xenstored: EACCESS error accessing control/feature-balloon 1

[zithro <slack@xxxxxxxxx>]

Hi all,

this is what I have in "xenstored-access.log" in dom0 :

[20230411T23:48:27.917Z]  D5         write     control/feature-balloon 1
[20230411T23:48:27.917Z]  D5         error     EACCES
[20230411T23:48:27.923Z]  D5         write     data/updated Wed Apr 12 
01:48:27 CEST 2023
It happens once each minute, on two different hosts, both amd64.
(both hosts using the same config, only the hardware differs).

I tried looking up for a similar bug, but didn't find one.
I apologize in advance if this error is known, and if this is not the
place to report this !

-----------------------
Technical infos
-----------------------
dom0s:

Debian stable, kernel 5.10.0-21-amd64
Xen 4.14.5
xl.conf has : autoballoon="0"
GRUB_CMDLINE_XEN="dom0_mem=2048M,max:2048M dom0_max_vcpus=4 
dom0_vcpus_pin loglvl=all guest_loglvl=all ucode=scan iommu=verbose"
Running "xenstore-ls -f -p | grep balloon" returns no result
-----------------------
domUs (D5 in above logs):

HVM TrueNAS Core, based on FreeBSD 13.1-RELEASE-p7
(it happened also on previous FreeBSD realeases, but don't remember when
it started, logs have been filled and rotated).
In cfg files, using either the same value for "memory" and "maxmem" or 
only setting "memory" give the same results.
What's strange is that I have xen* commands in FreeNAS :

xen-detect        xenstore-control  xenstore-ls       xenstore-watch
xenstore          xenstore-exists   xenstore-read     xenstore-write
xenstore-chmod    xenstore-list     xenstore-rm

root@truenas[~]# xenstore-ls
xenstore-ls: xs_directory (/): Permission denied

root@truenas[~]# ps aux
root   [...]     0:36.98 [xenwatch]
root   [...]     0:01.01 [xenstore_rcv]
root   [...]     0:00.00 [balloon]
root   [...]     0:01.74 /bin/sh /usr/local/sbin/xe-daemon -p 
/var/run/xe-daemon.pid
[...]

The xe-daemon looks strange also, I don't use XenServer/XCP-ng, only
"raw" Xen.
And this script which hand

I also use PFsense domUs (based on FreeBSD), but they don't exhibit
this behaviour (ie. no xenstore access error in dom0, no xen*
commands in domU).

So is this a problem with TrueNAS rather than with Xen ?
If so I apologize for wasting your time.

Thanks, have a nice day !
(and as it's my first post here: thx for Xen, it rocks)

zithro