On Tue, Nov 3, 2020 at 11:02 AM Jason Wang <jasow...@redhat.com> wrote:
> > On 2020/11/3 上午2:51, Andrew Melnychenko wrote: > > 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 > > > Yes, and it could also a lacking of CAP_BPF. > > > > * Live migration to the kernel that doesn't have eBPF support > > > Is there anything that we needs special treatment here? > > Possible case: rss=on, vhost=on, source system with kernel 5.8 (everything works) -> dest. system 5.6 (bpf does not work), the adapter functions, but all the steering does not use proper queues. > > > * Integration with current QEMU build > > > Yes, a question here: > > 1) Any reason for not using libbpf, e.g it has been shipped with some > distros > We intentionally do not use libbpf, as it present only on some distros. We can switch to libbpf, but this will disable bpf if libbpf is not installed > 2) It would be better if we can avoid shipping bytecodes > This creates new dependencies: llvm + clang + ... We would prefer byte code and ability to generate it if prerequisites are installed. > > > > * Additional usage for eBPF for packet filtering > > > Another interesting topics in to implement mac/vlan filters. And in the > future, I plan to add mac based steering. All of these could be done via > eBPF. > > No problem, we can cooperate if needed > > > > > Know issues: > > * hash population not supported by eBPF RSS: 'software' RSS used > > > Is this because there's not way to write to vnet header in STERRING BPF? > > Yes. We plan to submit changes for kernel to cooperate with BPF and populate the hash, this work is in progress > > > 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. > > > Are there any blocker for this? > No, can be added in v2 > > Just some quick questions after a glance of the codes. Will go through > them tomorrow. > > Thanks > > > > > > 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 > > > >
