drm/i915/gvt: Add basic debugfs infrastructure

We need debugfs entry to expose some debug information of gvt and vGPUs.
The first tool will be added is mmio-diff, which help to find the
difference values of host and vGPU mmio. It's useful for platform
enabling.

This patch just add a basic debugfs infrastructure, each vGPU has its own
sub-folder. Two simple attributes are created as a template.
.
├── num_tracked_mmio
├── vgpu1
|   └── active
└── vgpu2
    └── active

Signed-off-by: Changbin Du <changbin.du@intel.com>
Reviewed-by: Zhi Wang <zhi.a.wang@intel.com>
Signed-off-by: Zhi Wang <zhi.a.wang@intel.com>

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

@@ -190,6 +190,8 @@ struct intel_vgpu {
 	struct intel_vgpu_display display;
 	struct intel_vgpu_submission submission;
 
+	struct dentry *debugfs;
+
 #if IS_ENABLED(CONFIG_DRM_I915_GVT_KVMGT)
 	struct {
 		struct mdev_device *mdev;
@@ -253,7 +255,7 @@ struct intel_gvt_mmio {
 	unsigned int num_mmio_block;
 
 	DECLARE_HASHTABLE(mmio_info_table, INTEL_GVT_MMIO_HASH_BITS);
-	unsigned int num_tracked_mmio;
+	unsigned long num_tracked_mmio;
 };
 
 struct intel_gvt_firmware {
@@ -301,6 +303,8 @@ struct intel_gvt {
 	struct task_struct *service_thread;
 	wait_queue_head_t service_thread_wq;
 	unsigned long service_request;
+
+	struct dentry *debugfs_root;
 };
 
 static inline struct intel_gvt *to_gvt(struct drm_i915_private *i915)
@@ -619,6 +623,12 @@ static inline bool intel_gvt_mmio_has_mode_mask(
 	return gvt->mmio.mmio_attribute[offset >> 2] & F_MODE_MASK;
 }
 
+int intel_gvt_debugfs_add_vgpu(struct intel_vgpu *vgpu);
+void intel_gvt_debugfs_remove_vgpu(struct intel_vgpu *vgpu);
+int intel_gvt_debugfs_init(struct intel_gvt *gvt);
+void intel_gvt_debugfs_clean(struct intel_gvt *gvt);
+
+
 #include "trace.h"
 #include "mpt.h"