v4: https://lore.kernel.org/netdev/20250203223916.1064540-1-almasrymina@google.c... ===
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.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 Cc: Samiullah Khawaja skhawaja@google.com
Mina Almasry (8): net: add get_netmem/put_netmem support net: devmem: Implement TX path net: devmem: make dmabuf unbinding scheduled work 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 | 14 +- 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 | 114 ++++++- net/core/devmem.h | 69 +++- 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 | 46 ++- 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 | 28 +- .../selftests/drivers/net/hw/ncdevmem.c | 300 +++++++++++++++++- 29 files changed, 931 insertions(+), 72 deletions(-)