drm/i915/gvt: create an idle vGPU

vGPU resource is allocated by scheduler. To account for non-allocated
free cycles, we create an idle vGPU as the placeholder similar to idle task
concept, which is useful to handle some corner cases in scheduling policy.
Signed-off-by: Ping Gao <ping.a.gao@intel.com>
Reviewed-by: Kevin Tian <kevin.tian@intel.com>
Signed-off-by: Zhenyu Wang <zhenyuw@linux.intel.com>

drivers/gpu/drm/i915/gvt/gvt.c

@@ -202,6 +202,8 @@ void intel_gvt_clean_device(struct drm_i915_private *dev_priv)
 
 	idr_destroy(&gvt->vgpu_idr);
 
+	intel_gvt_destroy_idle_vgpu(gvt->idle_vgpu);
+
 	kfree(dev_priv->gvt);
 	dev_priv->gvt = NULL;
 }
@@ -220,6 +222,7 @@ void intel_gvt_clean_device(struct drm_i915_private *dev_priv)
 int intel_gvt_init_device(struct drm_i915_private *dev_priv)
 {
 	struct intel_gvt *gvt;
+	struct intel_vgpu *vgpu;
 	int ret;
 
 	/*
@@ -292,6 +295,14 @@ int intel_gvt_init_device(struct drm_i915_private *dev_priv)
 		goto out_clean_types;
 	}
 
+	vgpu = intel_gvt_create_idle_vgpu(gvt);
+	if (IS_ERR(vgpu)) {
+		ret = PTR_ERR(vgpu);
+		gvt_err("failed to create idle vgpu\n");
+		goto out_clean_types;
+	}
+	gvt->idle_vgpu = vgpu;
+
 	gvt_dbg_core("gvt device initialization is done\n");
 	dev_priv->gvt = gvt;
 	return 0;

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

@@ -243,6 +243,7 @@ struct intel_gvt {
 	DECLARE_HASHTABLE(cmd_table, GVT_CMD_HASH_BITS);
 	struct intel_vgpu_type *types;
 	unsigned int num_types;
+	struct intel_vgpu *idle_vgpu;
 
 	struct task_struct *service_thread;
 	wait_queue_head_t service_thread_wq;
@@ -386,6 +387,8 @@ static inline void intel_vgpu_write_pci_bar(struct intel_vgpu *vgpu,
 int intel_gvt_init_vgpu_types(struct intel_gvt *gvt);
 void intel_gvt_clean_vgpu_types(struct intel_gvt *gvt);
 
+struct intel_vgpu *intel_gvt_create_idle_vgpu(struct intel_gvt *gvt);
+void intel_gvt_destroy_idle_vgpu(struct intel_vgpu *vgpu);
 struct intel_vgpu *intel_gvt_create_vgpu(struct intel_gvt *gvt,
 					 struct intel_vgpu_type *type);
 void intel_gvt_destroy_vgpu(struct intel_vgpu *vgpu);

drivers/gpu/drm/i915/gvt/vgpu.c

@@ -233,6 +233,59 @@ void intel_gvt_destroy_vgpu(struct intel_vgpu *vgpu)
 	mutex_unlock(&gvt->lock);
 }
 
+#define IDLE_VGPU_IDR 0
+
+/**
+ * intel_gvt_create_idle_vgpu - create an idle virtual GPU
+ * @gvt: GVT device
+ *
+ * This function is called when user wants to create an idle virtual GPU.
+ *
+ * Returns:
+ * pointer to intel_vgpu, error pointer if failed.
+ */
+struct intel_vgpu *intel_gvt_create_idle_vgpu(struct intel_gvt *gvt)
+{
+	struct intel_vgpu *vgpu;
+	enum intel_engine_id i;
+	int ret;
+
+	vgpu = vzalloc(sizeof(*vgpu));
+	if (!vgpu)
+		return ERR_PTR(-ENOMEM);
+
+	vgpu->id = IDLE_VGPU_IDR;
+	vgpu->gvt = gvt;
+
+	for (i = 0; i < I915_NUM_ENGINES; i++)
+		INIT_LIST_HEAD(&vgpu->workload_q_head[i]);
+
+	ret = intel_vgpu_init_sched_policy(vgpu);
+	if (ret)
+		goto out_free_vgpu;
+
+	vgpu->active = false;
+
+	return vgpu;
+
+out_free_vgpu:
+	vfree(vgpu);
+	return ERR_PTR(ret);
+}
+
+/**
+ * intel_gvt_destroy_vgpu - destroy an idle virtual GPU
+ * @vgpu: virtual GPU
+ *
+ * This function is called when user wants to destroy an idle virtual GPU.
+ *
+ */
+void intel_gvt_destroy_idle_vgpu(struct intel_vgpu *vgpu)
+{
+	intel_vgpu_clean_sched_policy(vgpu);
+	vfree(vgpu);
+}
+
 static struct intel_vgpu *__intel_gvt_create_vgpu(struct intel_gvt *gvt,
 		struct intel_vgpu_creation_params *param)
 {
@@ -249,7 +302,8 @@ static struct intel_vgpu *__intel_gvt_create_vgpu(struct intel_gvt *gvt,
 
 	mutex_lock(&gvt->lock);
 
-	ret = idr_alloc(&gvt->vgpu_idr, vgpu, 1, GVT_MAX_VGPU, GFP_KERNEL);
+	ret = idr_alloc(&gvt->vgpu_idr, vgpu, IDLE_VGPU_IDR + 1, GVT_MAX_VGPU,
+		GFP_KERNEL);
 	if (ret < 0)
 		goto out_free_vgpu;