[RFC PATCH 0/6] eBPF RSS support for virtio-net

[Andrew Melnychenko]

Basic idea is to use eBPF to calculate and steer packets in TAP.
RSS(Receive Side Scaling) is used to distribute network packets to guest 
virtqueues
by calculating packet hash.
eBPF RSS allows us to use RSS with vhost TAP.

This set of patches introduces the usage of eBPF for packet steering
and RSS hash calculation:
* RSS(Receive Side Scaling) is used to distribute network packets to
guest virtqueues by calculating packet hash
* eBPF RSS suppose to be faster than already existing 'software'
implementation in QEMU
* Additionally adding support for the usage of RSS with vhost

Supported kernels: 5.8+

Implementation notes:
Linux TAP TUNSETSTEERINGEBPF ioctl was used to set the eBPF program.
Added eBPF support to qemu directly through a system call, see the
bpf(2) for details.
The eBPF program is part of the qemu and presented as an array of bpf
instructions.
The program can be recompiled by provided Makefile.ebpf(need to adjust
'linuxhdrs'),
although it's not required to build QEMU with eBPF support.
Added changes to virtio-net and vhost, primary eBPF RSS is used.
'Software' RSS used in the case of hash population and as a fallback option.
For vhost, the hash population feature is not reported to the guest.

Please also see the documentation in PATCH 6/6.

I am sending those patches as RFC to initiate the discussions and get
feedback on the following points:
* Fallback when eBPF is not supported by the kernel
* Live migration to the kernel that doesn't have eBPF support
* Integration with current QEMU build
* Additional usage for eBPF for packet filtering

Know issues:
* hash population not supported by eBPF RSS: 'software' RSS used
as a fallback, also, hash population feature is not reported to guests
with vhost.
* big-endian BPF support: for now, eBPF is disabled for big-endian systems.

Andrew (6):
  Added SetSteeringEBPF method for NetClientState.
  ebpf: Added basic eBPF API.
  ebpf: Added eBPF RSS program.
  ebpf: Added eBPF RSS loader.
  virtio-net: Added eBPF RSS to virtio-net.
  docs: Added eBPF documentation.

 MAINTAINERS                    |   6 +
 configure                      |  36 +++
 docs/ebpf.rst                  |  29 ++
 docs/ebpf_rss.rst              | 129 ++++++++
 ebpf/EbpfElf_to_C.py           |  67 ++++
 ebpf/Makefile.ebpf             |  38 +++
 ebpf/ebpf-stub.c               |  28 ++
 ebpf/ebpf.c                    | 107 +++++++
 ebpf/ebpf.h                    |  35 +++
 ebpf/ebpf_rss.c                | 178 +++++++++++
 ebpf/ebpf_rss.h                |  30 ++
 ebpf/meson.build               |   1 +
 ebpf/rss.bpf.c                 | 470 ++++++++++++++++++++++++++++
 ebpf/trace-events              |   4 +
 ebpf/trace.h                   |   2 +
 ebpf/tun_rss_steering.h        | 556 +++++++++++++++++++++++++++++++++
 hw/net/vhost_net.c             |   2 +
 hw/net/virtio-net.c            | 120 ++++++-
 include/hw/virtio/virtio-net.h |   4 +
 include/net/net.h              |   2 +
 meson.build                    |   3 +
 net/tap-bsd.c                  |   5 +
 net/tap-linux.c                |  19 ++
 net/tap-solaris.c              |   5 +
 net/tap-stub.c                 |   5 +
 net/tap.c                      |   9 +
 net/tap_int.h                  |   1 +
 net/vhost-vdpa.c               |   2 +
 28 files changed, 1889 insertions(+), 4 deletions(-)
 create mode 100644 docs/ebpf.rst
 create mode 100644 docs/ebpf_rss.rst
 create mode 100644 ebpf/EbpfElf_to_C.py
 create mode 100755 ebpf/Makefile.ebpf
 create mode 100644 ebpf/ebpf-stub.c
 create mode 100644 ebpf/ebpf.c
 create mode 100644 ebpf/ebpf.h
 create mode 100644 ebpf/ebpf_rss.c
 create mode 100644 ebpf/ebpf_rss.h
 create mode 100644 ebpf/meson.build
 create mode 100644 ebpf/rss.bpf.c
 create mode 100644 ebpf/trace-events
 create mode 100644 ebpf/trace.h
 create mode 100644 ebpf/tun_rss_steering.h

-- 
2.28.0