vfio-pci: Fix multifunction=on

When an assigned device is initialized it copies the device config
space into the emulated config space.  Unfortunately multifunction is
setup prior to the device initfn and gets clobbered.  We need to
restore it just like pci-assign does.

Signed-off-by: Alex Williamson <alex.williamson@redhat.com>
Reviewed-by: Bandan Das <bsd@redhat.com>
Message-id: 20131112185059.7262.33780.stgit@bling.home
Cc: qemu-stable@nongnu.org
Signed-off-by: Anthony Liguori <aliguori@amazon.com>

hw/misc/vfio.c

@@ -3568,6 +3568,13 @@ static int vfio_initfn(PCIDevice *pdev)
     vdev->emulated_config_bits[PCI_HEADER_TYPE] =
                                               PCI_HEADER_TYPE_MULTI_FUNCTION;
 
+    /* Restore or clear multifunction, this is always controlled by QEMU */
+    if (vdev->pdev.cap_present & QEMU_PCI_CAP_MULTIFUNCTION) {
+        vdev->pdev.config[PCI_HEADER_TYPE] |= PCI_HEADER_TYPE_MULTI_FUNCTION;
+    } else {
+        vdev->pdev.config[PCI_HEADER_TYPE] &= ~PCI_HEADER_TYPE_MULTI_FUNCTION;
+    }
+
     /*
      * Clear host resource mapping info.  If we choose not to register a
      * BAR, such as might be the case with the option ROM, we can get