Bug 2110203

+++ This bug was initially created as a clone of Bug #2107466 +++

Description of problem:
For zerocopy, we don't support zerocopy enabled when compress is on. 
But when we set migrate capabilities multifd, zerocopy, compress together, they can succeed;
when set these capability separately, zerocopy can't be enabled under compress enabled, it's the expectation


Version-Release number of selected component (if applicable):
hosts info: hosts info: kernel-5.14.0-121.el9.x86_64 & qemu-kvm-7.0.0-8.el9.x86_64
guest info: kernel-5.14.0-125.el9.x86_64


How reproducible:
100%


Steps to Reproduce:
1.Boot a guest
2.Set multifd, zerocopy, compress capabilities on together:
{"execute":"migrate-set-capabilities","arguments":{"capabilities":[{"capability":"xbzrle","state":false},{"capability":"auto-converge","state":false},{"capability":"rdma-pin-all","state":false},{"capability":"postcopy-ram","state":false},{"capability":"compress","state":true},{"capability":"pause-before-switchover","state":false},{"capability":"late-block-activate","state":false},{"capability":"multifd","state":true},{"capability":"dirty-bitmaps","state":false},{"capability":"return-path","state":false},{"capability":"zero-copy-send","state":true}]}}
{"return": {}}


Actual results:
Same as Steps, enable compress, multifd, zerocopy capabilities together succeed


Expected results:
Can't enable zerocopy and compress capabilities together

If we enable compress, multifd, zerocopy separately, zerocopy will fail to enable:
{"execute":"migrate-set-capabilities","arguments":{"capabilities":[{"capability":"compress","state":true}]}}
{"return": {}}
{"execute":"migrate-set-capabilities","arguments":{"capabilities":[{"capability":"multifd","state":true}]}}
{"return": {}}
{"execute":"migrate-set-capabilities","arguments":{"capabilities":[{"capability":"zero-copy-send","state":true}]}}
{"error": {"class": "GenericError", "desc": "Zero copy only available for non-compressed non-TLS multifd migration"}}


Additional info:

--- Additional comment from Li Xiaohui on 2022-07-15 15:04:30 CST ---

As libvirt always set all migrate capabilities together through one qmp command "migrate-set-capabilities", we should fix this bug.

--- Additional comment from Li Xiaohui on 2022-07-15 15:23:44 CST ---

BTW, shall we also avoid to enable compress capability successfully if zerocopy enabled like:
{"execute":"migrate-set-capabilities","arguments":{"capabilities":[{"capability":"multifd","state":true}]}}
{"return": {}}
{"execute":"migrate-set-capabilities","arguments":{"capabilities":[{"capability":"zero-copy-send","state":true}]}}
{"return": {}}
{"execute":"migrate-set-capabilities","arguments":{"capabilities":[{"capability":"compress","state":true}]}}
{"return": {}}

--- Additional comment from Leonardo Bras on 2022-07-16 04:41:12 CST ---

Thanks for reporting Li Xiaohui!

I think I have an idea on why this happens, and just wrote a probable fix.

I tested on a scratch build. Could you please give it a try?
https://kojihub.stream.rdu2.redhat.com/koji/taskinfo?taskID=1295372

--- Additional comment from Li Xiaohui on 2022-07-24 17:13:06 CST ---

Thanks Leoardo to provide the scratch build in https://bugzilla.redhat.com/show_bug.cgi?id=1968509#c26.


I have tested the build (qemu-kvm-7.0.0-8.el9.leonardo202207190013.x86_64), the issues in Description, Comment 2 have been fixed, and we also don't support enable xbzrle with zerocopy enabled.


Only following question still exist, do you plan to fix it?
1.When try to migrate with tls + multifd + zerocopy (note tls certs has been set up on source and destination host)
a. if set tls creds on src and dst host firstly, then enable multifd, zerocopy, will get error prompt, it's the expectation:
{"execute": "migrate-set-parameters", "arguments": {"tls-creds": "tls0"}, "id": "hdTiagq5"}
...
{"execute": "migrate-set-capabilities", "arguments": {"capabilities": [{"capability": "zero-copy-send", "state": true}]}, "id": "wgr8gT3T"}
{"id": "wgr8gT3T", "error": {"class": "GenericError", "desc": "Zero copy only available for non-compressed non-TLS multifd migration"}}
b. but if enable multifd, zerocopy firstly, then set tls creds, all will succeed, but when start migration, migration will fail like:
{"execute": "query-migrate", "id": "qUqoTVuL"}
{"return": {"status": "failed", "error-desc": "Requested Zero Copy feature is not available: Invalid argument"}, "id": "qUqoTVuL"}

My question: for situation b, shall we avoid set tls creds successfully when zerocopy is enabled? or give accurate error prompt than above error-desc like zerocopy is enabled, but don't support tls migration under zerocopy.