virtio-pci-modern: introduce vp_modern_set_queue_vector()

This patch introduces a helper to set virtqueue MSI vector.
Signed-off-by: Jason Wang <jasowang@redhat.com>
Link: https://lore.kernel.org/r/20210104065503.199631-10-jasowang@redhat.comSigned-off-by: Michael S. Tsirkin <mst@redhat.com>

drivers/virtio/virtio_pci_modern.c

@@ -191,6 +191,25 @@ static void vp_modern_set_features(struct virtio_pci_modern_device *mdev,
 	vp_iowrite32(features >> 32, &cfg->guest_feature);
 }
 
+/*
+ * vp_modern_queue_vector - set the MSIX vector for a specific virtqueue
+ * @mdev: the modern virtio-pci device
+ * @index: queue index
+ * @vector: the config vector
+ *
+ * Returns the config vector read from the device
+ */
+static u16 vp_modern_queue_vector(struct virtio_pci_modern_device *mdev,
+				  u16 index, u16 vector)
+{
+	struct virtio_pci_common_cfg __iomem *cfg = mdev->common;
+
+	vp_iowrite16(index, &cfg->queue_select);
+	vp_iowrite16(vector, &cfg->queue_msix_vector);
+	/* Flush the write out to device */
+	return vp_ioread16(&cfg->queue_msix_vector);
+}
+
 /* virtio config->finalize_features() implementation */
 static int vp_finalize_features(struct virtio_device *vdev)
 {
@@ -474,8 +493,7 @@ static struct virtqueue *setup_vq(struct virtio_pci_device *vp_dev,
 	}
 
 	if (msix_vec != VIRTIO_MSI_NO_VECTOR) {
-		vp_iowrite16(msix_vec, &cfg->queue_msix_vector);
-		msix_vec = vp_ioread16(&cfg->queue_msix_vector);
+		msix_vec = vp_modern_queue_vector(mdev, index, msix_vec);
 		if (msix_vec == VIRTIO_MSI_NO_VECTOR) {
 			err = -EBUSY;
 			goto err_assign_vector;
@@ -522,17 +540,10 @@ static void del_vq(struct virtio_pci_vq_info *info)
 	struct virtqueue *vq = info->vq;
 	struct virtio_pci_device *vp_dev = to_vp_device(vq->vdev);
 	struct virtio_pci_modern_device *mdev = &vp_dev->mdev;
-	struct virtio_pci_common_cfg __iomem *cfg = mdev->common;
-
 
-	vp_iowrite16(vq->index, &cfg->queue_select);
-
-	if (vp_dev->msix_enabled) {
-		vp_iowrite16(VIRTIO_MSI_NO_VECTOR,
-			     &cfg->queue_msix_vector);
-		/* Flush the write out to device */
-		vp_ioread16(&cfg->queue_msix_vector);
-	}
+	if (vp_dev->msix_enabled)
+		vp_modern_queue_vector(mdev, vq->index,
+				       VIRTIO_MSI_NO_VECTOR);
 
 	if (!mdev->notify_base)
 		pci_iounmap(mdev->pci_dev, (void __force __iomem *)vq->priv);