Bug 2001316

+++ This bug was initially created as a clone of Bug #1984721 +++

Description of problem:
unclear error message while hotplugging the same chardev


Version-Release number of selected component (if applicable):
Host:    
    kernel-4.18.0-323.el8.x86_64 
    qemu-kvm-6.0.0-24.module+el8.5.0+11844+1e3017bd.x86_64
    



How reproducible: 100%


Steps to Reproduce:
1. Boot qemu with cmdline:
   /usr/libexec/qemu-kvm -monitor stdio -qmp tcp:0:4445,server=on,wait=off

2. Hotplug chardev:
  {"execute":"chardev-add","arguments":{"id":"char2","backend":{"type":"socket","data":{"addr":{"type":"unix", "data": {"path": "/home/mm"}}}}}}
  {"return": {}}

3. Hotplug the same chardev again:
  {"execute":"chardev-add","arguments":{"id":"char2","backend":{"type":"socket","data":{"addr":{"type":"unix", "data": {"path": "/home/mm"}}}}}}
  {"error": {"class": "GenericError", "desc": "duplicate yank instance"}}

Actual results:
Can't tell what's the reason that cause the failure of hotplugging.


Expected results:
We should have reported
that the "id" value for the two chardevs is clashing.


Additional info:

--- Additional comment from liunana on 2021-07-22 02:43:42 UTC ---

Slow train has no such issue:
    qemu-kvm-4.2.0-53.module+el8.5.0+11673+72138537.x86_64


{"execute":"chardev-add","arguments":{"id":"char2","backend":{"type":"socket","data":{"addr":{"type":"unix", "data": {"path": "/home/mm"}}}}}}
{"return": {}}
{"execute":"chardev-add","arguments":{"id":"char2","backend":{"type":"socket","data":{"addr":{"type":"unix", "data": {"path": "/home/mm"}}}}}}
{"error": {"class": "GenericError", "desc": "attempt to add duplicate property 'char2' to object (type 'container')"}}

--- Additional comment from Marc-Andre Lureau on 2021-07-28 11:34:05 UTC ---


Would this be good enough?

{"error": {"class": "GenericError", "desc": "Failed to open chardev 'char2': duplicate yank instance"}}


> {"error": {"class": "GenericError", "desc": "attempt to add duplicate property 'char2' to object (type 'container')"}}

wasn't very friendly either..

--- Additional comment from liunana on 2021-07-30 09:39:31 UTC ---

(In reply to Marc-Andre Lureau from comment #2)
> Would this be good enough?
> 
> {"error": {"class": "GenericError", "desc": "Failed to open chardev 'char2':
> duplicate yank instance"}}
> 

Hi,

It's good to contain the duplicate chardev id, thanks.
But seems 'open chardev' is not a match error log for duplicate hotplugging the same chardev.

How about:

{"error": {"class": "GenericError", "desc": "Failed to add chardev 'char2': duplicate yank instance"}}



Besides, would you please help to explain more about what's the 'yank' function in the error log? Thanks.


> 
> > {"error": {"class": "GenericError", "desc": "attempt to add duplicate property 'char2' to object (type 'container')"}}
> 
> wasn't very friendly either.


Seems clearer than "duplicate yank instance".




Best regards
Liu Nana

--- Additional comment from John Ferlan on 2021-08-09 13:25:32 UTC ---

Moving this to 8.6, in POST, and setting DTM=5 since this can be tested/validated using the weekly rebase as the fix has gone into qemu-6.1.

Decision was to not backport for AV 8.5 since it's really an error path for newer code (yank functionality) that isn't necessarily reachable via libvirt or other means at this point. Neither RHV nor OSP will use 8.5.