linux-kernel - [RFC net-next v3 0/4] virtio

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Message-Id: <20250121191047.269844-1-jdamato@fastly.com>
Date: Tue, 21 Jan 2025 19:10:40 +0000
From: Joe Damato <jdamato@...tly.com>
To: netdev@...r.kernel.org
Cc: gerhard@...leder-embedded.com,
	jasowang@...hat.com,
	leiyang@...hat.com,
	xuanzhuo@...ux.alibaba.com,
	mkarsten@...terloo.ca,
	Joe Damato <jdamato@...tly.com>,
	Alexander Lobakin <aleksander.lobakin@...el.com>,
	Alexei Starovoitov <ast@...nel.org>,
	Andrew Lunn <andrew+netdev@...n.ch>,
	bpf@...r.kernel.org (open list:XDP (eXpress Data Path):Keyword:(?:\b|_)xdp(?:\b|_)),
	Daniel Borkmann <daniel@...earbox.net>,
	"David S. Miller" <davem@...emloft.net>,
	Eric Dumazet <edumazet@...gle.com>,
	Eugenio Pérez <eperezma@...hat.com>,
	Jakub Kicinski <kuba@...nel.org>,
	Jesper Dangaard Brouer <hawk@...nel.org>,
	John Fastabend <john.fastabend@...il.com>,
	Kuniyuki Iwashima <kuniyu@...zon.com>,
	linux-kernel@...r.kernel.org (open list),
	Lorenzo Bianconi <lorenzo@...nel.org>,
	"Michael S. Tsirkin" <mst@...hat.com>,
	Paolo Abeni <pabeni@...hat.com>,
	Sebastian Andrzej Siewior <bigeasy@...utronix.de>,
	Simon Horman <horms@...nel.org>,
	virtualization@...ts.linux.dev (open list:VIRTIO CORE AND NET DRIVERS)
Subject: [RFC net-next v3 0/4] virtio_net: Link queues to NAPIs

Greetings:

Welcome to RFC v3, since net-next is closed. See changelog below.

Recently [1], Jakub mentioned that there were a few drivers that are not
yet mapping queues to NAPIs.

While I don't have any of the other hardware mentioned, I do happen to
have a virtio_net laying around ;)

I've attempted to link queues to NAPIs, using the new locking Jakub
introduced avoiding RTNL.

Note: It seems virtio_net uses TX-only NAPIs which do not have NAPI IDs.
As such, I've left the TX NAPIs unset (as opposed to setting them to 0).

As per the discussion on the v2 [2], all RX queues now have their NAPIs
linked.

See the commit message of patch 3 for an example of how to get the NAPI
to queue mapping information.

See the commit message of patch 4 for an example of how NAPI IDs are
persistent despite queue count changes.

Thanks,
Joe

[1]: https://lore.kernel.org/netdev/20250109084301.2445a3e3@kernel.org/
[2]: https://lore.kernel.org/netdev/f8fe5618-af94-4f5b-8dbc-e8cae744aedf@engleder-embedded.com/

v3:
  - patch 3:
    - Removed the xdp checks completely, as Gerhard Engleder pointed
      out, they are likely not necessary.

  - patch 4:
    - Added Xuan Zhuo's Reviewed-by.

v2:
  - patch 1:
    - New in the v2 from Jakub.

  - patch 2:
    - Previously patch 1, unchanged from v1.
    - Added Gerhard Engleder's Reviewed-by.
    - Added Lei Yang's Tested-by.

  - patch 3:
    - Introduced virtnet_napi_disable to eliminate duplicated code
      in virtnet_xdp_set, virtnet_rx_pause, virtnet_disable_queue_pair,
      refill_work as suggested by Jason Wang.
    - As a result of the above refactor, dropped Reviewed-by and
      Tested-by from patch 3.

  - patch 4:
    - New in v2. Adds persistent NAPI configuration. See commit message
      for more details.

Jakub Kicinski (1):
  net: protect queue -> napi linking with netdev_lock()

Joe Damato (3):
  virtio_net: Prepare for NAPI to queue mapping
  virtio_net: Map NAPIs to queues
  virtio_net: Use persistent NAPI config

 drivers/net/virtio_net.c      | 38 +++++++++++++++++++++++++++--------
 include/linux/netdevice.h     |  9 +++++++--
 include/net/netdev_rx_queue.h |  2 +-
 net/core/dev.c                | 16 ++++++++++++---
 4 files changed, 51 insertions(+), 14 deletions(-)


base-commit: cf33d96f50903214226b379b3f10d1f262dae018
-- 
2.25.1