Re: Query on new ethtool RSS hashing options

On Sat, Mar 06, 2021 at 14:54, Vladimir Oltean [off-list ref] wrote:

On Sat, Mar 06, 2021 at 05:38:14PM +0530, Sunil Kovvuri wrote:

quoted

quoted

Can you share the format of the DSA tag? Is there a driver for it
upstream? Do we need to represent it in union ethtool_flow_union?

No, there is no driver for this tag in the kernel.
I have attached the tag format.
There are multiple DSA tag formats and representing them ethtool_flow
union would be difficult.
Hence wondering if it would be okay to add a more flexible way ie
offset and num_bytes from the start of packet.

How sure are you that the tag format you've shared is not identical to
the one parsed by net/dsa/tag_dsa.c?

That is indeed the format parsed by tag_dsa.c. Based on the layout in
the image, I am pretty sure that it is from the functional spec. of the
Amethyst (6393X). So while the format is supported, that specific device
is not. Hopefully that will change soon:

https://lore.kernel.org/netdev/cover.1610071984.git.pavana.sharma@digi.com/ (local)

As for the NIC: Marvell has an EVK for the Amethyst, connected to a
CN9130 SoC. The ethernet controllers in those can parse DSA tags in
hardware, so I would put my money on that.

The upstream driver (mvpp2) does not seem to support it though, AFAIK.