[dpdk-dev] secondary processes and private data

[Alejandro Lucero <alejandro.lucero@netronome.com>]

I've a problem when part of device private data needs to be private per
process.

Current multiprocess support shares device private data between primary and
secondaries but it is all dependent on a pointer initialized to the same
memory address by the multiprocess support code. If there is a per-process
data, If a secondary process changes it the primary gets affected, and the
same for additional secondaries which will affect not just the primary but
other previous secondaries.

The solution is to add support for this inside struct rte_eth_dev,
something like

void *secondary_priv_data;

so it is up to the secondaries to use this field if necessary.

NFP PMD creates the required rte_eth_devs specifically, similar to what is
done inside rte_ethdev.c but adding initialization for an interface needed
when calling device ethdev_init function. There are other PMDs doing this
but none has this requirement for per-process private data.

Please, let me know what you think about this change to struct rte_ethdev
or if you have a better idea for solving this problem.

Thanks