would be cleaned up in device unregister when module unload.

v2:
- Fix kvmgt order after i915 for built-in case

Cc: "Yuan, Hang" <hang.yuan@intel.com>
Cc: Alex Williamson <alex.williamson@redhat.com>
Cc: "He, Min" <min.he@intel.com>
Reviewed-by: Yuan, Hang <hang.yuan@intel.com>
Acked-by: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
Signed-off-by: Zhenyu Wang <zhenyuw@linux.intel.com>

1 files changed, 14 insertions, 2 deletions

diff --git a/drivers/gpu/drm/i915/gvt/kvmgt.c b/drivers/gpu/drm/i915/gvt/kvmgt.c
index 1bbd04d30c42..a19e684e621a 100644
--- a/drivers/gpu/drm/i915/gvt/kvmgt.c
+++ b/drivers/gpu/drm/i915/gvt/kvmgt.c
@@ -627,6 +627,12 @@ static int intel_vgpu_open(struct mdev_device *mdev)
 		goto undo_iommu;
 	}
 
+	/* Take a module reference as mdev core doesn't take
+	 * a reference for vendor driver.
+	 */
+	if (!try_module_get(THIS_MODULE))
+		goto undo_group;
+
 	ret = kvmgt_guest_init(mdev);
 	if (ret)
 		goto undo_group;
@@ -679,6 +685,9 @@ static void __intel_vgpu_release(struct intel_vgpu *vgpu)
 					&vgpu->vdev.group_notifier);
 	WARN(ret, "vfio_unregister_notifier for group failed: %d\n", ret);
 
+	/* dereference module reference taken at open */
+	module_put(THIS_MODULE);
+
 	info = (struct kvmgt_guest_info *)vgpu->handle;
 	kvmgt_guest_exit(info);
 
@@ -1849,7 +1858,8 @@ static bool kvmgt_is_valid_gfn(unsigned long handle, unsigned long gfn)
 	return ret;
 }
 
-struct intel_gvt_mpt kvmgt_mpt = {
+static struct intel_gvt_mpt kvmgt_mpt = {
+	.type = INTEL_GVT_HYPERVISOR_KVM,
 	.host_init = kvmgt_host_init,
 	.host_exit = kvmgt_host_exit,
 	.attach_vgpu = kvmgt_attach_vgpu,
@@ -1868,15 +1878,17 @@ struct intel_gvt_mpt kvmgt_mpt = {
 	.put_vfio_device = kvmgt_put_vfio_device,
 	.is_valid_gfn = kvmgt_is_valid_gfn,
 };
-EXPORT_SYMBOL_GPL(kvmgt_mpt);
 
 static int __init kvmgt_init(void)
 {
+	if (intel_gvt_register_hypervisor(&kvmgt_mpt) < 0)
+		return -ENODEV;
 	return 0;
 }
 
 static void __exit kvmgt_exit(void)
 {
+	intel_gvt_unregister_hypervisor();
 }
 
 module_init(kvmgt_init);