vp_vdpa: report doorbell address

This patch reports the per vq doorbell location and size to vDPA
bus. Userspace can then map the doorbell via mmap() via vhost-vDPA bus
driver.
Signed-off-by: Jason Wang <jasowang@redhat.com>
Link: https://lore.kernel.org/r/20210415073147.19331-8-jasowang@redhat.comSigned-off-by: Michael S. Tsirkin <mst@redhat.com>
Reviewed-by: Eli Cohen <elic@nvidia.com>

drivers/vdpa/virtio_pci/vp_vdpa.c

@@ -26,6 +26,7 @@ struct vp_vring {
 	void __iomem *notify;
 	char msix_name[VP_VDPA_NAME_SIZE];
 	struct vdpa_callback cb;
+	resource_size_t notify_pa;
 	int irq;
 };
 
@@ -336,6 +337,19 @@ static void vp_vdpa_set_config_cb(struct vdpa_device *vdpa,
 	vp_vdpa->config_cb = *cb;
 }
 
+static struct vdpa_notification_area
+vp_vdpa_get_vq_notification(struct vdpa_device *vdpa, u16 qid)
+{
+	struct vp_vdpa *vp_vdpa = vdpa_to_vp(vdpa);
+	struct virtio_pci_modern_device *mdev = &vp_vdpa->mdev;
+	struct vdpa_notification_area notify;
+
+	notify.addr = vp_vdpa->vring[qid].notify_pa;
+	notify.size = mdev->notify_offset_multiplier;
+
+	return notify;
+}
+
 static const struct vdpa_config_ops vp_vdpa_ops = {
 	.get_features	= vp_vdpa_get_features,
 	.set_features	= vp_vdpa_set_features,
@@ -343,6 +357,7 @@ static const struct vdpa_config_ops vp_vdpa_ops = {
 	.set_status	= vp_vdpa_set_status,
 	.get_vq_num_max	= vp_vdpa_get_vq_num_max,
 	.get_vq_state	= vp_vdpa_get_vq_state,
+	.get_vq_notification = vp_vdpa_get_vq_notification,
 	.set_vq_state	= vp_vdpa_set_vq_state,
 	.set_vq_cb	= vp_vdpa_set_vq_cb,
 	.set_vq_ready	= vp_vdpa_set_vq_ready,
@@ -416,7 +431,8 @@ static int vp_vdpa_probe(struct pci_dev *pdev, const struct pci_device_id *id)
 	for (i = 0; i < vp_vdpa->queues; i++) {
 		vp_vdpa->vring[i].irq = VIRTIO_MSI_NO_VECTOR;
 		vp_vdpa->vring[i].notify =
-			vp_modern_map_vq_notify(mdev, i, NULL);
+			vp_modern_map_vq_notify(mdev, i,
+						&vp_vdpa->vring[i].notify_pa);
 		if (!vp_vdpa->vring[i].notify) {
 			dev_warn(&pdev->dev, "Fail to map vq notify %d\n", i);
 			goto err;