On Mon,  4 Jan 2016 01:56:09 +0800
Huawei Xie [off-list ref] wrote:

v2 changes:
 Remove unnecessary assignment of NULL to dev->data->mac_addrs
 Ajust one comment's position
 change LOG level from ERR to INFO

virtio PMD doesn't set RTE_PCI_DRV_NEED_MAPPING in drv_flags of its
eth_driver. It will try igb_uio and PORT IO in turn to configure
virtio device. Even user in guest VM doesn't want to use virtio for
DPDK, virtio PMD will take over the device blindly.

The more serious problem is kernel driver is still manipulating the
device, which causes driver conflict.

This patch checks if there is any kernel driver manipulating the
virtio device before virtio PMD uses port IO to configure the device.

Huawei Xie (4):
  eal: make the comment more accurate
  eal: set kdrv to RTE_KDRV_NONE if kernel driver isn't manipulating the device.
  virtio: return 1 to tell the kernel we don't take over this device
  virtio: check if any kernel driver is manipulating the virtio device

 drivers/net/virtio/virtio_ethdev.c     | 16 ++++++++++++++--
 lib/librte_eal/common/eal_common_pci.c |  8 ++++----
 lib/librte_eal/linuxapp/eal/eal_pci.c  |  2 +-
 3 files changed, 19 insertions(+), 7 deletions(-)

Overall looks good, thanks for addressing this.

It would be good to note that VFIO no-IOMMU mode should work for this
as well.