This looks like the host is running CentOS, with packages dating from approx 7.3. This is very outdated given current version is 7.6. So I don't think it is worth spending time to debug until the host OS is upgraded to the latest QEMU/libvirt/kernel packages at least to see if the problem still reproduces.
> # libvirtd -V qemu-kvm --version ev-2.6. 0-28.el7_ 3.6.1), Copyright (c) 2003-2008 Fabrice Bellard
> libvirtd (libvirt) 3.9.0
>
> # /usr/libexec/
> QEMU emulator version 2.6.0 (qemu-kvm-
This looks like the host is running CentOS, with packages dating from approx 7.3. This is very outdated given current version is 7.6. So I don't think it is worth spending time to debug until the host OS is upgraded to the latest QEMU/libvirt/kernel packages at least to see if the problem still reproduces.