signal 4 (SIGILL) with PHP-FPM 7.3 or 7.4 on 8.1 PV Guest on Citrix Xenserver 7.0

[Bartosz Maciejewski <bartosz%maciejewski.org@localhost>]

Hello,

after upgrading from PHP 7.1 to 7.4 I started noticing this kind of 
errors in php-fpm log

[29-Apr-2020 13:17:19] NOTICE: fpm is running, pid 26497
[29-Apr-2020 13:17:22] NOTICE: ready to handle connections
[29-Apr-2020 13:19:18] WARNING: [pool www] child 5629 exited on signal 4 
(SIGILL) after 117.236785 seconds from start
[29-Apr-2020 13:19:18] NOTICE: [pool www] child 16921 started
[29-Apr-2020 13:19:19] WARNING: [pool www] child 681 exited on signal 4 
(SIGILL) after 118.987485 seconds from start
[29-Apr-2020 13:19:19] NOTICE: [pool www] child 6459 started

After reverting snapshot to before upgrade to 7.4 and upgrading to PHP 
7.2 - all is working, then upgrading to PHP7.3 or 7.4 causes warnings 
and websites are unusable (nginx, php-fpm, worpdress, mysql). Both PHP 
7.3 and 7.4 from pksgrsc 2020Q1 - 7.3.17 and 7.4.4

There are very few informations on the web regarding this kind of error, 
I found two links that are pointing that this is ue to Xen as 
hypervisor, and guest are in PV mode:

https://forums.cpanel.net/resources/kvm-xen-hw_aes-detection-issues-yum-update-illegal-instruction.435/
https://gryzli.info/2016/05/28/centos-6-curl-ssl-illegal-instruction-error/

Unfortunately, none of proposed fixes took any effect.

Any help getting PHP 7.4 with FPM on 8.1 PV on Xencerver 7.0 welcome.

I will try to upgrade NetBSD to 9.0 to see if this helps, I will also 
try to convert PV guest to HVM, but don't know how yet, simple change of 
kernel and change of xbd to wd in fstab doesn't work.