virtio: hand virtio ring alignment as argument to vring_new_virtqueue

This allows each virtio user to hand in the alignment appropriate to
their virtio_ring structures.

Signed-off-by: Rusty Russell <[e-mail]>
Acked-by: Christian Borntraeger <[e-mail]>

drivers/lguest/lguest_device.c

···
 
 	/* OK, tell virtio_ring.c to set up a virtqueue now we know its size
 	 * and we've got a pointer to its pages. */
-	vq = vring_new_virtqueue(lvq->config.num, vdev, lvq->pages,
-				 lg_notify, callback);
+	vq = vring_new_virtqueue(lvq->config.num, LGUEST_VRING_ALIGN,
+				 vdev, lvq->pages, lg_notify, callback);
 	if (!vq) {
 		err = -ENOMEM;
 		goto unmap;

drivers/s390/kvm/kvm_virtio.c

···
 	if (err)
 		goto out;
 
-	vq = vring_new_virtqueue(config->num, vdev, (void *) config->address,
+	vq = vring_new_virtqueue(config->num, KVM_S390_VIRTIO_RING_ALIGN,
+				 vdev, (void *) config->address,
 				 kvm_notify, callback);
 	if (!vq) {
 		err = -ENOMEM;

drivers/virtio/virtio_pci.c

···
 		  vp_dev->ioaddr + VIRTIO_PCI_QUEUE_PFN);
 
 	/* create the vring */
-	vq = vring_new_virtqueue(info->num, vdev, info->queue,
-				 vp_notify, callback);
+	vq = vring_new_virtqueue(info->num, VIRTIO_PCI_VRING_ALIGN,
+				 vdev, info->queue, vp_notify, callback);
 	if (!vq) {
 		err = -ENOMEM;
 		goto out_activate_queue;

drivers/virtio/virtio_ring.c

···
 };
 
 struct virtqueue *vring_new_virtqueue(unsigned int num,
+				      unsigned int vring_align,
 				      struct virtio_device *vdev,
 				      void *pages,
 				      void (*notify)(struct virtqueue *),
···
 	if (!vq)
 		return NULL;
 
-	vring_init(&vq->vring, num, pages, PAGE_SIZE);
+	vring_init(&vq->vring, num, pages, vring_align);
 	vq->vq.callback = callback;
 	vq->vq.vdev = vdev;
 	vq->vq.vq_ops = &vring_vq_ops;

include/linux/virtio_ring.h

···
 struct virtqueue;
 
 struct virtqueue *vring_new_virtqueue(unsigned int num,
+				      unsigned int vring_align,
 				      struct virtio_device *vdev,
 				      void *pages,
 				      void (*notify)(struct virtqueue *vq),