[Pkg-xen-devel] Ubuntu delta against 4.5.0-1 in experimental for disussion

[Stefan Bader]

On 22.01.2015 17:02, Ian Campbell wrote:
> On Thu, 2015-01-22 at 13:02 +0100, Stefan Bader wrote:
>> That one modifies xen-init-list to look at domains managed by the xl namespace.
>> This additionally works around a bug in xl which will report a syntax error when
>> "xl list -l" is called while domains in a different namespace exist. Which is
>> the case when libvirt is used to start them.
> 
> FWIW in 4.5 xl is supposed to be more tolerant of domains started by
> another toolstack (so long as they are using the libxl framework). In
> particular I think "xl list -l" is supposed to cope with libvirt domains
> now.

Did some more hands-on testing now and it looks like the old problem is indeed
fixed. Though there is now a

libxl: error: libxl.c:6571:libxl_retrieve_domain_configuration: fail to get
domain configuration for domain 0

But that does not look to be causing problems. Something to think about here is
more subtle and rather a question of policy. So the output of xen-init-list is,
either solely or also, used to act on running domains when the host is shut down.

For libvirt there is a similar aproach in its init script. By default (did not
dig deep enough there to know whether that is only our or upstream) this
connects via qemu and lxc uris and shuts down guests. Adding the xen uri sounds
logical as this covers all cases of guests managed via libvirt then.

But then "xl list -l" does not appear to make a difference between domains
started by itself or other toolstacks now. So xendomains would act on all of
them. May or may not be a problem right now. But at least could lead to
unexpected behaviour. Which could become worse when init scripts are handled
more in parallel.

This is not only a problem in Debian or Ubuntu. We should probably discuss this
more widely. Just brought it up here as the change to xen-init-list not only
works around the bug (which is no longer present) but also causes it to only
print details of domains started by xl (and so leaving libvirt started domains
to be handled by libvirt).

-Stefan
> 
>> diff -Nru xen-4.5.0/debian/xen-utils-common.xen.init
>> xen-4.5.0/debian/xen-utils-common.xen.init
>> --- xen-4.5.0/debian/xen-utils-common.xen.init	2015-01-20 19:29:03.000000000 +0100
>> +++ xen-4.5.0/debian/xen-utils-common.xen.init	2015-01-22 12:16:25.000000000 +0100
>> @@ -37,6 +37,9 @@
>>  XENCONSOLED_PIDFILE="/var/run/xenconsoled.pid"
>>  XENSTORED="$ROOT"/bin/xenstored
>>  XENSTORED_PIDFILE="/var/run/xenstore.pid"
>> +QEMU=/usr/bin/qemu-system-i386
>> +QEMU_PIDFILE="/var/run/qemu-dom0.pid"
>> +QEMU_ARGS="-xen-domid 0 -xen-attach -name dom0 -nographic -M xenpv -daemonize
>> -monitor /dev/null -serial /dev/null -parallel /dev/null"
> 
> I think all this is #770456, feature/bug770456 branch in the packaging
> xen.git. TBH I think this really ought to be fixed for Jessie.
> 
> Ian.
> 


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