virtio_pci: support enabling VFs

There is a new feature bit allocated in virtio spec to
support SR-IOV (Single Root I/O Virtualization):

https://github.com/oasis-tcs/virtio-spec/issues/11

This patch enables the support for this feature bit in
virtio driver.

Signed-off-by: Tiwei Bie <tiwei.bie@intel.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
diff --git a/drivers/virtio/virtio_pci_modern.c b/drivers/virtio/virtio_pci_modern.c
index 2555d80..07571da 100644
--- a/drivers/virtio/virtio_pci_modern.c
+++ b/drivers/virtio/virtio_pci_modern.c
@@ -153,14 +153,28 @@ static u64 vp_get_features(struct virtio_device *vdev)
 	return features;
 }
 
+static void vp_transport_features(struct virtio_device *vdev, u64 features)
+{
+	struct virtio_pci_device *vp_dev = to_vp_device(vdev);
+	struct pci_dev *pci_dev = vp_dev->pci_dev;
+
+	if ((features & BIT_ULL(VIRTIO_F_SR_IOV)) &&
+			pci_find_ext_capability(pci_dev, PCI_EXT_CAP_ID_SRIOV))
+		__virtio_set_bit(vdev, VIRTIO_F_SR_IOV);
+}
+
 /* virtio config->finalize_features() implementation */
 static int vp_finalize_features(struct virtio_device *vdev)
 {
 	struct virtio_pci_device *vp_dev = to_vp_device(vdev);
+	u64 features = vdev->features;
 
 	/* Give virtio_ring a chance to accept features. */
 	vring_transport_features(vdev);
 
+	/* Give virtio_pci a chance to accept features. */
+	vp_transport_features(vdev, features);
+
 	if (!__virtio_test_bit(vdev, VIRTIO_F_VERSION_1)) {
 		dev_err(&vdev->dev, "virtio: device uses modern interface "
 			"but does not have VIRTIO_F_VERSION_1\n");