drm/i915/gvt: Activate/de-activate vGPU in mdev ops.

This patch introduces two functions for activating/de-activating vGPU in
mdev ops.

A racing condition was found between virtual vblank emulation and KVGMT
mdev release path. V-blank emulation will emulate and inject V-blank
interrupt for every active vGPU with holding gvt->lock, while in mdev
release path, it will directly release hypervisor handle without changing
vGPU status or taking gvt->lock, so a kernel oops is encountered when
vblank emulation is injecting a interrupt with a invalid hypervisor
handle. (Reported by Terrence)

To solve this problem, we factor out vGPU activation/de-activation from
vGPU creation/destruction path and let KVMGT mdev release ops de-activate
the vGPU before release hypervisor handle. Once a vGPU is de-activated,
GVT-g will not emulate v-blank for it or touch the hypervisor handle.

Fixes: 659643f7 ("drm/i915/gvt/kvmgt: add vfio/mdev support to KVMGT")
Signed-off-by: Zhi Wang <zhi.a.wang@intel.com>
Signed-off-by: Zhenyu Wang <zhenyuw@linux.intel.com>

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

@@ -52,6 +52,8 @@ static const struct intel_gvt_ops intel_gvt_ops = {
 	.vgpu_create = intel_gvt_create_vgpu,
 	.vgpu_destroy = intel_gvt_destroy_vgpu,
 	.vgpu_reset = intel_gvt_reset_vgpu,
+	.vgpu_activate = intel_gvt_activate_vgpu,
+	.vgpu_deactivate = intel_gvt_deactivate_vgpu,
 };
 
 /**

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

@@ -382,7 +382,8 @@ void intel_gvt_destroy_vgpu(struct intel_vgpu *vgpu);
 void intel_gvt_reset_vgpu_locked(struct intel_vgpu *vgpu, bool dmlr,
 				 unsigned int engine_mask);
 void intel_gvt_reset_vgpu(struct intel_vgpu *vgpu);
-
+void intel_gvt_activate_vgpu(struct intel_vgpu *vgpu);
+void intel_gvt_deactivate_vgpu(struct intel_vgpu *vgpu);
 
 /* validating GM functions */
 #define vgpu_gmadr_is_aperture(vgpu, gmadr) \
@@ -449,6 +450,8 @@ struct intel_gvt_ops {
 				struct intel_vgpu_type *);
 	void (*vgpu_destroy)(struct intel_vgpu *);
 	void (*vgpu_reset)(struct intel_vgpu *);
+	void (*vgpu_activate)(struct intel_vgpu *);
+	void (*vgpu_deactivate)(struct intel_vgpu *);
 };
 
 

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

@@ -544,6 +544,8 @@ static int intel_vgpu_open(struct mdev_device *mdev)
 	if (ret)
 		goto undo_group;
 
+	intel_gvt_ops->vgpu_activate(vgpu);
+
 	atomic_set(&vgpu->vdev.released, 0);
 	return ret;
 
@@ -569,6 +571,8 @@ static void __intel_vgpu_release(struct intel_vgpu *vgpu)
 	if (atomic_cmpxchg(&vgpu->vdev.released, 0, 1))
 		return;
 
+	intel_gvt_ops->vgpu_deactivate(vgpu);
+
 	ret = vfio_unregister_notifier(mdev_dev(vgpu->vdev.mdev), VFIO_IOMMU_NOTIFY,
 					&vgpu->vdev.iommu_notifier);
 	WARN(ret, "vfio_unregister_notifier for iommu failed: %d\n", ret);

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

@@ -179,20 +179,34 @@ static void intel_gvt_update_vgpu_types(struct intel_gvt *gvt)
 }
 
 /**
- * intel_gvt_destroy_vgpu - destroy a virtual GPU
+ * intel_gvt_active_vgpu - activate a virtual GPU
  * @vgpu: virtual GPU
  *
- * This function is called when user wants to destroy a virtual GPU.
+ * This function is called when user wants to activate a virtual GPU.
  *
  */
-void intel_gvt_destroy_vgpu(struct intel_vgpu *vgpu)
+void intel_gvt_activate_vgpu(struct intel_vgpu *vgpu)
+{
+	mutex_lock(&vgpu->gvt->lock);
+	vgpu->active = true;
+	mutex_unlock(&vgpu->gvt->lock);
+}
+
+/**
+ * intel_gvt_deactive_vgpu - deactivate a virtual GPU
+ * @vgpu: virtual GPU
+ *
+ * This function is called when user wants to deactivate a virtual GPU.
+ * All virtual GPU runtime information will be destroyed.
+ *
+ */
+void intel_gvt_deactivate_vgpu(struct intel_vgpu *vgpu)
 {
 	struct intel_gvt *gvt = vgpu->gvt;
 
 	mutex_lock(&gvt->lock);
 
 	vgpu->active = false;
-	idr_remove(&gvt->vgpu_idr, vgpu->id);
 
 	if (atomic_read(&vgpu->running_workload_num)) {
 		mutex_unlock(&gvt->lock);
@@ -201,6 +215,26 @@ void intel_gvt_destroy_vgpu(struct intel_vgpu *vgpu)
 	}
 
 	intel_vgpu_stop_schedule(vgpu);
+
+	mutex_unlock(&gvt->lock);
+}
+
+/**
+ * intel_gvt_destroy_vgpu - destroy a virtual GPU
+ * @vgpu: virtual GPU
+ *
+ * This function is called when user wants to destroy a virtual GPU.
+ *
+ */
+void intel_gvt_destroy_vgpu(struct intel_vgpu *vgpu)
+{
+	struct intel_gvt *gvt = vgpu->gvt;
+
+	mutex_lock(&gvt->lock);
+
+	WARN(vgpu->active, "vGPU is still active!\n");
+
+	idr_remove(&gvt->vgpu_idr, vgpu->id);
 	intel_vgpu_clean_sched_policy(vgpu);
 	intel_vgpu_clean_gvt_context(vgpu);
 	intel_vgpu_clean_execlist(vgpu);
@@ -277,7 +311,6 @@ static struct intel_vgpu *__intel_gvt_create_vgpu(struct intel_gvt *gvt,
 	if (ret)
 		goto out_clean_shadow_ctx;
 
-	vgpu->active = true;
 	mutex_unlock(&gvt->lock);
 
 	return vgpu;