vdpa_sim: replace the spinlock with a mutex to protect the state

The spinlock we use to protect the state of the simulator is sometimes
held for a long time (for example, when devices handle requests).

This also prevents us from calling functions that might sleep (such as
kthread_flush_work() in the next patch), and thus having to release
and retake the lock.

For these reasons, let's replace the spinlock with a mutex that gives
us more flexibility.

Suggested-by: Jason Wang <jasowang@redhat.com>
Acked-by: Jason Wang <jasowang@redhat.com>
Signed-off-by: Stefano Garzarella <sgarzare@redhat.com>
Message-Id: <20230404131730.45920-1-sgarzare@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>

drivers/vdpa/vdpa_sim/vdpa_sim.c

@@ -178,7 +178,7 @@ struct vdpasim *vdpasim_create(struct vdpasim_dev_attr *dev_attr,
 	if (IS_ERR(vdpasim->worker))
 		goto err_iommu;
 
-	spin_lock_init(&vdpasim->lock);
+	mutex_init(&vdpasim->mutex);
 	spin_lock_init(&vdpasim->iommu_lock);
 
 	dev->dma_mask = &dev->coherent_dma_mask;
@@ -286,13 +286,13 @@ static void vdpasim_set_vq_ready(struct vdpa_device *vdpa, u16 idx, bool ready)
 	struct vdpasim_virtqueue *vq = &vdpasim->vqs[idx];
 	bool old_ready;
 
-	spin_lock(&vdpasim->lock);
+	mutex_lock(&vdpasim->mutex);
 	old_ready = vq->ready;
 	vq->ready = ready;
 	if (vq->ready && !old_ready) {
 		vdpasim_queue_ready(vdpasim, idx);
 	}
-	spin_unlock(&vdpasim->lock);
+	mutex_unlock(&vdpasim->mutex);
 }
 
 static bool vdpasim_get_vq_ready(struct vdpa_device *vdpa, u16 idx)
@@ -310,9 +310,9 @@ static int vdpasim_set_vq_state(struct vdpa_device *vdpa, u16 idx,
 	struct vdpasim_virtqueue *vq = &vdpasim->vqs[idx];
 	struct vringh *vrh = &vq->vring;
 
-	spin_lock(&vdpasim->lock);
+	mutex_lock(&vdpasim->mutex);
 	vrh->last_avail_idx = state->split.avail_index;
-	spin_unlock(&vdpasim->lock);
+	mutex_unlock(&vdpasim->mutex);
 
 	return 0;
 }
@@ -409,9 +409,9 @@ static u8 vdpasim_get_status(struct vdpa_device *vdpa)
 	struct vdpasim *vdpasim = vdpa_to_sim(vdpa);
 	u8 status;
 
-	spin_lock(&vdpasim->lock);
+	mutex_lock(&vdpasim->mutex);
 	status = vdpasim->status;
-	spin_unlock(&vdpasim->lock);
+	mutex_unlock(&vdpasim->mutex);
 
 	return status;
 }
@@ -420,19 +420,19 @@ static void vdpasim_set_status(struct vdpa_device *vdpa, u8 status)
 {
 	struct vdpasim *vdpasim = vdpa_to_sim(vdpa);
 
-	spin_lock(&vdpasim->lock);
+	mutex_lock(&vdpasim->mutex);
 	vdpasim->status = status;
-	spin_unlock(&vdpasim->lock);
+	mutex_unlock(&vdpasim->mutex);
 }
 
 static int vdpasim_reset(struct vdpa_device *vdpa)
 {
 	struct vdpasim *vdpasim = vdpa_to_sim(vdpa);
 
-	spin_lock(&vdpasim->lock);
+	mutex_lock(&vdpasim->mutex);
 	vdpasim->status = 0;
 	vdpasim_do_reset(vdpasim);
-	spin_unlock(&vdpasim->lock);
+	mutex_unlock(&vdpasim->mutex);
 
 	return 0;
 }
@@ -441,9 +441,9 @@ static int vdpasim_suspend(struct vdpa_device *vdpa)
 {
 	struct vdpasim *vdpasim = vdpa_to_sim(vdpa);
 
-	spin_lock(&vdpasim->lock);
+	mutex_lock(&vdpasim->mutex);
 	vdpasim->running = false;
-	spin_unlock(&vdpasim->lock);
+	mutex_unlock(&vdpasim->mutex);
 
 	return 0;
 }
@@ -453,7 +453,7 @@ static int vdpasim_resume(struct vdpa_device *vdpa)
 	struct vdpasim *vdpasim = vdpa_to_sim(vdpa);
 	int i;
 
-	spin_lock(&vdpasim->lock);
+	mutex_lock(&vdpasim->mutex);
 	vdpasim->running = true;
 
 	if (vdpasim->pending_kick) {
@@ -464,7 +464,7 @@ static int vdpasim_resume(struct vdpa_device *vdpa)
 		vdpasim->pending_kick = false;
 	}
 
-	spin_unlock(&vdpasim->lock);
+	mutex_unlock(&vdpasim->mutex);
 
 	return 0;
 }
@@ -536,14 +536,14 @@ static int vdpasim_set_group_asid(struct vdpa_device *vdpa, unsigned int group,
 
 	iommu = &vdpasim->iommu[asid];
 
-	spin_lock(&vdpasim->lock);
+	mutex_lock(&vdpasim->mutex);
 
 	for (i = 0; i < vdpasim->dev_attr.nvqs; i++)
 		if (vdpasim_get_vq_group(vdpa, i) == group)
 			vringh_set_iotlb(&vdpasim->vqs[i].vring, iommu,
 					 &vdpasim->iommu_lock);
 
-	spin_unlock(&vdpasim->lock);
+	mutex_unlock(&vdpasim->mutex);
 
 	return 0;
 }

drivers/vdpa/vdpa_sim/vdpa_sim.h

@@ -60,8 +60,8 @@ struct vdpasim {
 	struct kthread_worker *worker;
 	struct kthread_work work;
 	struct vdpasim_dev_attr dev_attr;
-	/* spinlock to synchronize virtqueue state */
-	spinlock_t lock;
+	/* mutex to synchronize virtqueue state */
+	struct mutex mutex;
 	/* virtio config according to device type */
 	void *config;
 	struct vhost_iotlb *iommu;

drivers/vdpa/vdpa_sim/vdpa_sim_blk.c

@@ -290,7 +290,7 @@ static void vdpasim_blk_work(struct vdpasim *vdpasim)
 	bool reschedule = false;
 	int i;
 
-	spin_lock(&vdpasim->lock);
+	mutex_lock(&vdpasim->mutex);
 
 	if (!(vdpasim->status & VIRTIO_CONFIG_S_DRIVER_OK))
 		goto out;
@@ -321,7 +321,7 @@ static void vdpasim_blk_work(struct vdpasim *vdpasim)
 		}
 	}
 out:
-	spin_unlock(&vdpasim->lock);
+	mutex_unlock(&vdpasim->mutex);
 
 	if (reschedule)
 		vdpasim_schedule_work(vdpasim);

drivers/vdpa/vdpa_sim/vdpa_sim_net.c

@@ -201,7 +201,7 @@ static void vdpasim_net_work(struct vdpasim *vdpasim)
 	u64 rx_drops = 0, rx_overruns = 0, rx_errors = 0, tx_errors = 0;
 	int err;
 
-	spin_lock(&vdpasim->lock);
+	mutex_lock(&vdpasim->mutex);
 
 	if (!vdpasim->running)
 		goto out;
@@ -264,7 +264,7 @@ static void vdpasim_net_work(struct vdpasim *vdpasim)
 	}
 
 out:
-	spin_unlock(&vdpasim->lock);
+	mutex_unlock(&vdpasim->mutex);
 
 	u64_stats_update_begin(&net->tx_stats.syncp);
 	net->tx_stats.pkts += tx_pkts;