Ubuntu Live iso Hangs on XCP-ng 8.1.0; Guest Reports: 'watchdog: BUG: soft lockup' #371

wsciaroni

Hello, I reported a bug and it was closed as not reproducible. I'm curious to know if anyone else has experienced this issue?

I have a fresh install of XCP-NG 8.1. I made sure the pool is fully patched. I have tested this with two known good images of Ubuntu Server 18.04. (18.04.2 and 18.04.4)
When I attempt to start this VM to install Ubuntu Server, I get to the language selection before the VM locks up. On the same host, I was able to boot from and install Debian 10.0 without issue. However, when I go back to any Ubuntu Server image, the vm locks up and I see 100% CPU usage on the guest. I would be happy to provide more information or test with different iso images.
Context

**XCP-ng: 8.1.0
Good behavior with Debian 10.0
Bad behavior with Ubuntu Server 18.04

Expected behavior

When I boot into Ubuntu Server 18.04 Live iso, I should be able to install the OS.
Current behavior

The VM hangs and gives the errors seen in the image below. "watchdog: BUG: soft lockup - CPU#1 stuck for 22s! [lsusb:1887]" and "watchdog: BUG: soft lockup - CPU#2 stuck for 22s! [sfdisk:1777]" alt text

olivierlambert

Thanks for creating the topic here

I can't reproduce the issue, but maybe others in the community could!

Also @wsciaroni what's your hardware?

wsciaroni

@olivierlambert

I am running on a SuperMicro PIO-618U-T4T+-ST031. With a Supermicro X10DRU-i+ motherboard and dual Intel(R) Xeon(R) CPU E5-2640 v3 @ 2.60GHz.

olivierlambert

Do you have any other hardware so you can compare the behavior?

jmccoy555

Just downloaded this iso - http://releases.ubuntu.com/18.04.4/ubuntu-18.04.4-live-server-amd64.iso

Works on my E5-2697v3 and E5-2620 v4 both on a Supermicro X10DRi-T, (only one CPU in exch).

wsciaroni

I do have some other hardware that I could try later. I did notice something that I missed earlier. When I boot into the ubuntu ISO, I see a couple outputs in the console before it gets to the setup area.

[0.887324] vbd vbd-5696: 19 xenbus_dev_probe on device/vbd/5696
[1.172167] piix4_smbus 0000:00:01.3 SMBus Host Controller not enabled!

Maybe this is telling for what could be going on here?

jmccoy555

@wsciaroni just double checked, I see that too very early on and not for long, but then it boots.

wsciaroni

Okay, so maybe that's not the problem.
It does seem very strange that I can boot the Debian 10 ISO, and a CentOS iso, but not an Ubuntu Server ISO...

jmccoy555

Just checked uefi too, that also works.

hoberion

I just tested the http://releases.ubuntu.com/18.04.4/ubuntu-18.04.4-live-server-amd64.iso there was no issue from my side FUJITSU, (,PRIMERGY RX2540 M4,)
latest version xcp-ng / xen orchestra

nbaudet

Hi all,
We are experimenting the same error but with XCP-ng version 8.0.
Our configuration:

XCP-ng version 8.0
VM with Ubuntu server 18.04.1
Server Dell PowerEdge R440 with Intel Xeon Silver 4110 (2,1GHz, 8C/16T, cache 11Mo, 9,6GT/s, 85W, Turbo, HT), mémoire DDR4 2400MHz

We don't have any problem deploying our VM image with Ubuntu server 18.04.1, but randomly when the VM executes we have the following error:
watchdog: BUG: soft lockup - CPU#1 stuck for ...
Then no other choice than restarting the VM.

Note that we have the following warnings after the error:
rcu: INFO: rcu_sched detected expedited stalls on CPUs/tasks: ...
rcu: blocking rcu_nodes structure: ...

As we are getting ready to go to production in the coming month, we will have to change hypervisor if a fix cannot be made. I'm sad to see that the error is still present in v8.1

olivierlambert

As we are getting ready to go to production in the coming month, we will have to change hypervisor if a fix cannot be made. I'm sad to see that the error is still present in v8.1

If you don't report it with details, there's no way we fix a problem we can't reproduce nor spot outside one previous user here.

Obviously, we'll need more details and logs to be able to help.

edit: in other words, we aren't aware of a general problem of this sort. 8.0 (and 8.1) are used intensively by thousands of users around the world. If everyone had issues like this, we would have known. Also it would have been even spotted by Citrix before us.

So the hard task here is to understand why this problem is happening on your side. It can be a bug on XCP-ng code somewhere, due to a specific combo, but it's not widespread.

nbaudet

@olivierlambert
You are absolutely right for the reporting part.
The problem happens randomly and we haven't identified a pattern that would trigger it in a deterministic way.
Now it is reassuring that the problem seems very specific. On our side it occurs on two servers with the exact same configuration.

I would be happy to report details next time it happens. As to be efficient, I would appreciate some specifics on what to report.

Regards

nbaudet

Actually I don't see the Xeon Silver 4110 in Citrix HCL for Hypervisor 8.0.0/8.0.1.
So I don't know if it is worth looking for the root cause.
However I note that wsciaroni reported CPU is listed (Xeon(R) E5-2640 v3)

olivierlambert

I don't think it's a problem on this specific model. Have you run a memtest on this machine?

olivierlambert

Regarding logs to bring: https://xcp-ng.org/docs/troubleshooting.html

nbaudet

Hi Olivier,
I experienced the problem at 14:39:09 today (23/05/2020).
Below some data, hoping it can help.

Context:

1 single physical machine: Server Dell PowerEdge R440 with Intel Xeon Silver 4110 (2,1GHz, 8C/16T, cache 11Mo, 9,6GT/s, 85W, Turbo, HT), mémoire DDR4 2400MHz
XCP-ng version 8.0
2 imported VMs with Ubuntu server 18.04.1
Only one VM sometimes freezes (6 CPU). The other one never does (1 CPU).
The problem occurred when deploying a Kubernetes cluster from the other VM (using Rancher) to the one that froze. Thus, network and CPU were actively used at the time.
Note that I did that same operation around 5 times before on the exact same 2 VMs (deployment tests) with no problem.
See attached screenshot of the frozen VM console output.

Server installation notes

Boot from a USB Key - XCP-ng 8.0. Choose "install" menu entry,
Select a preconfigured RAID10 array to install XCP-ng.
Select the preconfigured RAID10 array for the storage repository (keep the "thick provisioning" option),
Network static configuration (no DNS server).
- ip: 192.168.1.10
- mask: 255.255.255.0
- gateway: 192.168.1.1
Put a random ip for the DNS server (e.g. 172.17.1.4),
No NTP server.
No additional pack installed.

Frozen VM installation notes

CPU=6,
Memory=20GB

"Place all imported virtual disks on this target SR:"
Map the VM network interface to the active server interface.
BIOS Boot
Don't use Operating System Fixup
Network static configuration.
- k8s-node01: 192.168.1.110
- mask: 255.255.255.0
- gateway: 192.168.1.1
Autostart on server boot
Storage 80GB + 2 more partitions added

XCP-ng server log files

The logs below (all from /var/log/) were active during/after the problem occurred.

audit.log
May 23 14:36:09 xcp-ng-yqzvwsgr xapi: [20200523T12:36:09.118Z|audit|xcp-ng-yqzvwsgr|1377881 INET :::80|handler:http/rrd_updates D:64870ad12cf9|audit] ('trackid=4cb8b11fe9c6adddea3b4e09e5503449' 'LOCAL_SUPERUSER' '' 'ALLOWED' 'OK' 'HTTP' 'http/rrd_updates' ())
May 23 14:39:51 xcp-ng-yqzvwsgr xapi: [20200523T12:39:51.967Z|audit|xcp-ng-yqzvwsgr|1377931 INET :::80|handler:http/connect_console D:69721c42e847|audit] ('trackid=ebde3ebf745f529e150f1d1e5657ce01' 'LOCAL_SUPERUSER' 'root' 'ALLOWED' 'OK' 'HTTP' 'http/connect_console' (('ref' '' 'ea88f58c-fc4b-844b-e868-7493d84a5345' 'OpaqueRef:eff0510e-22fb-4a41-aeda-503d5f2922eb')))
May 23 14:39:51 xcp-ng-yqzvwsgr xapi: [20200523T12:39:51.967Z|audit|xcp-ng-yqzvwsgr|1377931 INET :::80|check:http/connect_console/host_console D:014fa9e6b374|audit] ('trackid=ebde3ebf745f529e150f1d1e5657ce01' 'LOCAL_SUPERUSER' 'root' 'ALLOWED' 'OK' 'HTTP' 'http/connect_console/host_console' (('ref' '' 'ea88f58c-fc4b-844b-e868-7493d84a5345' 'OpaqueRef:eff0510e-22fb-4a41-aeda-503d5f2922eb')))
May 23 14:40:00 xcp-ng-yqzvwsgr xapi: [20200523T12:40:00.597Z|audit|xcp-ng-yqzvwsgr|1377932 INET :::80|handler:http/connect_console D:63be5cf43224|audit] ('trackid=ebde3ebf745f529e150f1d1e5657ce01' 'LOCAL_SUPERUSER' 'root' 'ALLOWED' 'OK' 'HTTP' 'http/connect_console' ())
May 23 14:41:12 xcp-ng-yqzvwsgr xapi: [20200523T12:41:12.293Z|audit|xcp-ng-yqzvwsgr|1377948 INET :::80|handler:http/rrd_updates D:d00eb5d5099a|audit] ('trackid=4cb8b11fe9c6adddea3b4e09e5503449' 'LOCAL_SUPERUSER' '' 'ALLOWED' 'OK' 'HTTP' 'http/rrd_updates' ())

xenstored-access.log
May 23 14:40:00 xcp-ng-yqzvwsgr oxenstored: A15 rm /local/domain/22/data/cant_suspend_reason
May 23 14:40:00 xcp-ng-yqzvwsgr oxenstored: A15 rm /local/domain/22/data/cant_suspend_reason
May 23 14:40:00 xcp-ng-yqzvwsgr oxenstored: A1886 write /local/domain/22/data/set_clipboard [omitted]
May 23 14:40:00 xcp-ng-yqzvwsgr oxenstored: A1886 w event /local/domain/22/data/set_clipboard set_clipboard

daemon.log
May 23 14:40:01 xcp-ng-yqzvwsgr systemd[1]: Started Session c23294 of user root.
May 23 14:40:01 xcp-ng-yqzvwsgr systemd[1]: Starting Session c23294 of user root.
May 23 14:40:01 xcp-ng-yqzvwsgr systemd[1]: Started Session c23295 of user root.
May 23 14:40:01 xcp-ng-yqzvwsgr systemd[1]: Starting Session c23295 of user root.

cron
May 23 14:40:01 xcp-ng-yqzvwsgr CROND[11920]: (root) CMD (/usr/lib64/sa/sa1 1 1)
May 23 14:40:01 xcp-ng-yqzvwsgr CROND[11921]: (root) CMD (/opt/xensource/libexec/xapi-logrotate.sh)
May 23 14:45:01 xcp-ng-yqzvwsgr CROND[13202]: (root) CMD (python -c 'import imp; vmss = imp.load_source("vmss", "/etc/xapi.d/plugins/vmss"); vmss.trigger_schedule_snapshots();')

secure
May 23 14:39:40 xcp-ng-yqzvwsgr stunnel: LOG5[3142:140148215760640]: Service [xapi] accepted connection from ::ffff:172.17.1.2:1386
May 23 14:39:40 xcp-ng-yqzvwsgr stunnel: LOG5[3142:140148215760640]: connect_blocking: connected 127.0.0.1:80
May 23 14:39:40 xcp-ng-yqzvwsgr stunnel: LOG5[3142:140148215760640]: Service [xapi] connected remote server from 127.0.0.1:36266
May 23 14:39:44 xcp-ng-yqzvwsgr stunnel: LOG5[3142:140148215650048]: Service [xapi] accepted connection from ::ffff:172.17.1.2:1387
May 23 14:39:44 xcp-ng-yqzvwsgr stunnel: LOG5[3142:140148215650048]: connect_blocking: connected 127.0.0.1:80
May 23 14:39:44 xcp-ng-yqzvwsgr stunnel: LOG5[3142:140148215650048]: Service [xapi] connected remote server from 127.0.0.1:36268
May 23 14:39:44 xcp-ng-yqzvwsgr stunnel: LOG5[3142:140148215871232]: Service [xapi] accepted connection from ::ffff:172.17.1.2:1388
May 23 14:39:44 xcp-ng-yqzvwsgr stunnel: LOG5[3142:140148215871232]: connect_blocking: connected 127.0.0.1:80
May 23 14:39:44 xcp-ng-yqzvwsgr stunnel: LOG5[3142:140148215871232]: Service [xapi] connected remote server from 127.0.0.1:36270
May 23 14:39:44 xcp-ng-yqzvwsgr stunnel: LOG5[3142:140148216092416]: Service [xapi] accepted connection from ::ffff:172.17.1.2:1389
May 23 14:39:44 xcp-ng-yqzvwsgr stunnel: LOG5[3142:140148216092416]: connect_blocking: connected 127.0.0.1:80
May 23 14:39:44 xcp-ng-yqzvwsgr stunnel: LOG5[3142:140148216092416]: Service [xapi] connected remote server from 127.0.0.1:36272
May 23 14:39:51 xcp-ng-yqzvwsgr stunnel: LOG5[3142:140148215981824]: Service [xapi] accepted connection from ::ffff:172.17.1.2:1393
May 23 14:39:51 xcp-ng-yqzvwsgr stunnel: LOG5[3142:140148215981824]: connect_blocking: connected 127.0.0.1:80
May 23 14:39:51 xcp-ng-yqzvwsgr stunnel: LOG5[3142:140148215981824]: Service [xapi] connected remote server from 127.0.0.1:36274
May 23 14:40:00 xcp-ng-yqzvwsgr stunnel: LOG5[3142:140148216162048]: Service [xapi] accepted connection from ::ffff:172.17.1.2:1394
May 23 14:40:00 xcp-ng-yqzvwsgr stunnel: LOG5[3142:140148216162048]: connect_blocking: connected 127.0.0.1:80
May 23 14:40:00 xcp-ng-yqzvwsgr stunnel: LOG5[3142:140148216162048]: Service [xapi] connected remote server from 127.0.0.1:36278
May 23 14:40:18 xcp-ng-yqzvwsgr stunnel: LOG5[3142:140148215981824]: Connection closed: 1231524 byte(s) sent to SSL, 574 byte(s) sent to socket
May 23 14:41:29 xcp-ng-yqzvwsgr stunnel: LOG5[3142:140148215760640]: Connection closed: 1926969 byte(s) sent to SSL, 3880 byte(s) sent to socket
May 23 14:41:29 xcp-ng-yqzvwsgr stunnel: LOG5[3142:140148216092416]: Connection closed: 259 byte(s) sent to SSL, 318 byte(s) sent to socket

xensource.log
May 23 14:38:43 xcp-ng-yqzvwsgr xapi: [debug|xcp-ng-yqzvwsgr|1377916 UNIX /var/lib/xcp/xapi||dummytaskhelper] task dispatch:event.from D:89574dcb797d created by task D:6cdc379c15f1
May 23 14:39:14 xcp-ng-yqzvwsgr xapi: [debug|xcp-ng-yqzvwsgr|1377917 UNIX /var/lib/xcp/xapi||dummytaskhelper] task dispatch:session.logout D:c011a082589a created by task D:6cdc379c15f1
May 23 14:39:14 xcp-ng-yqzvwsgr xapi: [ info|xcp-ng-yqzvwsgr|1377917 UNIX /var/lib/xcp/xapi|session.logout D:76826a82de67|xapi] Session.destroy trackid=8ad18d114c73b897cffa86b75b72bb2c
May 23 14:39:14 xcp-ng-yqzvwsgr xapi: [debug|xcp-ng-yqzvwsgr|1377918 UNIX /var/lib/xcp/xapi||dummytaskhelper] task dispatch:session.slave_login D:edd9206267d2 created by task D:6cdc379c15f1
May 23 14:39:14 xcp-ng-yqzvwsgr xapi: [ info|xcp-ng-yqzvwsgr|1377918 UNIX /var/lib/xcp/xapi|session.slave_login D:75241f399147|xapi] Session.create trackid=02d0588ff3334647fb2a39319b04244f pool=true uname= originator=xapi is_local_superuser=true auth_user_sid= parent=trackid=9834f5af41c964e225f24279aefe4e49
May 23 14:39:14 xcp-ng-yqzvwsgr xapi: [debug|xcp-ng-yqzvwsgr|1377919 UNIX /var/lib/xcp/xapi||dummytaskhelper] task dispatch:pool.get_all D:c6c40733d126 created by task D:75241f399147
May 23 14:39:14 xcp-ng-yqzvwsgr xapi: [debug|xcp-ng-yqzvwsgr|1377920 UNIX /var/lib/xcp/xapi||dummytaskhelper] task dispatch:event.from D:2ceaee79a5d2 created by task D:6cdc379c15f1
May 23 14:39:28 xcp-ng-yqzvwsgr xapi: [debug|xcp-ng-yqzvwsgr|308 |xapi events D:3647b44d7f38|dummytaskhelper] task timeboxed_rpc D:dececb4b9201 created by task D:3647b44d7f38
May 23 14:39:28 xcp-ng-yqzvwsgr xapi: [debug|xcp-ng-yqzvwsgr|1377921 UNIX /var/lib/xcp/xapi||dummytaskhelper] task dispatch:event.from D:e96e0716c10a created by task D:3647b44d7f38
May 23 14:39:41 xcp-ng-yqzvwsgr xapi: [debug|xcp-ng-yqzvwsgr|1377922 INET :::80|session.login_with_password D:57713482620e|xapi] Success: local auth, user root from HTTP request from Internet with User-Agent: XenCenter/8.0.0
May 23 14:39:41 xcp-ng-yqzvwsgr xapi: [ info|xcp-ng-yqzvwsgr|1377922 INET :::80|session.login_with_password D:57713482620e|xapi] Session.create trackid=ebde3ebf745f529e150f1d1e5657ce01 pool=false uname=root originator=XenCenter/8.0.0 is_local_superuser=true auth_user_sid= parent=trackid=9834f5af41c964e225f24279aefe4e49
May 23 14:39:41 xcp-ng-yqzvwsgr xapi: [debug|xcp-ng-yqzvwsgr|1377923 UNIX /var/lib/xcp/xapi||dummytaskhelper] task dispatch:pool.get_all D:4d57f00d74bb created by task D:57713482620e
May 23 14:39:43 xcp-ng-yqzvwsgr xapi: [debug|xcp-ng-yqzvwsgr|1377922 INET :::80|event.from D:dc53f54f253f|xapi] get_since_for_events: last_in_memory (6979) >= since (0): Using slow message lookup
May 23 14:39:45 xcp-ng-yqzvwsgr xapi: [debug|xcp-ng-yqzvwsgr|1377927 UNIX /var/lib/xcp/xapi||dummytaskhelper] task dispatch:session.logout D:a145e5e8112f created by task D:6cdc379c15f1
May 23 14:39:45 xcp-ng-yqzvwsgr xapi: [ info|xcp-ng-yqzvwsgr|1377927 UNIX /var/lib/xcp/xapi|session.logout D:a503679fa7d8|xapi] Session.destroy trackid=02d0588ff3334647fb2a39319b04244f
May 23 14:39:45 xcp-ng-yqzvwsgr xapi: [debug|xcp-ng-yqzvwsgr|1377928 UNIX /var/lib/xcp/xapi||dummytaskhelper] task dispatch:session.slave_login D:a8cd0095ecc3 created by task D:6cdc379c15f1
May 23 14:39:45 xcp-ng-yqzvwsgr xapi: [ info|xcp-ng-yqzvwsgr|1377928 UNIX /var/lib/xcp/xapi|session.slave_login D:8ac76e7704d5|xapi] Session.create trackid=cc258e716a3c1a3f08cb8aa3ed55684c pool=true uname= originator=xapi is_local_superuser=true auth_user_sid= parent=trackid=9834f5af41c964e225f24279aefe4e49
May 23 14:39:45 xcp-ng-yqzvwsgr xapi: [debug|xcp-ng-yqzvwsgr|1377929 UNIX /var/lib/xcp/xapi||dummytaskhelper] task dispatch:pool.get_all D:a6b429562b56 created by task D:8ac76e7704d5
...

The logs below (all from /var/log/) were not active during/after the problem occurred. I tail them because they are mentioned in the troubleshooting page.

SMlog
May 23 12:42:18 xcp-ng-yqzvwsgr SM: [13215] lock: opening lock file /var/lock/sm/aafae74b-fcaf-494c-bf1a-c482603db26b/vdi
May 23 12:42:18 xcp-ng-yqzvwsgr SM: [13215] blktap2.deactivate
May 23 12:42:18 xcp-ng-yqzvwsgr SM: [13215] lock: acquired /var/lock/sm/aafae74b-fcaf-494c-bf1a-c482603db26b/vdi
May 23 12:42:18 xcp-ng-yqzvwsgr SM: [13232] pread SUCCESS
May 23 12:42:18 xcp-ng-yqzvwsgr SM: [13224] pread SUCCESS
May 23 12:42:18 xcp-ng-yqzvwsgr SM: [13232] vdi_deactivate {'sr_uuid': 'ffbb72f2-abd2-818a-937c-2cde97929bf0', 'subtask_of': 'DummyRef:|c059df81-120b-4b97-af44-51f6c7228ede|VDI.deactivate', 'vdi_ref': 'OpaqueRef:34a8263a-80f6-4435-99b8-381490aa87de', 'vdi_on_boot': 'persist', 'args': [], 'vdi_location': 'c3c1bf34-a6cd-4919-b7e5-80e47da03f88', 'host_ref': 'OpaqueRef:37b319c9-5b88-407d-8325-a40f957a81d5', 'session_ref': 'OpaqueRef:ae70fd5a-c67e-4686-b712-0a928ce34898', 'device_config': {'device': '/dev/disk/by-id/scsi-364cd98f0622a1100250a58db11b8c2ae-part3', 'SRmaster': 'true'}, 'command': 'vdi_deactivate', 'vdi_allow_caching': 'false', 'sr_ref': 'OpaqueRef:9ddadcdc-5bda-4b25-ab6f-0543e9295214', 'vdi_uuid': 'c3c1bf34-a6cd-4919-b7e5-80e47da03f88'}

kern.log
May 23 12:42:18 xcp-ng-yqzvwsgr kernel: [6904165.419855] device tap21.0 left promiscuous mode
May 23 12:42:19 xcp-ng-yqzvwsgr kernel: [6904167.073971] device vif21.0 left promiscuous mode
May 23 12:42:24 xcp-ng-yqzvwsgr kernel: [6904171.425112] block tda: sector-size: 512/512 capacity: 209715200
May 23 12:42:24 xcp-ng-yqzvwsgr kernel: [6904171.657529] block tdb: sector-size: 512/512 capacity: 419430400
May 23 12:42:24 xcp-ng-yqzvwsgr kernel: [6904171.876633] block tdc: sector-size: 512/512 capacity: 167780352
May 23 12:42:25 xcp-ng-yqzvwsgr kernel: [6904172.463214] device vif22.0 entered promiscuous mode
May 23 12:42:25 xcp-ng-yqzvwsgr kernel: [6904172.786716] device tap22.0 entered promiscuous mode

$ ll -rt /var/log/installer/
...
-rw-r--r-- 1 root root 524684 Nov 18 2019 install-log

$ ll -rt /var/crash/
total 0

xen-bugtool --yestoall
/var/opt/xen/bug-report/bug-report-20200523145728.tar.bz2
I'll send you this file upon request.

olivierlambert

Hi!

Thanks for the feedback. However, please edit your post to use Markdown syntax to get better visibility on logs files/code blocks.

Then, you should always have a NTP server configured in your hosts, it's very important.

nbaudet

Hi Olivier,
I understand the importance of an NTP server. In the industry I am in, there is usually no Internet access when we deploy on site (for security reasons).
I'll ask but I don't think these networks provide a NTP server.
Do you think this could be somehow linked to the problem we are experiencing?

Below are the logs with better formatting. Let me know if you expect a specific one.

XCP-NG SERVER LOG FILES

The logs below (all from /var/log/) were active during/after the problem occurred.

audit.log

May 23 14:36:09 xcp-ng-yqzvwsgr xapi: [20200523T12:36:09.118Z|audit|xcp-ng-yqzvwsgr|1377881 INET :::80|handler:http/rrd_updates D:64870ad12cf9|audit] ('trackid=4cb8b11fe9c6adddea3b4e09e5503449' 'LOCAL_SUPERUSER' '' 'ALLOWED' 'OK' 'HTTP' 'http/rrd_updates' ())
May 23 14:39:51 xcp-ng-yqzvwsgr xapi: [20200523T12:39:51.967Z|audit|xcp-ng-yqzvwsgr|1377931 INET :::80|handler:http/connect_console D:69721c42e847|audit] ('trackid=ebde3ebf745f529e150f1d1e5657ce01' 'LOCAL_SUPERUSER' 'root' 'ALLOWED' 'OK' 'HTTP' 'http/connect_console' (('ref' '' 'ea88f58c-fc4b-844b-e868-7493d84a5345' 'OpaqueRef:eff0510e-22fb-4a41-aeda-503d5f2922eb')))
May 23 14:39:51 xcp-ng-yqzvwsgr xapi: [20200523T12:39:51.967Z|audit|xcp-ng-yqzvwsgr|1377931 INET :::80|check:http/connect_console/host_console D:014fa9e6b374|audit] ('trackid=ebde3ebf745f529e150f1d1e5657ce01' 'LOCAL_SUPERUSER' 'root' 'ALLOWED' 'OK' 'HTTP' 'http/connect_console/host_console' (('ref' '' 'ea88f58c-fc4b-844b-e868-7493d84a5345' 'OpaqueRef:eff0510e-22fb-4a41-aeda-503d5f2922eb')))
May 23 14:40:00 xcp-ng-yqzvwsgr xapi: [20200523T12:40:00.597Z|audit|xcp-ng-yqzvwsgr|1377932 INET :::80|handler:http/connect_console D:63be5cf43224|audit] ('trackid=ebde3ebf745f529e150f1d1e5657ce01' 'LOCAL_SUPERUSER' 'root' 'ALLOWED' 'OK' 'HTTP' 'http/connect_console' ())
May 23 14:41:12 xcp-ng-yqzvwsgr xapi: [20200523T12:41:12.293Z|audit|xcp-ng-yqzvwsgr|1377948 INET :::80|handler:http/rrd_updates D:d00eb5d5099a|audit] ('trackid=4cb8b11fe9c6adddea3b4e09e5503449' 'LOCAL_SUPERUSER' '' 'ALLOWED' 'OK' 'HTTP' 'http/rrd_updates' ())

xenstored-access.log

May 23 14:40:00 xcp-ng-yqzvwsgr oxenstored: A15 rm /local/domain/22/data/cant_suspend_reason
May 23 14:40:00 xcp-ng-yqzvwsgr oxenstored: A15 rm /local/domain/22/data/cant_suspend_reason
May 23 14:40:00 xcp-ng-yqzvwsgr oxenstored: A1886 write /local/domain/22/data/set_clipboard [omitted]
May 23 14:40:00 xcp-ng-yqzvwsgr oxenstored: A1886 w event /local/domain/22/data/set_clipboard set_clipboard

daemon.log

May 23 14:40:01 xcp-ng-yqzvwsgr systemd[1]: Started Session c23294 of user root.
May 23 14:40:01 xcp-ng-yqzvwsgr systemd[1]: Starting Session c23294 of user root.
May 23 14:40:01 xcp-ng-yqzvwsgr systemd[1]: Started Session c23295 of user root.
May 23 14:40:01 xcp-ng-yqzvwsgr systemd[1]: Starting Session c23295 of user root.

cron

May 23 14:40:01 xcp-ng-yqzvwsgr CROND[11920]: (root) CMD (/usr/lib64/sa/sa1 1 1)
May 23 14:40:01 xcp-ng-yqzvwsgr CROND[11921]: (root) CMD (/opt/xensource/libexec/xapi-logrotate.sh)
May 23 14:45:01 xcp-ng-yqzvwsgr CROND[13202]: (root) CMD (python -c 'import imp; vmss = imp.load_source("vmss", "/etc/xapi.d/plugins/vmss"); vmss.trigger_schedule_snapshots();')

secure

May 23 14:39:40 xcp-ng-yqzvwsgr stunnel: LOG5[3142:140148215760640]: Service [xapi] accepted connection from ::ffff:172.17.1.2:1386
May 23 14:39:40 xcp-ng-yqzvwsgr stunnel: LOG5[3142:140148215760640]: connect_blocking: connected 127.0.0.1:80
May 23 14:39:40 xcp-ng-yqzvwsgr stunnel: LOG5[3142:140148215760640]: Service [xapi] connected remote server from 127.0.0.1:36266
May 23 14:39:44 xcp-ng-yqzvwsgr stunnel: LOG5[3142:140148215650048]: Service [xapi] accepted connection from ::ffff:172.17.1.2:1387
May 23 14:39:44 xcp-ng-yqzvwsgr stunnel: LOG5[3142:140148215650048]: connect_blocking: connected 127.0.0.1:80
May 23 14:39:44 xcp-ng-yqzvwsgr stunnel: LOG5[3142:140148215650048]: Service [xapi] connected remote server from 127.0.0.1:36268
May 23 14:39:44 xcp-ng-yqzvwsgr stunnel: LOG5[3142:140148215871232]: Service [xapi] accepted connection from ::ffff:172.17.1.2:1388
May 23 14:39:44 xcp-ng-yqzvwsgr stunnel: LOG5[3142:140148215871232]: connect_blocking: connected 127.0.0.1:80
May 23 14:39:44 xcp-ng-yqzvwsgr stunnel: LOG5[3142:140148215871232]: Service [xapi] connected remote server from 127.0.0.1:36270
May 23 14:39:44 xcp-ng-yqzvwsgr stunnel: LOG5[3142:140148216092416]: Service [xapi] accepted connection from ::ffff:172.17.1.2:1389
May 23 14:39:44 xcp-ng-yqzvwsgr stunnel: LOG5[3142:140148216092416]: connect_blocking: connected 127.0.0.1:80
May 23 14:39:44 xcp-ng-yqzvwsgr stunnel: LOG5[3142:140148216092416]: Service [xapi] connected remote server from 127.0.0.1:36272
May 23 14:39:51 xcp-ng-yqzvwsgr stunnel: LOG5[3142:140148215981824]: Service [xapi] accepted connection from ::ffff:172.17.1.2:1393
May 23 14:39:51 xcp-ng-yqzvwsgr stunnel: LOG5[3142:140148215981824]: connect_blocking: connected 127.0.0.1:80
May 23 14:39:51 xcp-ng-yqzvwsgr stunnel: LOG5[3142:140148215981824]: Service [xapi] connected remote server from 127.0.0.1:36274
May 23 14:40:00 xcp-ng-yqzvwsgr stunnel: LOG5[3142:140148216162048]: Service [xapi] accepted connection from ::ffff:172.17.1.2:1394
May 23 14:40:00 xcp-ng-yqzvwsgr stunnel: LOG5[3142:140148216162048]: connect_blocking: connected 127.0.0.1:80
May 23 14:40:00 xcp-ng-yqzvwsgr stunnel: LOG5[3142:140148216162048]: Service [xapi] connected remote server from 127.0.0.1:36278
May 23 14:40:18 xcp-ng-yqzvwsgr stunnel: LOG5[3142:140148215981824]: Connection closed: 1231524 byte(s) sent to SSL, 574 byte(s) sent to socket
May 23 14:41:29 xcp-ng-yqzvwsgr stunnel: LOG5[3142:140148215760640]: Connection closed: 1926969 byte(s) sent to SSL, 3880 byte(s) sent to socket
May 23 14:41:29 xcp-ng-yqzvwsgr stunnel: LOG5[3142:140148216092416]: Connection closed: 259 byte(s) sent to SSL, 318 byte(s) sent to socket

xensource.log

May 23 14:38:43 xcp-ng-yqzvwsgr xapi: [debug|xcp-ng-yqzvwsgr|1377916 UNIX /var/lib/xcp/xapi||dummytaskhelper] task dispatch:event.from D:89574dcb797d created by task D:6cdc379c15f1
May 23 14:39:14 xcp-ng-yqzvwsgr xapi: [debug|xcp-ng-yqzvwsgr|1377917 UNIX /var/lib/xcp/xapi||dummytaskhelper] task dispatch:session.logout D:c011a082589a created by task D:6cdc379c15f1
May 23 14:39:14 xcp-ng-yqzvwsgr xapi: [ info|xcp-ng-yqzvwsgr|1377917 UNIX /var/lib/xcp/xapi|session.logout D:76826a82de67|xapi] Session.destroy trackid=8ad18d114c73b897cffa86b75b72bb2c
May 23 14:39:14 xcp-ng-yqzvwsgr xapi: [debug|xcp-ng-yqzvwsgr|1377918 UNIX /var/lib/xcp/xapi||dummytaskhelper] task dispatch:session.slave_login D:edd9206267d2 created by task D:6cdc379c15f1
May 23 14:39:14 xcp-ng-yqzvwsgr xapi: [ info|xcp-ng-yqzvwsgr|1377918 UNIX /var/lib/xcp/xapi|session.slave_login D:75241f399147|xapi] Session.create trackid=02d0588ff3334647fb2a39319b04244f pool=true uname= originator=xapi is_local_superuser=true auth_user_sid= parent=trackid=9834f5af41c964e225f24279aefe4e49
May 23 14:39:14 xcp-ng-yqzvwsgr xapi: [debug|xcp-ng-yqzvwsgr|1377919 UNIX /var/lib/xcp/xapi||dummytaskhelper] task dispatch:pool.get_all D:c6c40733d126 created by task D:75241f399147
May 23 14:39:14 xcp-ng-yqzvwsgr xapi: [debug|xcp-ng-yqzvwsgr|1377920 UNIX /var/lib/xcp/xapi||dummytaskhelper] task dispatch:event.from D:2ceaee79a5d2 created by task D:6cdc379c15f1
May 23 14:39:28 xcp-ng-yqzvwsgr xapi: [debug|xcp-ng-yqzvwsgr|308 |xapi events D:3647b44d7f38|dummytaskhelper] task timeboxed_rpc D:dececb4b9201 created by task D:3647b44d7f38
May 23 14:39:28 xcp-ng-yqzvwsgr xapi: [debug|xcp-ng-yqzvwsgr|1377921 UNIX /var/lib/xcp/xapi||dummytaskhelper] task dispatch:event.from D:e96e0716c10a created by task D:3647b44d7f38
May 23 14:39:41 xcp-ng-yqzvwsgr xapi: [debug|xcp-ng-yqzvwsgr|1377922 INET :::80|session.login_with_password D:57713482620e|xapi] Success: local auth, user root from HTTP request from Internet with User-Agent: XenCenter/8.0.0
May 23 14:39:41 xcp-ng-yqzvwsgr xapi: [ info|xcp-ng-yqzvwsgr|1377922 INET :::80|session.login_with_password D:57713482620e|xapi] Session.create trackid=ebde3ebf745f529e150f1d1e5657ce01 pool=false uname=root originator=XenCenter/8.0.0 is_local_superuser=true auth_user_sid= parent=trackid=9834f5af41c964e225f24279aefe4e49
May 23 14:39:41 xcp-ng-yqzvwsgr xapi: [debug|xcp-ng-yqzvwsgr|1377923 UNIX /var/lib/xcp/xapi||dummytaskhelper] task dispatch:pool.get_all D:4d57f00d74bb created by task D:57713482620e
May 23 14:39:43 xcp-ng-yqzvwsgr xapi: [debug|xcp-ng-yqzvwsgr|1377922 INET :::80|event.from D:dc53f54f253f|xapi] get_since_for_events: last_in_memory (6979) >= since (0): Using slow message lookup
May 23 14:39:45 xcp-ng-yqzvwsgr xapi: [debug|xcp-ng-yqzvwsgr|1377927 UNIX /var/lib/xcp/xapi||dummytaskhelper] task dispatch:session.logout D:a145e5e8112f created by task D:6cdc379c15f1
May 23 14:39:45 xcp-ng-yqzvwsgr xapi: [ info|xcp-ng-yqzvwsgr|1377927 UNIX /var/lib/xcp/xapi|session.logout D:a503679fa7d8|xapi] Session.destroy trackid=02d0588ff3334647fb2a39319b04244f
May 23 14:39:45 xcp-ng-yqzvwsgr xapi: [debug|xcp-ng-yqzvwsgr|1377928 UNIX /var/lib/xcp/xapi||dummytaskhelper] task dispatch:session.slave_login D:a8cd0095ecc3 created by task D:6cdc379c15f1
May 23 14:39:45 xcp-ng-yqzvwsgr xapi: [ info|xcp-ng-yqzvwsgr|1377928 UNIX /var/lib/xcp/xapi|session.slave_login D:8ac76e7704d5|xapi] Session.create trackid=cc258e716a3c1a3f08cb8aa3ed55684c pool=true uname= originator=xapi is_local_superuser=true auth_user_sid= parent=trackid=9834f5af41c964e225f24279aefe4e49
May 23 14:39:45 xcp-ng-yqzvwsgr xapi: [debug|xcp-ng-yqzvwsgr|1377929 UNIX /var/lib/xcp/xapi||dummytaskhelper] task dispatch:pool.get_all D:a6b429562b56 created by task D:8ac76e7704d5
...

The logs below (all from /var/log/) were not active during/after the problem occurred. I tail them because they are mentioned in the troubleshooting page.
SMlog

May 23 12:42:18 xcp-ng-yqzvwsgr SM: [13215] lock: opening lock file /var/lock/sm/aafae74b-fcaf-494c-bf1a-c482603db26b/vdi
May 23 12:42:18 xcp-ng-yqzvwsgr SM: [13215] blktap2.deactivate
May 23 12:42:18 xcp-ng-yqzvwsgr SM: [13215] lock: acquired /var/lock/sm/aafae74b-fcaf-494c-bf1a-c482603db26b/vdi
May 23 12:42:18 xcp-ng-yqzvwsgr SM: [13232] pread SUCCESS
May 23 12:42:18 xcp-ng-yqzvwsgr SM: [13224] pread SUCCESS
May 23 12:42:18 xcp-ng-yqzvwsgr SM: [13232] vdi_deactivate {'sr_uuid': 'ffbb72f2-abd2-818a-937c-2cde97929bf0', 'subtask_of': 'DummyRef:|c059df81-120b-4b97-af44-51f6c7228ede|VDI.deactivate', 'vdi_ref': 'OpaqueRef:34a8263a-80f6-4435-99b8-381490aa87de', 'vdi_on_boot': 'persist', 'args': [], 'vdi_location': 'c3c1bf34-a6cd-4919-b7e5-80e47da03f88', 'host_ref': 'OpaqueRef:37b319c9-5b88-407d-8325-a40f957a81d5', 'session_ref': 'OpaqueRef:ae70fd5a-c67e-4686-b712-0a928ce34898', 'device_config': {'device': '/dev/disk/by-id/scsi-364cd98f0622a1100250a58db11b8c2ae-part3', 'SRmaster': 'true'}, 'command': 'vdi_deactivate', 'vdi_allow_caching': 'false', 'sr_ref': 'OpaqueRef:9ddadcdc-5bda-4b25-ab6f-0543e9295214', 'vdi_uuid': 'c3c1bf34-a6cd-4919-b7e5-80e47da03f88'}

kern.log

May 23 12:42:18 xcp-ng-yqzvwsgr kernel: [6904165.419855] device tap21.0 left promiscuous mode
May 23 12:42:19 xcp-ng-yqzvwsgr kernel: [6904167.073971] device vif21.0 left promiscuous mode
May 23 12:42:24 xcp-ng-yqzvwsgr kernel: [6904171.425112] block tda: sector-size: 512/512 capacity: 209715200
May 23 12:42:24 xcp-ng-yqzvwsgr kernel: [6904171.657529] block tdb: sector-size: 512/512 capacity: 419430400
May 23 12:42:24 xcp-ng-yqzvwsgr kernel: [6904171.876633] block tdc: sector-size: 512/512 capacity: 167780352
May 23 12:42:25 xcp-ng-yqzvwsgr kernel: [6904172.463214] device vif22.0 entered promiscuous mode
May 23 12:42:25 xcp-ng-yqzvwsgr kernel: [6904172.786716] device tap22.0 entered promiscuous mode

$ ll -rt /var/crash/
total 0

I'll send you the below report file or the install-log one upon request.

xen-bugtool --yestoall
/var/opt/xen/bug-report/bug-report-20200523145728.tar.bz2

olivierlambert

If you don't want to rely on an external NTP, you can have a local NTP machine, to at least sync all hosts internally.

It's more important to have the same time on the same site for every machine than having the "right universal time" only partially (not on all machines)