Hi Cernishov,

> restarted the system several times

the invocation of "ulimit -c unlimited" only affects the current shell and children of it and is not persistent across reboots. The same holds true for direct invocation of "sysctl -w"... so if you ran these steps, then rebooted the machine, then *did not rerun* these steps, you'd see no effect. The same is true if you did not start the VM as a child of the session you increased the core size limit for.

By looking at the content of /proc/<pid>/limits you can see if your changes are effective for your process.

Sending a kill -SEGV to a process should be sufficient to simulate the effect you see for qemu. OTOH, the programmers may have decided to catch that signal within the process and react in their own special way, so there's a slight chance (though not awfully likely) that no core is generated by reason.