net: ethtool: add support for symmetric-xor RSS hash

Symmetric RSS hash functions are beneficial in applications that monitor
both Tx and Rx packets of the same flow (IDS, software firewalls, ..etc).
Getting all traffic of the same flow on the same RX queue results in
higher CPU cache efficiency.

A NIC that supports "symmetric-xor" can achieve this RSS hash symmetry
by XORing the source and destination fields and pass the values to the
RSS hash algorithm.

The user may request RSS hash symmetry for a specific algorithm, via:

# ethtool -X eth0 hfunc <hash_alg> symmetric-xor

or turn symmetry off (asymmetric) by:

# ethtool -X eth0 hfunc <hash_alg>

The specific fields for each flow type should then be specified as usual
via:
# ethtool -N|-U eth0 rx-flow-hash <flow_type> s|d|f|n

Reviewed-by: Wojciech Drewek <wojciech.drewek@intel.com>
Signed-off-by: Ahmed Zaki <ahmed.zaki@intel.com>
Link: https://lore.kernel.org/r/20231213003321.605376-4-ahmed.zaki@intel.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

docs: networking: document multi-RSS context

There seems to be no docs for the concept of multiple RSS
contexts and how to configure it. I had to explain it three
times recently, the last one being the charm, document it.

Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Reviewed-by: Simon Horman <horms@kernel.org>
Reviewed-by: Edward Cree <ecree.xilinx@gmail.com>
Link: https://lore.kernel.org/r/20231018010758.2382742-1-kuba@kernel.org
Signed-off-by: Paolo Abeni <pabeni@redhat.com>

sock: Remove ->sendpage*() in favour of sendmsg(MSG_SPLICE_PAGES)

Remove ->sendpage() and ->sendpage_locked(). sendmsg() with
MSG_SPLICE_PAGES should be used instead. This allows multiple pages and
multipage folios to be passed through.

Signed-off-by: David Howells <dhowells@redhat.com>
Acked-by: Marc Kleine-Budde <mkl@pengutronix.de> # for net/can
cc: Jens Axboe <axboe@kernel.dk>
cc: Matthew Wilcox <willy@infradead.org>
cc: linux-afs@lists.infradead.org
cc: mptcp@lists.linux.dev
cc: rds-devel@oss.oracle.com
cc: tipc-discussion@lists.sourceforge.net
cc: virtualization@lists.linux-foundation.org
Link: https://lore.kernel.org/r/20230623225513.2732256-16-dhowells@redhat.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

docs: networking: update XPS to account for netif_set_xps_queue

With the introduction of netif_set_xps_queue, XPS can be enabled
by the driver at initialization.

Update the documentation to reflect this, as otherwise users
may incorrectly believe that the feature is off by default.

Fixes: 537c00de1c9b ("net: Add functions netif_reset_xps_queue and netif_set_xps_queue")
Signed-off-by: Willem de Bruijn <willemb@google.com>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

docs: add IRQ documentation at the core-api book

There are 4 IRQ documentation files under Documentation/*.txt.

Move them into a new directory (core-api/irq) and add a new
index file for it.

While here, use a title markup for the Debugging section of the
irq-domain.rst file.

Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>
Link: https://lore.kernel.org/r/2da7485c3718e1442e6b4c2dd66857b776e8899b.1588345503.git.mchehab+huawei@kernel.org
Signed-off-by: Jonathan Corbet <corbet@lwn.net>

doc: networking: integrate scaling document into doc tree

Convert scaling document into reStructuredText and add reference to
scaling document into main table of contents in network documentation.

There are no semantic changes.

There are no references to "scaling.txt" file. Whole kernel tree was
checked using:
$ grep -r "scaling\.txt"

Signed-off-by: Otto Sabart <ottosabart@seberm.com>
Signed-off-by: Jonathan Corbet <corbet@lwn.net>