What were you trying to do that didn't work?
Report a warning when memory-backend-file is configured without 'prealloc=true', especially for those scenarios where hugetlb or tmpfs filesystems are used, this way a QEMU core dump will be avoided when running out of memory or the user will be properly informed about the misconfiguration.

Please provide the package NVR for which bug is seen:

How reproducible:

Steps to reproduce
1. Launch QEMU including a memory-backend-file object backed in some hugetlb/tmpfs location looking for an out of memory and consequently QEMU core dump

Expected results
A warning message about the misconfiguration that opportunistically avoids the core dump or at least informs the user

Actual results
No warning message about the misconfiguration