Merge branch 'xdp-ice-mbuf'

Maciej Fijalkowski says:

====================
Although this work started as an effort to add multi-buffer XDP support
to ice driver, as usual it turned out that some other side stuff needed
to be addressed, so let me give you an overview.

First patch adjusts legacy-rx in a way that it will be possible to refer
to skb_shared_info being at the end of the buffer when gathering up
frame fragments within xdp_buff.

Then, patches 2-9 prepare ice driver in a way that actual multi-buffer
patches will be easier to swallow.

10 and 11 are the meat. What is worth mentioning is that this set
actually *fixes* things as patch 11 removes the logic based on
next_dd/rs and we previously stepped away from this for ice_xmit_zc().
Currently, AF_XDP ZC XDP_TX workload is off as there are two cleaning
sides that can be triggered and two of them work on different internal
logic. This set unifies that and allows us to improve the performance by
2x with a trick on the last (13) patch.

12th is a simple cleanup of no longer fields from Tx ring.

I might be wrong but I have not seen anyone reporting performance impact
among patches that add XDP multi-buffer support to a particular driver.
Numbers below were gathered via xdp_rxq_info and xdp_redirect_map on
1500 MTU:

XDP_DROP      +1%
XDP_PASS      -1,2%
XDP_TX        -0,5%
XDP_REDIRECT  -3,3%

Cherry on top, which is not directly related to mbuf support (last
patch):

XDP_TX ZC +126%

Target the we agreed on was to not degrade performance for any action by
anything that would be over 5%, so our goal was met. Basically this set
keeps the performance where it was. Redirect is slower due to more
frequent tail bumps.
====================

Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Reviewed-by: Alexander Lobakin <alexandr.lobakin@intel.com>