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 muliple 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].
Sending this series as RFC as the winder closure is immenient. I plan on reposting as non-RFC once the tree re-opens, addressing any feedback I receive in the meantime.
Full outline on usage of the TX path is detailed in the documentation added in the first patch.
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.
2. Add netmem refcounting needed for the TX path.
3. Devmem TX netlink API.
4. Devmem TX net stack implementation.
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.c... [2] https://lore.kernel.org/netdev/20240913150913.1280238-2-sdf@fomichev.me/T/#m...
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
Mina Almasry (5): net: add devmem TCP TX documentation selftests: ncdevmem: Implement devmem TCP TX net: add get_netmem/put_netmem support net: devmem: Implement TX path net: devmem: make dmabuf unbinding scheduled work
Stanislav Fomichev (1): net: devmem: TCP tx netlink api
Documentation/netlink/specs/netdev.yaml | 12 + Documentation/networking/devmem.rst | 144 ++++++++- include/linux/skbuff.h | 15 +- include/linux/skbuff_ref.h | 4 +- include/net/netmem.h | 3 + include/net/sock.h | 1 + include/uapi/linux/netdev.h | 1 + include/uapi/linux/uio.h | 6 +- net/core/datagram.c | 41 ++- net/core/devmem.c | 110 ++++++- net/core/devmem.h | 70 ++++- net/core/netdev-genl-gen.c | 13 + net/core/netdev-genl-gen.h | 1 + net/core/netdev-genl.c | 67 ++++- net/core/skbuff.c | 36 ++- net/core/sock.c | 8 + net/ipv4/tcp.c | 36 ++- net/vmw_vsock/virtio_transport_common.c | 3 +- tools/include/uapi/linux/netdev.h | 1 + .../selftests/drivers/net/hw/ncdevmem.c | 276 +++++++++++++++++- 20 files changed, 802 insertions(+), 46 deletions(-)