[Qemu-stable] [PATCH 0/2] virtio-pci: Improve device plugging whith legacy backends

[Maxime Coquelin]

This series makes device plugging more robust, to avoid guest to be confused
when the backend doesn't support VIRTIO_F_VERSION_1.

The problem is seen with Linux guests running mainline kernels, when backend
doesn't support the feature:
virtio_net virtio0: virtio: device uses modern interface but does not have 
VIRTIO_F_VERSION_1.
When it happens, the modern device probe returns -EINVAL, whereas its caller
expects -ENODEV being returned to switch to legacy device probing.

We need to make QEMU more robust to ensure the guest won't be confused,
so this series exposes modern interface only when backend support it.

It has been tested with vhost-net and vhost-user backends in client
and server modes.

Maxime Coquelin (2):
  virtio: Add backend feature testing functionnality
  virtio-pci: Disable modern interface if backend without
    VIRTIO_F_VERSION_1

 hw/virtio/virtio-pci.c     | 15 +++++++++++++++
 hw/virtio/virtio-pci.h     |  5 +++++
 hw/virtio/virtio.c         | 14 ++++++++++++++
 include/hw/virtio/virtio.h |  2 ++
 4 files changed, 36 insertions(+)

-- 
2.7.4