virtio_pci_modern: treat vp_dev->admin_vq.info.vq pointer as static

It is guaranteed by the virtio_pci and PCI layers that none of the VFs
is probed before setup_vq() is called for admin queue and after del_vq()
is called for admin queue. Therefore treat vp_dev->admin_vq.info.vq as
static, don't null it and don't take cmd lock during assign.

Signed-off-by: Jiri Pirko <jiri@nvidia.com>
Message-Id: <20240716113552.80599-7-jiri@resnulli.us>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>

Author: Jiri Pirko

drivers/virtio/virtio_pci_common.h

@@ -45,7 +45,7 @@ struct virtio_pci_vq_info {
 struct virtio_pci_admin_vq {
 	/* Virtqueue info associated with this admin queue. */
 	struct virtio_pci_vq_info info;
-	/* serializing admin commands execution and virtqueue deletion */
+	/* serializing admin commands execution. */
 	struct mutex cmd_lock;
 	u64 supported_cmds;
 	/* Name of the admin queue: avq.$vq_index. */

drivers/virtio/virtio_pci_modern.c

@@ -580,11 +580,8 @@ static struct virtqueue *setup_vq(struct virtio_pci_device *vp_dev,
 		goto err;
 	}
 
-	if (is_avq) {
-		mutex_lock(&vp_dev->admin_vq.cmd_lock);
+	if (is_avq)
 		vp_dev->admin_vq.info.vq = vq;
-		mutex_unlock(&vp_dev->admin_vq.cmd_lock);
-	}
 
 	return vq;
 
@@ -620,12 +617,6 @@ static void del_vq(struct virtio_pci_vq_info *info)
 	struct virtio_pci_device *vp_dev = to_vp_device(vq->vdev);
 	struct virtio_pci_modern_device *mdev = &vp_dev->mdev;
 
-	if (vp_is_avq(&vp_dev->vdev, vq->index)) {
-		mutex_lock(&vp_dev->admin_vq.cmd_lock);
-		vp_dev->admin_vq.info.vq = NULL;
-		mutex_unlock(&vp_dev->admin_vq.cmd_lock);
-	}
-
 	if (vp_dev->msix_enabled)
 		vp_modern_queue_vector(mdev, vq->index,
 				       VIRTIO_MSI_NO_VECTOR);