On 03/17, Leon Romanovsky wrote:

On Fri, Mar 14, 2025 at 01:51:33PM -0700, Stanislav Fomichev wrote:

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On 03/12, Leon Romanovsky wrote:

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On Wed, Mar 12, 2025 at 04:20:08PM +0200, Nikolay Aleksandrov wrote:

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On 3/12/25 1:29 PM, Leon Romanovsky wrote:

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On Wed, Mar 12, 2025 at 11:40:05AM +0200, Nikolay Aleksandrov wrote:

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On 3/8/25 8:46 PM, Leon Romanovsky wrote:

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On Fri, Mar 07, 2025 at 01:01:50AM +0200, Nikolay Aleksandrov wrote:

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Also we have the ephemeral PDC connections>> that come and go as

needed. There more such objects coming with more

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state, configuration and lifecycle management. That is why we added a
separate netlink family to cleanly manage them without trying to fit
a square peg in a round hole so to speak.

Yeah, I saw that you are planning to use netlink to manage objects,
which is very questionable. It is slow, unreliable, requires sockets,
needs more parsing logic e.t.c

To avoid all this overhead, RDMA uses netlink-like ioctl calls, which
fits better for object configurations.

Thanks

We'd definitely like to keep using netlink for control path object
management. Also please note we're talking about genetlink family. It is
fast and reliable enough for us, very easily extensible,
has a nice precise object definition with policies to enforce various
limitations, has extensive tooling (e.g. ynl), communication can be
monitored in realtime for debugging (e.g. nlmon), has a nice human
readable error reporting, gives the ability to easily dump large object
groups with filters applied, YAML family definitions and so on.
Having sockets or parsing are not issues.

Of course it is issue as netlink relies on Netlink sockets, which means
that you constantly move your configuration data instead of doing
standard to whole linux kernel pattern of allocating configuration
structs in user-space and just providing pointer to that through ioctl
call.

And you still call copy_from_user on that user-space pointer. So how
is it an improvement over netlink? netlink is just a flexible tlv,
if you don't like read/write calls, we can add netlink_ioctl with
a pointer to netlink message...

You need to built that netlink message, which you do by multiple copying
in the user space.

I understand your desire to see netdev patterns everywhere and agree
with the position that netlink is a perfect choice for dynamic configurations.
However I hold a position that it is not good fit to configure strictly dependent
hardware objects.

You already have TLB-based API in drivers/infiniband, there is no need
to invent new one.

Let's revisit this discussion later depending on where ultra eth stuff
lands. If it gets folded into ibv subsystem - keeping the same ibv
conventions makes sense. If not, not sure I understand your "multiple copying
in the user space" argument.