vDPA/ifcvf: implement doorbell mapping for ifcvf

This commit implements doorbell mapping feature for ifcvf.
This feature maps the notify page to userspace, to eliminate
vmexit when kick a vq.

Signed-off-by: Zhu Lingshan <lingshan.zhu@intel.com>
Link: https://lore.kernel.org/r/20210602084550.289599-3-lingshan.zhu@intel.com
Acked-by: Jason Wang <jasowang@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>

drivers/vdpa/ifcvf/ifcvf_main.c

@@ -413,6 +413,21 @@ static int ifcvf_vdpa_get_vq_irq(struct vdpa_device *vdpa_dev,
 	return vf->vring[qid].irq;
 }
 
+static struct vdpa_notification_area ifcvf_get_vq_notification(struct vdpa_device *vdpa_dev,
+							       u16 idx)
+{
+	struct ifcvf_hw *vf = vdpa_to_vf(vdpa_dev);
+	struct vdpa_notification_area area;
+
+	area.addr = vf->vring[idx].notify_pa;
+	if (!vf->notify_off_multiplier)
+		area.size = PAGE_SIZE;
+	else
+		area.size = vf->notify_off_multiplier;
+
+	return area;
+}
+
 /*
  * IFCVF currently does't have on-chip IOMMU, so not
  * implemented set_map()/dma_map()/dma_unmap()
@@ -440,6 +455,7 @@ static const struct vdpa_config_ops ifc_vdpa_ops = {
 	.get_config	= ifcvf_vdpa_get_config,
 	.set_config	= ifcvf_vdpa_set_config,
 	.set_config_cb  = ifcvf_vdpa_set_config_cb,
+	.get_vq_notification = ifcvf_get_vq_notification,
 };
 
 static int ifcvf_probe(struct pci_dev *pdev, const struct pci_device_id *id)