On Wed, 29 Mar 2017 23:48:51 +0300
"Michael S. Tsirkin" [off-list ref] wrote:

Allows maintaining extra context per vq.  For ease of use, passing in
NULL is legal and disables the feature for all vqs.

Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
---
 drivers/misc/mic/vop/vop_main.c    |  9 ++++++---
 drivers/s390/virtio/kvm_virtio.c   |  6 ++++--
 drivers/s390/virtio/virtio_ccw.c   |  7 ++++---
 drivers/virtio/virtio_mmio.c       |  8 +++++---
 drivers/virtio/virtio_pci_common.c | 18 +++++++++++-------
 drivers/virtio/virtio_pci_common.h |  4 +++-
 drivers/virtio/virtio_pci_legacy.c |  4 +++-
 drivers/virtio/virtio_pci_modern.c | 12 ++++++++----
 drivers/virtio/virtio_ring.c       |  7 +++++--
 include/linux/virtio_config.h      | 18 +++++++++++++++---
 include/linux/virtio_ring.h        |  3 +++
 11 files changed, 67 insertions(+), 29 deletions(-)

This series really needs a cover letter, explaining the motivation for
adding this context.

From what I understand, you want to track some length parameter in
virtio-net. As you don't use indirect descriptors in that case, you
want to use a context instead. Did I get this correctly?