introduce support for XDP programs in CPUMAP

Similar to what David Ahern proposed in [1] for DEVMAPs, introduce the capability to attach and run a XDP program to CPUMAP entries.
The idea behind this feature is to add the possibility to define on which CPU run the eBPF program if the underlying hw does not support RSS.
I respin patch 1/6 from a previous series sent by David [2].
The functionality has been tested on Marvell Espressobin, i40e and mlx5. Detailed tests results can be found here:
https://github.com/xdp-project/xdp-project/blob/master/areas/cpumap/cpumap04-map-xdp-prog.org

Changes since v6:
- rebase on top of bpf-next
- move bpf_cpumap_val and bpf_prog in the first bpf_cpu_map_entry cache-line

Changes since v5:
- move bpf_prog_put() in put_cpu_map_entry()
- remove READ_ONCE(rcpu->prog) in cpu_map_bpf_prog_run_xdp
- rely on bpf_prog_get_type() instead of bpf_prog_get_type_dev() in __cpu_map_load_bpf_program()

Changes since v4:
- move xdp_clear_return_frame_no_direct inside rcu section
- update David Ahern's email address

Changes since v3:
- fix typo in commit message
- fix access to ctx->ingress_ifindex in cpumap bpf selftest

Changes since v2:
- improved comments
- fix return value in xdp_convert_buff_to_frame
- added patch 1/9: "cpumap: use non-locked version __ptr_ring_consume_batched"
- do not run kmem_cache_alloc_bulk if all frames have been consumed by the XDP program attached to the CPUMAP entry
- removed bpf_trace_printk in kselftest

Changes since v1:
- added performance test results
- added kselftest support
- fixed memory accounting with page_pool
- extended xdp_redirect_cpu_user.c to load an external program to perform redirect
- reported ifindex to attached eBPF program
- moved bpf_cpumap_val definition to include/uapi/linux/bpf.h

[1] https://patchwork.ozlabs.org/project/netdev/cover/[email protected]/
[2] https://patchwork.ozlabs.org/project/netdev/patch/[email protected]/

David Ahern (1):
net: refactor xdp_convert_buff_to_frame

Jesper Dangaard Brouer (1):
cpumap: use non-locked version __ptr_ring_consume_batched

Lorenzo Bianconi (7):
samples/bpf: xdp_redirect_cpu_user: do not update bpf maps in option
loop
cpumap: formalize map value as a named struct
bpf: cpumap: add the possibility to attach an eBPF program to cpumap
bpf: cpumap: implement XDP_REDIRECT for eBPF programs attached to map
entries
libbpf: add SEC name for xdp programs attached to CPUMAP samples/bpf: xdp_redirect_cpu: load a eBPF program on cpumap
selftest: add tests for XDP programs in CPUMAP entries

 include/linux/bpf.h                           |   6 +
 include/net/xdp.h                             |  41 ++--
 include/trace/events/xdp.h                    |  16 +-
 include/uapi/linux/bpf.h                      |  14 ++
 kernel/bpf/cpumap.c                           | 162 +++++++++++---
 net/core/dev.c                                |   9 +
 samples/bpf/xdp_redirect_cpu_kern.c           |  25 ++-
 samples/bpf/xdp_redirect_cpu_user.c           | 209 ++++++++++++++++--
 tools/include/uapi/linux/bpf.h                |  14 ++
 tools/lib/bpf/libbpf.c                        |   2 +
 .../bpf/prog_tests/xdp_cpumap_attach.c        |  70 ++++++
 .../bpf/progs/test_xdp_with_cpumap_helpers.c  |  36 +++
 12 files changed, 531 insertions(+), 73 deletions(-)
 create mode 100644 tools/testing/selftests/bpf/prog_tests/xdp_cpumap_attach.c
 create mode 100644 tools/testing/selftests/bpf/progs/test_xdp_with_cpumap_helpers.c

2.26.2