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Hello,
we are observing random PV domU segfaults on Intel based systems with XPTI enabled. These segfaults were not present in Xen 4.9.2 and can be reproduced on 4.9.3/4.10.2/4.11.1. The problem can be mitigated by adding xpti=false to xen command line options.

Some of the affected systems are Debian 8/9 (Debian 10 with kernel 4.18 seems to work fine) and NetBSD 7. It's harder to reproduce the segfaults on Debian, but on NetBSD it's almost instant.

The 7.0 files can be taken from:
https://cdn.netbsd.org/pub/NetBSD/NetBSD-7.0/amd64/binary/kernel/netbsd-INSTALL_XEN3_DOMU.gz
https://cdn.netbsd.org/pub/NetBSD/NetBSD-7.0/amd64/binary/kernel/netbsd-XEN3_DOMU.gz

netbsd.conf:
kernel = "7.0/netbsd-INSTALL_XEN3_DOMU.gz"
memory = 512
vcpus = 1
name = "netbsd"
vif = [ '' ]
disk = ['phy:/dev/vg_data/netbsd,xvda,w']

The installation goes fine, but in the end:

     Status: Command failed
    Command: /bin/sh MAKEDEV all
     Hit enter to continue
--------------------------------------------------------------------------------
[1]   Done                    eval "${before}"... |
      Segmentation fault (core dumped) eval "${after}";...
[1]   Done                    eval "${before}"... |
      Segmentation fault (core dumped) eval "${after}";...

Now we boot the system with changing kernel to:
kernel = "7.0/netbsd-XEN3_DOMU.gz"

...
Updating motd.
Starting powerd.
[1]   Segmentation fault (core dumped) sysctl -n hw.dis...
/usr/sbin/postconf: warning: valid_hostname: misplaced delimiter: .domain.tld
/usr/sbin/postconf: fatal: unable to use my own hostname
Jan 11 05:49:49 .sygic postfix[1550]: fatal: unable to use my own hostname
/etc/rc.d/postfix exited with code 1
Starting inetd.
...

Is it a known issue or can something be done with this?

Thank you,
Tomas

[Xen-users] xen domU segfaults with xpti on intel based systems