[PATCH 0/7] Add vhost-net kernel support to pasta

[aerosouund <aerosound161@gmail.com>]

This work is based on the original v2 RFC by Eugenio Perez:

Link:
https://archives.passt.top/passt-dev/20250709174748.3514693-1-eperezma@redhat.com/

It is the first finished patch series for vhost-kernel support after a
third RFC was submitted:

Link:
https://archives.passt.top/passt-dev/20260802132155.870796-1-aerosound161@gmail.com/

vhost-net is a kernel device that allows reading and writing packets to a
tap device using virtqueues instead of read(2), write(2), and their
vectored counterparts. Frames are handed over through a shared descriptor
ring, so several of them can be passed to the kernel at once rather than
issuing a syscall per frame.

The v3 RFC didn't yield any performance improvements because, to retain
correctness, sends between pasta and the vhost-kernel thread had to be
synchronous. This patch series fixes this problem through the changes
introduced in the last commit, titled:

"tap/tcp: Replace tcp_payload_used with a ring buffer style index"

The changes reliably yield a roughly 2x speedup on the TX path (container
to host).

Numbers were obtained through iperf3 with the following methodology and
results:

Pasta command:
./pasta -f --runas 0:0 --map-guest-addr 192.168.0.5 
--vhost-kernel on --config-net 2729785

Host:
iperf3 -s1J

Container:
iperf3 -c 192.168.0.5 -t 10 -P4 -l 1M -w 32M -i1

With --vhost-kernel on:

[SUM]   0.00-10.00  sec  1.36 GBytes  1.17 Gbits/sec  3643 sender
[SUM]   0.00-10.00  sec  1.16 GBytes   999 Mbits/sec        receiver

With --vhost-kernel off:

[SUM]   0.00-10.00  sec   700 MBytes   587 Mbits/sec  3556 sender
[SUM]   0.00-10.10  sec   495 MBytes   411 Mbits/sec        receiver

Ammar Yasser (7):
  tap: Move the tap_hdr file to a separate file
  conf: Add context fields, epoll types and --vhost-kernel flag to pasta
  virtio: Add the pasta vhost-net interface and implementation
  tap: Implement the pasta vhost-net from-guest path
  tap, tcp, udp: Prepare the to-guest path for vhost-net
  tap: Implement the pasta vhost-net to-guest path
  tap/tcp: Replace tcp_payload_used with a ring buffer style index

 Makefile     |   2 +-
 conf.c       |  19 +++
 epoll_type.h |   4 +
 passt.c      |   9 ++
 passt.h      |  79 ++++++++++-
 tap.c        | 364 ++++++++++++++++++++++++++++++++++++++++++++-------
 tap.h        |  47 ++-----
 tap_hdr.h    |  23 ++++
 tcp_buf.c    | 143 +++++++++++++++-----
 tcp_buf.h    |   4 +
 udp.c        |  41 ++++--
 udp.h        |   3 +
 util.c       |  12 ++
 util.h       |   2 +
 vhost.c      | 295 +++++++++++++++++++++++++++++++++++++++++
 vhost.h      |  79 +++++++++++
 16 files changed, 1002 insertions(+), 124 deletions(-)
 create mode 100644 tap_hdr.h
 create mode 100644 vhost.c
 create mode 100644 vhost.h

-- 
2.39.5 (Apple Git-154)