[v4,0/4] virtio-net: disable delayed refill when pausing rx

Message

Bui Quang Minh April 17, 2025, 7:28 a.m. UTC

Hi everyone,

This series tries to fix a deadlock in virtio-net when binding/unbinding
XDP program, XDP socket or resizing the rx queue.

When pausing rx (e.g. set up xdp, xsk pool, rx resize), we call
napi_disable() on the receive queue's napi. In delayed refill_work, it
also calls napi_disable() on the receive queue's napi. When
napi_disable() is called on an already disabled napi, it will sleep in
napi_disable_locked while still holding the netdev_lock. As a result,
later napi_enable gets stuck too as it cannot acquire the netdev_lock.
This leads to refill_work and the pause-then-resume tx are stuck
altogether.

This scenario can be reproducible by binding a XDP socket to virtio-net
interface without setting up the fill ring. As a result, try_fill_recv
will fail until the fill ring is set up and refill_work is scheduled.

This fix adds virtnet_rx_(pause/resume)_all helpers and fixes up the
virtnet_rx_resume to disable future and cancel all inflights delayed
refill_work before calling napi_disable() to pause the rx.

Version 4 changes:
- Add force zerocopy mode to xdp_helper
- Make virtio_net selftest use force zerocopy mode
- Move virtio_net selftest to drivers/net/hw

Version 3 changes:
- Patch 1: refactor to avoid code duplication

Version 2 changes:
- Add selftest for deadlock scenario

Thanks,
Quang Minh.

Bui Quang Minh (4):
  virtio-net: disable delayed refill when pausing rx
  selftests: net: move xdp_helper to net/lib
  selftests: net: add flag to force zerocopy mode in xdp_helper
  selftests: net: add a virtio_net deadlock selftest

 drivers/net/virtio_net.c                      | 69 +++++++++++++++----
 tools/testing/selftests/drivers/net/Makefile  |  2 -
 .../testing/selftests/drivers/net/hw/Makefile |  1 +
 .../selftests/drivers/net/hw/virtio_net.py    | 65 +++++++++++++++++
 tools/testing/selftests/drivers/net/queues.py |  4 +-
 tools/testing/selftests/net/lib/.gitignore    |  1 +
 tools/testing/selftests/net/lib/Makefile      |  1 +
 .../{drivers/net => net/lib}/xdp_helper.c     | 13 +++-
 8 files changed, 138 insertions(+), 18 deletions(-)
 create mode 100755 tools/testing/selftests/drivers/net/hw/virtio_net.py
 rename tools/testing/selftests/{drivers/net => net/lib}/xdp_helper.c (90%)