Comment 0 for bug 1836635

[Impact]

 * Support for Solarflare X2542 network adapter
   (Medford2 / SFC9250) in the sfc driver.

 * This network adapter is present on recent hardware,
   at least HP 2019 and Dell PowerEdge R740xd systems.

 * On recent-hardware deployments that would rather use
   the Bionic LTS / GA supported kernel and cannot move
   to HWE kernels this adapter is non functional at all.

[Test Case]

 * The X2542 adapter has been exercised with iperf3 and nc
   across 2 hosts on 25G link speed w/ MTUs 1400/1500/9000
   on both directions, for 1 week.

   Its performance is on par with the Cosmic 4.18 kernel
   (which contains all these patches) and the out-of-tree
   driver from the vendor.

 * The 7000 series adapter (for regression testing an old model,
   supported previously) has been exercised with iperf and netperf
   (TCP_STREAM, UDP_STREAM, TCP_RR, UDP_RR, and TCP_CRR) in one
   host (client/server in different adapter ports isolated with
   network namespaces, so traffic goes through the network switch),
   on 10G link speed on MTUs 1500/9000, for 1 weekend.

   No regressions observed between the original and test kernels.

[Regression Potential]

 * The patchset touches a lot of the sfc driver, so the potential
   for regression definitely exists. It has been tested on other
   adapter which uses the old code, and no regressions were found.