vdpa_sim: use kthread worker

Let's use our own kthread to run device jobs.
This allows us more flexibility, especially we can attach the kthread
to the user address space when vDPA uses user's VA.
Acked-by: Jason Wang <jasowang@redhat.com>
Signed-off-by: Stefano Garzarella <sgarzare@redhat.com>
Message-Id: <20230404131725.45908-1-sgarzare@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>

drivers/vdpa/vdpa_sim/vdpa_sim.c

@@ -11,8 +11,8 @@
 #include <linux/module.h>
 #include <linux/device.h>
 #include <linux/kernel.h>
+#include <linux/kthread.h>
 #include <linux/slab.h>
-#include <linux/sched.h>
 #include <linux/dma-map-ops.h>
 #include <linux/vringh.h>
 #include <linux/vdpa.h>
@@ -127,7 +127,7 @@ static void vdpasim_do_reset(struct vdpasim *vdpasim)
 static const struct vdpa_config_ops vdpasim_config_ops;
 static const struct vdpa_config_ops vdpasim_batch_config_ops;
 
-static void vdpasim_work_fn(struct work_struct *work)
+static void vdpasim_work_fn(struct kthread_work *work)
 {
 	struct vdpasim *vdpasim = container_of(work, struct vdpasim, work);
 
@@ -170,11 +170,17 @@ struct vdpasim *vdpasim_create(struct vdpasim_dev_attr *dev_attr,
 
 	vdpasim = vdpa_to_sim(vdpa);
 	vdpasim->dev_attr = *dev_attr;
-	INIT_WORK(&vdpasim->work, vdpasim_work_fn);
+	dev = &vdpasim->vdpa.dev;
+
+	kthread_init_work(&vdpasim->work, vdpasim_work_fn);
+	vdpasim->worker = kthread_create_worker(0, "vDPA sim worker: %s",
+						dev_attr->name);
+	if (IS_ERR(vdpasim->worker))
+		goto err_iommu;
+
 	spin_lock_init(&vdpasim->lock);
 	spin_lock_init(&vdpasim->iommu_lock);
 
-	dev = &vdpasim->vdpa.dev;
 	dev->dma_mask = &dev->coherent_dma_mask;
 	if (dma_set_mask_and_coherent(dev, DMA_BIT_MASK(64)))
 		goto err_iommu;
@@ -223,7 +229,7 @@ EXPORT_SYMBOL_GPL(vdpasim_create);
 
 void vdpasim_schedule_work(struct vdpasim *vdpasim)
 {
-	schedule_work(&vdpasim->work);
+	kthread_queue_work(vdpasim->worker, &vdpasim->work);
 }
 EXPORT_SYMBOL_GPL(vdpasim_schedule_work);
 
@@ -623,7 +629,8 @@ static void vdpasim_free(struct vdpa_device *vdpa)
 	struct vdpasim *vdpasim = vdpa_to_sim(vdpa);
 	int i;
 
-	cancel_work_sync(&vdpasim->work);
+	kthread_cancel_work_sync(&vdpasim->work);
+	kthread_destroy_worker(vdpasim->worker);
 
 	for (i = 0; i < vdpasim->dev_attr.nvqs; i++) {
 		vringh_kiov_cleanup(&vdpasim->vqs[i].out_iov);

drivers/vdpa/vdpa_sim/vdpa_sim.h

@@ -57,7 +57,8 @@ struct vdpasim_dev_attr {
 struct vdpasim {
 	struct vdpa_device vdpa;
 	struct vdpasim_virtqueue *vqs;
-	struct work_struct work;
+	struct kthread_worker *worker;
+	struct kthread_work work;
 	struct vdpasim_dev_attr dev_attr;
 	/* spinlock to synchronize virtqueue state */
 	spinlock_t lock;