A 'foreign' rule is one for which the net_dev is not the sfc netdevice
 or any of its representors.  The driver registers indirect flow blocks
 for tunnel netdevs so that it can offload decap rules.  For example:

    tc filter add dev vxlan0 parent ffff: protocol ipv4 flower \
        enc_src_ip 10.1.0.2 enc_dst_ip 10.1.0.1 \
        enc_key_id 1000 enc_dst_port 4789 \
        action tunnel_key unset \
        action mirred egress redirect dev $REPRESENTOR

When notified of a rule like this, register an encap match on the IP
 and dport tuple (creating an Outer Rule table entry) and insert an MAE
 action rule to perform the decapsulation and deliver to the representee.

Moved efx_tc_delete_rule() below efx_tc_flower_release_encap_match() to
 avoid the need for a forward declaration.
Signed-off-by: Edward Cree <ecree.xilinx@gmail.com>
Reviewed-by: Simon Horman <simon.horman@corigine.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

Add a hashtable to detect duplicate and conflicting matches.  If match
 is not a duplicate, call MAE functions to add/remove it from OR table.
Calling code not added yet, so mark the new functions as unused.
Signed-off-by: Edward Cree <ecree.xilinx@gmail.com>
Reviewed-by: Simon Horman <simon.horman@corigine.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

An encap match corresponds to an entry in the exact-match Outer Rule
 table; the lookup response includes the encap type (protocol) allowing
 the hardware to continue parsing into the inner headers.
Signed-off-by: Edward Cree <ecree.xilinx@gmail.com>
Reviewed-by: Simon Horman <simon.horman@corigine.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

Translate the fields from flow dissector into struct efx_tc_match.
In efx_tc_flower_replace(), reject filters that match on them, because
 only 'foreign' filters (i.e. those for which the ingress dev is not
 the sfc netdev or any of its representors, e.g. a tunnel netdev) can
 use them.
Signed-off-by: Edward Cree <ecree.xilinx@gmail.com>
Reviewed-by: Simon Horman <simon.horman@corigine.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

Extend the MAE caps check to validate that the hardware supports these
 outer-header matches where used by the driver.
Extend efx_mae_populate_match_criteria() to fill in the outer rule ID
 and VNI match fields.
Nothing yet populates these match fields, nor creates outer rules.
Signed-off-by: Edward Cree <ecree.xilinx@gmail.com>
Reviewed-by: Simon Horman <simon.horman@corigine.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

Includes an explanation of the lifetime of the 'cursor' action-set `act`.
Signed-off-by: Edward Cree <ecree.xilinx@gmail.com>
Reviewed-by: Simon Horman <simon.horman@corigine.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

Herbert Xu says:

====================
macvlan: Allow some packets to bypass broadcast queue

This patch series allows some packets to bypass the broadcast
queue on receive.  Currently all multicast packets are queued
on receive and then processed in a work queue.  This is to avoid
an unbounded amount of work occurring in the receive path, as
one broadcast packet could easily translate into 4,000 packets.

However, for multicast packets with just one receiver (possible
for IPv6 ND), this introduces unnecessary latency as the packet
will go to exactly one device.

This series allows such multicast packets to be processed inline.
It also adds a toggle which lets the admin control what threshold
to set between queueing and not queueing.  A follow-up patch for
iproute will be posted.
====================
Signed-off-by: David S. Miller <davem@davemloft.net>

Make the broadcast cutoff configurable through netlink.  Note
that macvlan is weird because there is no central device for
us to configure (the lowerdev could be anything).  So all the
options are duplicated over what could be thousands of child
devices.

IFLA_MACVLAN_BC_QUEUE_LEN took the approach of taking the maximum
of all child device settings.  This is unnecessary as we could
simply store the option in the port device and take the last
child device that gets updated as the value to use.
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
Signed-off-by: David S. Miller <davem@davemloft.net>

As it stands all broadcast and multicast packets are queued and
processed in a work queue.  This is so that we don't overwhelm
the receive softirq path by generating thousands of packets or
more (see commit 412ca155 "macvlan: Move broadcasts into a
work queue").

As such all multicast packets will be delayed, even if they will
be received by a single macvlan device.  As using a workqueue
is not free in terms of latency, we should avoid this where possible.

This patch adds a new filter to determine which addresses should
be delayed and which ones won't.  This is done using a crude
counter of how many times an address has been added to the macvlan
port (ha->synced).  For now if an address has been added more than
once, then it will be considered to be broadcast.  This could be
tuned further by making this threshold configurable.
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
Signed-off-by: David S. Miller <davem@davemloft.net>

Matthieu Baerts says:

====================
mptcp: a couple of cleanups and improvements

Patch 1 removes an unneeded address copy in subflow_syn_recv_sock().

Patch 2 simplifies subflow_syn_recv_sock() to postpone some actions and
to avoid a bunch of conditionals.

Patch 3 stops reporting limits that are not taken into account when the
userspace PM is used.

Patch 4 adds a new test to validate that the 'subflows' field reported
by the kernel is correct. Such info can be retrieved via Netlink (e.g.
with ss) or getsockopt(SOL_MPTCP, MPTCP_INFO).

---
Changes in v2:
- Patch 3/4's commit message has been updated to use the correct SHA
- Rebased on latest net-next
- Link to v1: https://lore.kernel.org/r/20230324-upstream-net-next-20230324-misc-features-v1-0-5a29154592bd@tessares.net
====================
Signed-off-by: Matthieu Baerts <matthieu.baerts@tessares.net>
Signed-off-by: David S. Miller <davem@davemloft.net>

This patch adds the mptcp_info fields tests in endpoint_tests(). Add a
new function chk_mptcp_info() to check the given number of the given
mptcp_info field.

Link: https://github.com/multipath-tcp/mptcp_net-next/issues/330Signed-off-by: Geliang Tang <geliang.tang@suse.com>
Reviewed-by: Matthieu Baerts <matthieu.baerts@tessares.net>
Signed-off-by: Matthieu Baerts <matthieu.baerts@tessares.net>
Signed-off-by: David S. Miller <davem@davemloft.net>

Only the in-kernel PM uses the number of address and subflow limits
allowed per connection.

It then makes more sense not to display such info when other PMs are
used not to confuse the userspace by showing limits not being used.

While at it, we can get rid of the "val" variable and add indentations
instead.

It would have been good to have done this modification directly in
commit 4d25247d ("mptcp: bypass in-kernel PM restrictions for non-kernel PMs")
but as we change a bit the behaviour, it is fine not to backport it to
stable.
Acked-by: Paolo Abeni <pabeni@redhat.com>
Signed-off-by: Matthieu Baerts <matthieu.baerts@tessares.net>
Signed-off-by: David S. Miller <davem@davemloft.net>

Postpone the msk cloning to the child process creation
so that we can avoid a bunch of conditionals.

Link: https://github.com/multipath-tcp/mptcp_net-next/issues/61Signed-off-by: Paolo Abeni <pabeni@redhat.com>
Reviewed-by: Matthieu Baerts <matthieu.baerts@tessares.net>
Signed-off-by: Matthieu Baerts <matthieu.baerts@tessares.net>
Signed-off-by: David S. Miller <davem@davemloft.net>

In the syn_recv fallback path, the msk is unused. We can skip
setting the socket address.
Signed-off-by: Paolo Abeni <pabeni@redhat.com>
Reviewed-by: Matthieu Baerts <matthieu.baerts@tessares.net>
Signed-off-by: Matthieu Baerts <matthieu.baerts@tessares.net>
Signed-off-by: David S. Miller <davem@davemloft.net>

Kuniyuki Iwashima says:

====================
ipv6: Random cleanup for in6addr_any.

The first patch removes in6addr_any alternatives and the second
removes redundant initialisation of a local variable.

Changes:
  v2: Use ipv6_addr_any() in patch 1. (David Ahern)

  v1: https://lore.kernel.org/netdev/20230322012204.33157-1-kuniyu@amazon.com/
====================
Signed-off-by: David S. Miller <davem@davemloft.net>

We'll call memset(&tmp, 0, sizeof(tmp)) later.
Signed-off-by: Kuniyuki Iwashima <kuniyu@amazon.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

Some code defines the IPv6 wildcard address as a local variable and
use it with memcmp() or ipv6_addr_equal().

Let's use in6addr_any and ipv6_addr_any() instead.
Signed-off-by: Kuniyuki Iwashima <kuniyu@amazon.com>
Reviewed-by: Mark Bloch <mbloch@nvidia.com>
Reviewed-by: David Ahern <dsahern@kernel.org>
Signed-off-by: David S. Miller <davem@davemloft.net>

Bobby Eshleman says:

====================
Add support for sockmap to vsock.

We're testing usage of vsock as a way to redirect guest-local UDS
requests to the host and this patch series greatly improves the
performance of such a setup.

Compared to copying packets via userspace, this improves throughput by
121% in basic testing.

Tested as follows.

Setup: guest unix dgram sender -> guest vsock redirector -> host vsock
       server
Threads: 1
Payload: 64k
No sockmap:
- 76.3 MB/s
- The guest vsock redirector was
  "socat VSOCK-CONNECT:2:1234 UNIX-RECV:/path/to/sock"
Using sockmap (this patch):
- 168.8 MB/s (+121%)
- The guest redirector was a simple sockmap echo server,
  redirecting unix ingress to vsock 2:1234 egress.
- Same sender and server programs

*Note: these numbers are from RFC v1

Only the virtio transport has been tested. The loopback transport was
used in writing bpf/selftests, but not thoroughly tested otherwise.

This series requires the skb patch.

Changes in v4:
- af_vsock: fix parameter alignment in vsock_dgram_recvmsg()
- af_vsock: add TCP_ESTABLISHED comment in vsock_dgram_connect()
- vsock/bpf: change ret type to bool

Changes in v3:
- vsock/bpf: Refactor wait logic in vsock_bpf_recvmsg() to avoid
  backwards goto
- vsock/bpf: Check psock before acquiring slock
- vsock/bpf: Return bool instead of int of 0 or 1
- vsock/bpf: Wrap macro args __sk/__psock in parens
- vsock/bpf: Place comment trailer */ on separate line

Changes in v2:
- vsock/bpf: rename vsock_dgram_* -> vsock_*
- vsock/bpf: change sk_psock_{get,put} and {lock,release}_sock() order
  to minimize slock hold time
- vsock/bpf: use "new style" wait
- vsock/bpf: fix bug in wait log
- vsock/bpf: add check that recvmsg sk_type is one dgram, seqpacket, or
  stream.  Return error if not one of the three.
- virtio/vsock: comment __skb_recv_datagram() usage
- virtio/vsock: do not init copied in read_skb()
- vsock/bpf: add ifdef guard around struct proto in dgram_recvmsg()
- selftests/bpf: add vsock loopback config for aarch64
- selftests/bpf: add vsock loopback config for s390x
- selftests/bpf: remove vsock device from vmtest.sh qemu machine
- selftests/bpf: remove CONFIG_VIRTIO_VSOCKETS=y from config.x86_64
- vsock/bpf: move transport-related (e.g., if (!vsk->transport)) checks
  out of fast path
====================
Signed-off-by: Bobby Eshleman <bobby.eshleman@bytedance.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

Add a test case testing the redirection from connectible AF_VSOCK
sockets to connectible AF_UNIX sockets.
Signed-off-by: Bobby Eshleman <bobby.eshleman@bytedance.com>
Acked-by: Stefano Garzarella <sgarzare@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

Add vsock loopback to the test kernel.

This allows sockmap for vsock to be tested.
Signed-off-by: Bobby Eshleman <bobby.eshleman@bytedance.com>
Acked-by: Stefano Garzarella <sgarzare@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

This patch adds sockmap support for vsock sockets. It is intended to be
usable by all transports, but only the virtio and loopback transports
are implemented.

SOCK_STREAM, SOCK_DGRAM, and SOCK_SEQPACKET are all supported.
Signed-off-by: Bobby Eshleman <bobby.eshleman@bytedance.com>
Acked-by: Michael S. Tsirkin <mst@redhat.com>
Reviewed-by: Stefano Garzarella <sgarzare@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

This adds the vsock_perf binary to the gitignore file.

Fixes: 8abbffd2 ("test/vsock: vsock_perf utility")
Signed-off-by: Bobby Eshleman <bobby.eshleman@bytedance.com>
Reviewed-by: Arseniy Krasnov <AVKrasnov@sberdevices.ru>
Reviewed-by: Stefano Garzarella <sgarzare@redhat.com>
Link: https://lore.kernel.org/r/20230327-vsock-add-vsock-perf-to-ignore-v1-1-f28a84f3606b@bytedance.comSigned-off-by: Jakub Kicinski <kuba@kernel.org>

Donald Hunter says:

====================
ynl: add support for user headers and struct attrs

Add support for user headers and struct attrs to YNL. This patchset adds
features to ynl and add a partial spec for openvswitch that demonstrates
use of the features.

Patch 1-4 add features to ynl
Patch 5 adds partial openvswitch specs that demonstrate the new features
Patch 6-7 add documentation for legacy structs and for sub-type
====================

Link: https://lore.kernel.org/r/20230327083138.96044-1-donald.hunter@gmail.comSigned-off-by: Jakub Kicinski <kuba@kernel.org>

Add a definition for sub-type to the protocol spec doc and a description of
its usage for C arrays in genetlink-legacy.
Signed-off-by: Donald Hunter <donald.hunter@gmail.com>
Reviewed-by: Bagas Sanjaya <bagasdotme@gmail.com>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

Describe the genetlink-legacy support for using struct definitions
for fixed headers and for binary attributes.
Signed-off-by: Donald Hunter <donald.hunter@gmail.com>
Reviewed-by: Bagas Sanjaya <bagasdotme@gmail.com>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

The openvswitch family has a fixed header, uses struct attrs and has array
values. This partial spec demonstrates these features in the YNL CLI. These
specs are sufficient to create, delete and dump datapaths and to dump vports:

$ ./tools/net/ynl/cli.py \
    --spec Documentation/netlink/specs/ovs_datapath.yaml \
    --do dp-new --json '{ "dp-ifindex": 0, "name": "demo", "upcall-pid": 0}'
None

$ ./tools/net/ynl/cli.py \
    --spec Documentation/netlink/specs/ovs_datapath.yaml \
    --dump dp-get --json '{ "dp-ifindex": 0 }'
[{'dp-ifindex': 3,
  'masks-cache-size': 256,
  'megaflow-stats': {'cache-hits': 0,
                     'mask-hit': 0,
                     'masks': 0,
                     'pad1': 0,
                     'padding': 0},
  'name': 'test',
  'stats': {'flows': 0, 'hit': 0, 'lost': 0, 'missed': 0},
  'user-features': {'dispatch-upcall-per-cpu',
                    'tc-recirc-sharing',
                    'unaligned'}},
 {'dp-ifindex': 48,
  'masks-cache-size': 256,
  'megaflow-stats': {'cache-hits': 0,
                     'mask-hit': 0,
                     'masks': 0,
                     'pad1': 0,
                     'padding': 0},
  'name': 'demo',
  'stats': {'flows': 0, 'hit': 0, 'lost': 0, 'missed': 0},
  'user-features': set()}]

$ ./tools/net/ynl/cli.py \
    --spec Documentation/netlink/specs/ovs_datapath.yaml \
    --do dp-del --json '{ "dp-ifindex": 0, "name": "demo"}'
None

$ ./tools/net/ynl/cli.py \
    --spec Documentation/netlink/specs/ovs_vport.yaml \
    --dump vport-get --json '{ "dp-ifindex": 3 }'
[{'dp-ifindex': 3,
  'ifindex': 3,
  'name': 'test',
  'port-no': 0,
  'stats': {'rx-bytes': 0,
            'rx-dropped': 0,
            'rx-errors': 0,
            'rx-packets': 0,
            'tx-bytes': 0,
            'tx-dropped': 0,
            'tx-errors': 0,
            'tx-packets': 0},
  'type': 'internal',
  'upcall-pid': [0],
  'upcall-stats': {'fail': 0, 'success': 0}}]
Signed-off-by: Donald Hunter <donald.hunter@gmail.com>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

Add support for netlink families that add an optional fixed header structure
after the genetlink header and before any attributes. The fixed-header can be
specified on a per op basis, or once for all operations, which serves as a
default value that can be overridden.
Signed-off-by: Donald Hunter <donald.hunter@gmail.com>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

Add support for decoding attributes that contain C structs.
Signed-off-by: Donald Hunter <donald.hunter@gmail.com>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

Add support for decoding C arrays from binay blobs in genetlink-legacy
messages.
Signed-off-by: Donald Hunter <donald.hunter@gmail.com>
Reviewed-by: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

Add python classes for struct definitions to nlspec
Signed-off-by: Donald Hunter <donald.hunter@gmail.com>
Reviewed-by: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

Saeed Mahameed says:

====================
mlx5-updates-2023-03-20

mlx5 dynamic msix

This patch series adds support for dynamic msix vectors allocation in mlx5.

Eli Cohen Says:

================

The following series of patches modifies mlx5_core to work with the
dynamic MSIX API. Currently, mlx5_core allocates all the interrupt
vectors it needs and distributes them amongst the consumers. With the
introduction of dynamic MSIX support, which allows for allocation of
interrupts more than once, we now allocate vectors as we need them.
This allows other drivers running on top of mlx5_core to allocate
interrupt vectors for their own use. An example for this is mlx5_vdpa,
which uses these vectors to propagate interrupts directly from the
hardware to the vCPU [1].

As a preparation for using this series, a use after free issue is fixed
in lib/cpu_rmap.c and the allocator for rmap entries has been modified.
A complementary API for irq_cpu_rmap_add() has also been introduced.

[1] https://git.kernel.org/pub/scm/linux/kernel/git/saeed/linux.git/patch/?id=0f2bf1fcae96a83b8c5581854713c9fc3407556e

================

* tag 'mlx5-updates-2023-03-20' of git://git.kernel.org/pub/scm/linux/kernel/git/saeed/linux:
  net/mlx5: Provide external API for allocating vectors
  net/mlx5: Use one completion vector if eth is disabled
  net/mlx5: Refactor calculation of required completion vectors
  net/mlx5: Move devlink registration before mlx5_load
  net/mlx5: Use dynamic msix vectors allocation
  net/mlx5: Refactor completion irq request/release code
  net/mlx5: Improve naming of pci function vectors
  net/mlx5: Use newer affinity descriptor
  net/mlx5: Modify struct mlx5_irq to use struct msi_map
  net/mlx5: Fix wrong comment
  net/mlx5e: Coding style fix, add empty line
  lib: cpu_rmap: Add irq_cpu_rmap_remove to complement irq_cpu_rmap_add
  lib: cpu_rmap: Use allocator for rmap entries
  lib: cpu_rmap: Avoid use after free on rmap->obj array entries
====================

Link: https://lore.kernel.org/r/20230324231341.29808-1-saeed@kernel.orgSigned-off-by: Jakub Kicinski <kuba@kernel.org>

We don't state explicitly that reverts need to be submitted
as a patch. It occasionally comes up.
Reviewed-by: Jacob Keller <jacob.e.keller@intel.com>
Reviewed-by: Florian Fainelli <f.fainelli@gmail.com>
Link: https://lore.kernel.org/r/20230327172646.2622943-1-kuba@kernel.orgSigned-off-by: Jakub Kicinski <kuba@kernel.org>

clang with W=1 reports
drivers/net/ethernet/8390/axnet_cs.c:653:9: error: variable
  'xfer_count' set but not used [-Werror,-Wunused-but-set-variable]
    int xfer_count = count;
        ^
This variable is not used so remove it.
Signed-off-by: Tom Rix <trix@redhat.com>
Reviewed-by: Simon Horman <simon.horman@corigine.com>
Link: https://lore.kernel.org/r/20230327235423.1777590-1-trix@redhat.comSigned-off-by: Jakub Kicinski <kuba@kernel.org>

This reverts commit ce1fdb06. It turned
out this actually introduces a race condition. netif_running() is not a
suitable check for get_stats.
Reported-by: Sergey Shtylyov <s.shtylyov@omp.ru>
Signed-off-by: Wolfram Sang <wsa+renesas@sang-engineering.com>
Reviewed-by: Sergey Shtylyov <s.shtylyov@omp.ru>
Reviewed-by: Simon Horman <simon.horman@corigine.com>
Link: https://lore.kernel.org/r/20230327152112.15635-1-wsa+renesas@sang-engineering.comSigned-off-by: Jakub Kicinski <kuba@kernel.org>

Thomas Gleixner says:

====================
net, refcount: Address dst_entry reference count scalability issues

This is version 3 of this series. Version 2 can be found here:

     https://lore.kernel.org/lkml/20230307125358.772287565@linutronix.de

Wangyang and Arjan reported a bottleneck in the networking code related to
struct dst_entry::__refcnt. Performance tanks massively when concurrency on
a dst_entry increases.

This happens when there are a large amount of connections to or from the
same IP address. The memtier benchmark when run on the same host as
memcached amplifies this massively. But even over real network connections
this issue can be observed at an obviously smaller scale (due to the
network bandwith limitations in my setup, i.e. 1Gb). How to reproduce:

  Run memcached with -t $N and memtier_benchmark with -t $M and --ratio=1:100
  on the same machine. localhost connections amplify the problem.

  Start with the defaults for $N and $M and increase them. Depending on
  your machine this will tank at some point. But even in reasonably small
  $N, $M scenarios the refcount operations and the resulting false sharing
  fallout becomes visible in perf top. At some point it becomes the
  dominating issue.

There are two factors which make this reference count a scalability issue:

   1) False sharing

      dst_entry:__refcnt is located at offset 64 of dst_entry, which puts
      it into a seperate cacheline vs. the read mostly members located at
      the beginning of the struct.

      That prevents false sharing vs. the struct members in the first 64
      bytes of the structure, but there is also

      	    dst_entry::lwtstate

      which is located after the reference count and in the same cache
      line. This member is read after a reference count has been acquired.

      The other problem is struct rtable, which embeds a struct dst_entry
      at offset 0. struct dst_entry has a size of 112 bytes, which means
      that the struct members of rtable which follow the dst member share
      the same cache line as dst_entry::__refcnt. Especially

      	  rtable::rt_genid

      is also read by the contexts which have a reference count acquired
      already.

      When dst_entry:__refcnt is incremented or decremented via an atomic
      operation these read accesses stall and contribute to the performance
      problem.

   2) atomic_inc_not_zero()

      A reference on dst_entry:__refcnt is acquired via
      atomic_inc_not_zero() and released via atomic_dec_return().

      atomic_inc_not_zero() is implemted via a atomic_try_cmpxchg() loop,
      which exposes O(N^2) behaviour under contention with N concurrent
      operations. Contention scalability is degrading with even a small
      amount of contenders and gets worse from there.

      Lightweight instrumentation exposed an average of 8!! retry loops per
      atomic_inc_not_zero() invocation in a inc()/dec() loop running
      concurrently on 112 CPUs.

      There is nothing which can be done to make atomic_inc_not_zero() more
      scalable.

The following series addresses these issues:

    1) Reorder and pad struct dst_entry to prevent the false sharing.

    2) Implement and use a reference count implementation which avoids the
       atomic_inc_not_zero() problem.

       It is slightly less performant in the case of the final 0 -> -1
       transition, but the deconstruction of these objects is a low
       frequency event. get()/put() pairs are in the hotpath and that's
       what this implementation optimizes for.

       The algorithm of this reference count is only suitable for RCU
       managed objects. Therefore it cannot replace the refcount_t
       algorithm, which is also based on atomic_inc_not_zero(), due to a
       subtle race condition related to the 0 -> -1 transition and the final
       verdict to mark the reference count dead. See details in patch 2/3.

       It might be just my lack of imagination which declares this to be
       impossible and I'd be happy to be proven wrong.

       As a bonus the new rcuref implementation provides underflow/overflow
       detection and mitigation while being performance wise on par with
       open coded atomic_inc_not_zero() / atomic_dec_return() pairs even in
       the non-contended case.

The combination of these two changes results in performance gains in micro
benchmarks and also localhost and networked memtier benchmarks talking to
memcached. It's hard to quantify the benchmark results as they depend
heavily on the micro-architecture and the number of concurrent operations.

The overall gain of both changes for localhost memtier ranges from 1.2X to
3.2X and from +2% to %5% range for networked operations on a 1Gb connection.

A micro benchmark which enforces maximized concurrency shows a gain between
1.2X and 4.7X!!!

Obviously this is focussed on a particular problem and therefore needs to
be discussed in detail. It also requires wider testing outside of the cases
which this is focussed on.

Though the false sharing issue is obvious and should be addressed
independent of the more focussed reference count changes.

The series is also available from git:

  git://git.kernel.org/pub/scm/linux/kernel/git/tglx/devel.git rcuref

Changes vs. V2:

  - Rename __refcnt to __rcuref (Linus)

  - Fix comments and changelogs (Mark, Qiuxu)

  - Fixup kernel doc of generated atomic_add_negative() variants

I want to say thanks to Wangyang who analyzed the issue and provided the
initial fix for the false sharing problem. Further thanks go to Arjan
Peter, Marc, Will and Borislav for valuable input and providing test
results on machines which I do not have access to, and to Linus and
Eric, Qiuxu and Mark for helpful feedback.
====================

Link: https://lore.kernel.org/r/20230323102649.764958589@linutronix.deSigned-off-by: Jakub Kicinski <kuba@kernel.org>

Under high contention dst_entry::__refcnt becomes a significant bottleneck.

atomic_inc_not_zero() is implemented with a cmpxchg() loop, which goes into
high retry rates on contention.

Switch the reference count to rcuref_t which results in a significant
performance gain. Rename the reference count member to __rcuref to reflect
the change.

The gain depends on the micro-architecture and the number of concurrent
operations and has been measured in the range of +25% to +130% with a
localhost memtier/memcached benchmark which amplifies the problem
massively.

Running the memtier/memcached benchmark over a real (1Gb) network
connection the conversion on top of the false sharing fix for struct
dst_entry::__refcnt results in a total gain in the 2%-5% range over the
upstream baseline.
Reported-by: Wangyang Guo <wangyang.guo@intel.com>
Reported-by: Arjan Van De Ven <arjan.van.de.ven@intel.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Link: https://lore.kernel.org/r/20230307125538.989175656@linutronix.de
Link: https://lore.kernel.org/r/20230323102800.215027837@linutronix.deSigned-off-by: Jakub Kicinski <kuba@kernel.org>

dst_entry::__refcnt is highly contended in scenarios where many connections
happen from and to the same IP. The reference count is an atomic_t, so the
reference count operations have to take the cache-line exclusive.

Aside of the unavoidable reference count contention there is another
significant problem which is caused by that: False sharing.

perf top identified two affected read accesses. dst_entry::lwtstate and
rtable::rt_genid.

dst_entry:__refcnt is located at offset 64 of dst_entry, which puts it into
a seperate cacheline vs. the read mostly members located at the beginning
of the struct.

That prevents false sharing vs. the struct members in the first 64
bytes of the structure, but there is also

  dst_entry::lwtstate

which is located after the reference count and in the same cache line. This
member is read after a reference count has been acquired.

struct rtable embeds a struct dst_entry at offset 0. struct dst_entry has a
size of 112 bytes, which means that the struct members of rtable which
follow the dst member share the same cache line as dst_entry::__refcnt.
Especially

  rtable::rt_genid

is also read by the contexts which have a reference count acquired
already.

When dst_entry:__refcnt is incremented or decremented via an atomic
operation these read accesses stall. This was found when analysing the
memtier benchmark in 1:100 mode, which amplifies the problem extremly.

Move the rt[6i]_uncached[_list] members out of struct rtable and struct
rt6_info into struct dst_entry to provide padding and move the lwtstate
member after that so it ends up in the same cache line.

The resulting improvement depends on the micro-architecture and the number
of CPUs. It ranges from +20% to +120% with a localhost memtier/memcached
benchmark.

[ tglx: Rearrange struct ]
Signed-off-by: Wangyang Guo <wangyang.guo@intel.com>
Signed-off-by: Arjan van de Ven <arjan@linux.intel.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Eric Dumazet <edumazet@google.com>
Reviewed-by: David Ahern <dsahern@kernel.org>
Link: https://lore.kernel.org/r/20230323102800.042297517@linutronix.deSigned-off-by: Jakub Kicinski <kuba@kernel.org>

Pulling rcurefs from Peter for tglx's work.

Link: https://lore.kernel.org/all/20230328084534.GE4253@hirez.programming.kicks-ass.net/Signed-off-by: Jakub Kicinski <kuba@kernel.org>

The cited commit caused the following build break in mlx5 due to a change
in size of MAX_SKB_FRAGS.

error: format '%lu' expects argument of type 'long unsigned int',
       but argument 7 has type 'unsigned int' [-Werror=format=]

Fix this by explicit casting.

Fixes: 3948b059 ("net: introduce a config option to tweak MAX_SKB_FRAGS")
Signed-off-by: Saeed Mahameed <saeedm@nvidia.com>
Link: https://lore.kernel.org/r/20230328200723.125122-1-saeed@kernel.orgSigned-off-by: Jakub Kicinski <kuba@kernel.org>

By default, the tagged ingress packets to the switch from the host port
P0 get internal switch priority assigned equal to the DMA CPPI channel
number they came from, unless CPSW_P0_CONTROL_REG.RX_REMAP_VLAN is enabled.
This causes issues with applying QoS policies and mapping packets on
external port fifos, because the default configuration is vlan_aware and
DMA CPPI channels are shared between all external ports.

Hence enable CPSW_P0_CONTROL_REG.RX_REMAP_VLAN so packet will preserve
internal switch priority assigned following the VLAN(priority) tag no
matter through which DMA CPPI Channels packets enter the switch.
Signed-off-by: Grygorii Strashko <grygorii.strashko@ti.com>
Signed-off-by: Siddharth Vadapalli <s-vadapalli@ti.com>
Link: https://lore.kernel.org/r/20230327092103.3256118-1-s-vadapalli@ti.comSigned-off-by: Paolo Abeni <pabeni@redhat.com>