drm/i915/gvt/kvmgt: add vfio/mdev support to KVMGT

KVMGT leverages vfio/mdev to mediate device accesses from guest,
this patch adds the vfio/mdev support, thereby completes the
functionality. An intel_vgpu is presented as a mdev device,
and full userspace API compatibility with vfio-pci is kept.
An intel_vgpu_ops is provided to mdev framework, methods get
called to create/remove a vgpu, to open/close it, and to
access it.

Signed-off-by: Kevin Tian <kevin.tian@intel.com>
Signed-off-by: Xiaoguang Chen <xiaoguang.chen@intel.com>
Signed-off-by: Jike Song <jike.song@intel.com>
Signed-off-by: Zhenyu Wang <zhenyuw@linux.intel.com>

drivers/gpu/drm/i915/Kconfig

@@ -116,6 +116,7 @@ config DRM_I915_GVT_KVMGT
 	tristate "Enable KVM/VFIO support for Intel GVT-g"
 	depends on DRM_I915_GVT
 	depends on KVM
+	depends on VFIO_MDEV && VFIO_MDEV_DEVICE
 	default n
 	help
 	  Choose this option if you want to enable KVMGT support for

drivers/gpu/drm/i915/gvt/Makefile

@@ -5,6 +5,4 @@ GVT_SOURCE := gvt.o aperture_gm.o handlers.o vgpu.o trace_points.o firmware.o \
 
 ccflags-y				+= -I$(src) -I$(src)/$(GVT_DIR) -Wall
 i915-y					+= $(addprefix $(GVT_DIR)/, $(GVT_SOURCE))
-
-CFLAGS_kvmgt.o				:= -Wno-unused-function
 obj-$(CONFIG_DRM_I915_GVT_KVMGT)	+= $(GVT_DIR)/kvmgt.o

drivers/gpu/drm/i915/gvt/gvt.h

@@ -164,15 +164,17 @@ struct intel_vgpu {
 
 #if IS_ENABLED(CONFIG_DRM_I915_GVT_KVMGT)
 	struct {
-		struct device *mdev;
+		struct mdev_device *mdev;
 		struct vfio_region *region;
 		int num_regions;
 		struct eventfd_ctx *intx_trigger;
 		struct eventfd_ctx *msi_trigger;
 		struct rb_root cache;
 		struct mutex cache_lock;
-		void *vfio_group;
 		struct notifier_block iommu_notifier;
+		struct notifier_block group_notifier;
+		struct kvm *kvm;
+		struct work_struct release_work;
 	} vdev;
 #endif
 };