Re: [PATCH net-next v6 0/8] Device memory TCP TX

[Lei Yang <leiyang@redhat.com>]

I re-tested this series of patches v6 with virtio-net regression
tests, everything works fine.

Tested-by: Lei Yang <leiyang@redhat.com>

On Thu, Feb 27, 2025 at 12:13 PM Mina Almasry <almasrymina@google.com> wrote:
>
> v6: https://lore.kernel.org/netdev/20250222191517.743530-1-almasrymina@google.com/
> ===
>
> v6 has no major changes. Addressed a few issues from Paolo and David,
> and collected Acks from Stan. Thank you everyone for the review!
>
> Changes:
> - retain behavior to process MSG_FASTOPEN even if the provided cmsg is
>   invalid (Paolo).
> - Rework the freeing of tx_vec slightly (it now has its own err label).
>   (Paolo).
> - Squash the commit that makes dmabuf unbinding scheduled work into the
>   same one which implements the TX path so we don't run into future
>   errors on bisecting (Paolo).
> - Fix/add comments to explain how dmabuf binding refcounting works
>   (David).
>
> v5: https://lore.kernel.org/netdev/20250220020914.895431-1-almasrymina@google.com/
> ===
>
> v5 has no major changes; it clears up the relatively minor issues
> pointed out to in v4, and rebases the series on top of net-next to
> resolve the conflict with a patch that raced to the tree. It also
> collects the review tags from v4.
>
> Changes:
> - Rebase to net-next
> - Fix issues in selftest (Stan).
> - Address comments in the devmem and netmem driver docs (Stan and Bagas)
> - Fix zerocopy_fill_skb_from_devmem return error code (Stan).
>
> v4: https://lore.kernel.org/netdev/20250203223916.1064540-1-almasrymina@google.com/
> ===
>
> v4 mainly addresses the critical driver support issue surfaced in v3 by
> Paolo and Stan. Drivers aiming to support netmem_tx should make sure not
> to pass the netmem dma-addrs to the dma-mapping APIs, as these dma-addrs
> may come from dma-bufs.
>
> Additionally other feedback from v3 is addressed.
>
> Major changes:
> - Add helpers to handle netmem dma-addrs. Add GVE support for
>   netmem_tx.
> - Fix binding->tx_vec not being freed on error paths during the
>   tx binding.
> - Add a minimal devmem_tx test to devmem.py.
> - Clean up everything obsolete from the cover letter (Paolo).
>
> v3: https://patchwork.kernel.org/project/netdevbpf/list/?series=929401&state=*
> ===
>
> Address minor comments from RFCv2 and fix a few build warnings and
> ynl-regen issues. No major changes.
>
> RFC v2: https://patchwork.kernel.org/project/netdevbpf/list/?series=920056&state=*
> =======
>
> RFC v2 addresses much of the feedback from RFC v1. I plan on sending
> something close to this as net-next  reopens, sending it slightly early
> to get feedback if any.
>
> Major changes:
> --------------
>
> - much improved UAPI as suggested by Stan. We now interpret the iov_base
>   of the passed in iov from userspace as the offset into the dmabuf to
>   send from. This removes the need to set iov.iov_base = NULL which may
>   be confusing to users, and enables us to send multiple iovs in the
>   same sendmsg() call. ncdevmem and the docs show a sample use of that.
>
> - Removed the duplicate dmabuf iov_iter in binding->iov_iter. I think
>   this is good improvment as it was confusing to keep track of
>   2 iterators for the same sendmsg, and mistracking both iterators
>   caused a couple of bugs reported in the last iteration that are now
>   resolved with this streamlining.
>
> - Improved test coverage in ncdevmem. Now multiple sendmsg() are tested,
>   and sending multiple iovs in the same sendmsg() is tested.
>
> - Fixed issue where dmabuf unmapping was happening in invalid context
>   (Stan).
>
> ====================================================================
>
> The TX path had been dropped from the Device Memory TCP patch series
> post RFCv1 [1], to make that series slightly easier to review. This
> series rebases the implementation of the TX path on top of the
> net_iov/netmem framework agreed upon and merged. The motivation for
> the feature is thoroughly described in the docs & cover letter of the
> original proposal, so I don't repeat the lengthy descriptions here, but
> they are available in [1].
>
> Full outline on usage of the TX path is detailed in the documentation
> included with this series.
>
> Test example is available via the kselftest included in the series as well.
>
> The series is relatively small, as the TX path for this feature largely
> piggybacks on the existing MSG_ZEROCOPY implementation.
>
> Patch Overview:
> ---------------
>
> 1. Documentation & tests to give high level overview of the feature
>    being added.
>
> 1. Add netmem refcounting needed for the TX path.
>
> 2. Devmem TX netlink API.
>
> 3. Devmem TX net stack implementation.
>
> 4. Make dma-buf unbinding scheduled work to handle TX cases where it gets
>    freed from contexts where we can't sleep.
>
> 5. Add devmem TX documentation.
>
> 6. Add scaffolding enabling driver support for netmem_tx. Add helpers, driver
> feature flag, and docs to enable drivers to declare netmem_tx support.
>
> 7. Guard netmem_tx against being enabled against drivers that don't
>    support it.
>
> 8. Add devmem_tx selftests. Add TX path to ncdevmem and add a test to
>    devmem.py.
>
> Testing:
> --------
>
> Testing is very similar to devmem TCP RX path. The ncdevmem test used
> for the RX path is now augemented with client functionality to test TX
> path.
>
> * Test Setup:
>
> Kernel: net-next with this RFC and memory provider API cherry-picked
> locally.
>
> Hardware: Google Cloud A3 VMs.
>
> NIC: GVE with header split & RSS & flow steering support.
>
> Performance results are not included with this version, unfortunately.
> I'm having issues running the dma-buf exporter driver against the
> upstream kernel on my test setup. The issues are specific to that
> dma-buf exporter and do not affect this patch series. I plan to follow
> up this series with perf fixes if the tests point to issues once they're
> up and running.
>
> Special thanks to Stan who took a stab at rebasing the TX implementation
> on top of the netmem/net_iov framework merged. Parts of his proposal [2]
> that are reused as-is are forked off into their own patches to give full
> credit.
>
> [1] https://lore.kernel.org/netdev/20240909054318.1809580-1-almasrymina@google.com/
> [2] https://lore.kernel.org/netdev/20240913150913.1280238-2-sdf@fomichev.me/T/#m066dd407fbed108828e2c40ae50e3f4376ef57fd
>
> Cc: sdf@fomichev.me
> Cc: asml.silence@gmail.com
> Cc: dw@davidwei.uk
> Cc: Jamal Hadi Salim <jhs@mojatatu.com>
> Cc: Victor Nogueira <victor@mojatatu.com>
> Cc: Pedro Tammela <pctammela@mojatatu.com>
> Cc: Samiullah Khawaja <skhawaja@google.com>
>
>
> Mina Almasry (7):
>   net: add get_netmem/put_netmem support
>   net: devmem: Implement TX path
>   net: add devmem TCP TX documentation
>   net: enable driver support for netmem TX
>   gve: add netmem TX support to GVE DQO-RDA mode
>   net: check for driver support in netmem TX
>   selftests: ncdevmem: Implement devmem TCP TX
>
> Stanislav Fomichev (1):
>   net: devmem: TCP tx netlink api
>
>  Documentation/netlink/specs/netdev.yaml       |  12 +
>  Documentation/networking/devmem.rst           | 150 ++++++++-
>  .../networking/net_cachelines/net_device.rst  |   1 +
>  Documentation/networking/netdev-features.rst  |   5 +
>  Documentation/networking/netmem.rst           |  23 +-
>  drivers/net/ethernet/google/gve/gve_main.c    |   4 +
>  drivers/net/ethernet/google/gve/gve_tx_dqo.c  |   8 +-
>  include/linux/netdevice.h                     |   2 +
>  include/linux/skbuff.h                        |  17 +-
>  include/linux/skbuff_ref.h                    |   4 +-
>  include/net/netmem.h                          |  23 ++
>  include/net/sock.h                            |   1 +
>  include/uapi/linux/netdev.h                   |   1 +
>  net/core/datagram.c                           |  48 ++-
>  net/core/dev.c                                |   3 +
>  net/core/devmem.c                             | 115 ++++++-
>  net/core/devmem.h                             |  77 ++++-
>  net/core/netdev-genl-gen.c                    |  13 +
>  net/core/netdev-genl-gen.h                    |   1 +
>  net/core/netdev-genl.c                        |  73 ++++-
>  net/core/skbuff.c                             |  48 ++-
>  net/core/sock.c                               |   6 +
>  net/ipv4/ip_output.c                          |   3 +-
>  net/ipv4/tcp.c                                |  50 ++-
>  net/ipv6/ip6_output.c                         |   3 +-
>  net/vmw_vsock/virtio_transport_common.c       |   5 +-
>  tools/include/uapi/linux/netdev.h             |   1 +
>  .../selftests/drivers/net/hw/devmem.py        |  26 +-
>  .../selftests/drivers/net/hw/ncdevmem.c       | 300 +++++++++++++++++-
>  29 files changed, 950 insertions(+), 73 deletions(-)
>
>
> base-commit: 80c4a0015ce249cf0917a04dbb3cc652a6811079
> --
> 2.48.1.658.g4767266eb4-goog
>
>