Code review comment for ~mfo/ubuntu/+source/xen:lp1956166

- we agreed to ignore the few days left for Impish
- patches LGTM, apply fine and have good headers to track where they are from
- One could argue it is a new feature, but by using zstd kernels we made this a bug that deserves to be fixed
- SRU template in the bug is ready
- it will grow a libzstd1 in focal, xen isn't in main anyway, but libzstd1 would be in any case :-)

The patches are quite huge, but that is what they are upstream.
You already went to some efforts reducing them - thanks.
You listed those references fine in the patch headers.

You already pre-built and pre-tested the changes.

Changelog is readable and complete and the bug reference is ok.
Double checked with debdiff that nothing else slipped in

Eventually it is up for the SRU team to decide, but this LGTM.
Sponsoring.