Re: xenstored: EACCESS error accessing control/feature-balloon 1

[zithro <slack@xxxxxxxxx>]

On 04 May 2023 17:59, Yann Dirson wrote:
> On 5/4/23 15:58, zithro wrote:
> > Hi,
> >
> > [ snipped for brevity, report summary:
> > XAPI daemon in domU tries to write to a non-existent xenstore node in
> > a non-XAPI dom0 ]
> >
> > On 12 Apr 2023 18:41, Yann Dirson wrote:
> > > Is there anything besides XAPI using this node, or the other data
> > > published by xe-daemon?
> > On my vanilla Xen (ie. non-XAPI), I have no node about "balloon"-ing
> > in xenstore (either dom0 or domU nodes, but I'm not using ballooning
> > in both).
> >
> > > Maybe the original issue is just that there is no reason to have
> > > xe-guest-utilities installed in this setup?
> > That's what I thought as I'm not using XAPI, so maybe the problem
> > should only be addressed to the truenas team ? I posted on their forum
> > but got no answer.
> > I killed the 'xe-daemon' in both setups without loss of functionality.
> >
> > My wild guess is that 'xe-daemon', 'xe-update-guest-attrs' and all
> > 'xenstore* commands' are leftovers from when Xen was working as a dom0
> > under FreeBSD (why would a *domU* have them ?).
> That would not be correct: xenstore* are useful in guests, should you
> want to read/write to the XenStore manually or from scripts;
Didn't know that, can you give some use cases (or URLs) for which it is 
useful, with or without XAPI ?
I've read xenstore* man pages and could not infer a use case.
Although I may already see some : updating ballooned memory values, or 
as Julien Grall pointed out, updating "feature-s3/4" values ?
PS: small mistake in "man/xenstore-write.1.html" (from at least 4.14, 
and onward), the synopsis reads "xenstore-read" ieof "xenstore-read".
Also, the -s option disappeared from unstable, although it may be 
expected. I don't know it's purpose either.
> xe-deamon and xe-update-guest-attrs both come from xe-guest-utilities 6.x, which
> is really a domU tool as well, but is there to support XAPI in dom0.
I checked on freshports, this is effectively the last version in 
FreeBSD, hence FreeNAS (although the version number hasn't been updated 
since 2020, despite updates, so it's not clear which version I'm using).
So next question is: shouldn't the installer detect if running on a XAPI 
Xen or not ? I imagine it's feasible, maybe via XAPI-specific xenstore 
nodes ?
Have a nice evening