[ovs-git] [openvswitch/ovs] e8f563: netdev-afxdp: Best-effort configuration of XDP mode.

[Ilya Maximets]

  Branch: refs/heads/master
  Home:   https://github.com/openvswitch/ovs
  Commit: e8f5634484e8c9c77d389a25b6f38d4abeb435b5
      https://github.com/openvswitch/ovs/commit/e8f5634484e8c9c77d389a25b6f38d4abeb435b5
  Author: Ilya Maximets <i.maximets at ovn.org>
  Date:   2019-11-20 (Wed, 20 Nov 2019)

  Changed paths:
    M Documentation/intro/install/afxdp.rst
    M NEWS
    M lib/netdev-afxdp.c
    M lib/netdev-afxdp.h
    M lib/netdev-linux-private.h
    M tests/system-afxdp-macros.at
    M vswitchd/vswitch.xml

  Log Message:
  -----------
  netdev-afxdp: Best-effort configuration of XDP mode.

Until now there was only two options for XDP mode in OVS: SKB or DRV.
i.e. 'generic XDP' or 'native XDP with zero-copy enabled'.

Devices like 'veth' interfaces in Linux supports native XDP, but
doesn't support zero-copy mode.  This case can not be covered by
existing API and we have to use slower generic XDP for such devices.
There are few more issues, e.g. TCP is not supported in generic XDP
mode for veth interfaces due to kernel limitations, however it is
supported in native mode.

This change introduces ability to use native XDP without zero-copy
along with best-effort configuration option that enabled by default.
In best-effort case OVS will sequentially try different modes starting
from the fastest one and will choose the first acceptable for current
interface.  This will guarantee the best possible performance.

If user will want to choose specific mode, it's still possible by
setting the 'options:xdp-mode'.

This change additionally changes the API by renaming the configuration
knob from 'xdpmode' to 'xdp-mode' and also renaming the modes
themselves to be more user-friendly.

The full list of currently supported modes:
  * native-with-zerocopy - former DRV
  * native               - new one, DRV without zero-copy
  * generic              - former SKB
  * best-effort          - new one, chooses the best available from
                           3 above modes

Since 'best-effort' is a default mode, users will not need to
explicitely set 'xdp-mode' in most cases.

TCP related tests enabled back in system afxdp testsuite, because
'best-effort' will choose 'native' mode for veth interfaces
and this mode has no issues with TCP.

Signed-off-by: Ilya Maximets <i.maximets at ovn.org>
Acked-by: William Tu <u9012063 at gmail.com>
Acked-by: Eelco Chaudron <echaudro at redhat.com>