2016-01-19 16:12, Yuanhan Liu:

 int
 vtpci_init(struct rte_pci_device *dev, struct virtio_hw *hw)
 {
-       hw->vtpci_ops = &legacy_ops;
+       hw->dev = dev;
+
+       /*
+        * Try if we can succeed reading virtio pci caps, which exists
+        * only on modern pci device. If failed, we fallback to legacy
+        * virtio handling.
+        */
+       if (virtio_read_caps(dev, hw) == 0) {
+               PMD_INIT_LOG(INFO, "modern virtio pci detected.");
+               hw->vtpci_ops = &modern_ops;
+               hw->modern    = 1;
+               dev->driver->drv_flags |= RTE_PCI_DRV_INTR_LSC;
+               return 0;
+       }

RTE_PCI_DRV_INTR_LSC is already set by virtio_resource_init_by_uio().
Do you mean interrupt was not supported with legacy virtio?