What were you trying to do that didn't work?

When setting a guest vm with virtio-mem device and memory backing with preallocation and hugepage enabled. Start the guest then check qemu cmdline find that virtio-mem memory is not preallocated is not set correctly.

Please provide the package NVR for which the bug is seen:

# rpm -q libvirt qemu-kvm
libvirt-11.2.0-1.el10.s390x
qemu-kvm-10.0.0-0.rc3.el10.preview.s390x

How reproducible is this bug?:100%

Steps to reproduce

1. enable kvm hugepage support on s390x

# modprobe -r kvm
# modprobe kvm hpage=1

1. allocate hugepages

# echo 3072 > /sys/kernel/mm/hugepages/hugepages-1024kB/nr_hugepages

1. Define a guest with below config:
   <maxMemory unit='KiB'>15242880</maxMemory>
     <memory unit='KiB'>3145728</memory>
     <currentMemory unit='KiB'>1048576</currentMemory>
   <memoryBacking>
             <hugepages/>
             <allocation mode="immediate" threads='8'/>
     </memoryBacking>
   ...
   <memory model='virtio-mem' >
       <target>
         <size unit='KiB'>2097152</size>
         <block unit='KiB'>1024</block>
         <requested unit='KiB'>2097152</requested>
       </target>
     </memory>
2. Start the guest

# virsh start avocado-vt-vm1
Domain 'avocado-vt-vm1' started

1. Check the qemu cmdline
2. ps -ef | grep qemu-kvm
   ... -object {"qom-type":"memory-backend-file","id":"memvirtiomem0","mem-path":"/dev/hugepages/libvirt/qemu/5-avocado-vt-vm1","reserve":false,"size":2147483648} -device {"driver":"virtio-mem-ccw","block-size":1048576,"requested-size":2147483648,"memdev":"memvirtiomem0","id":"virtiomem0","devno":"fe.0.0009"} ...
3. Check the hugepage usage

# virsh freepages --all
Node 0:
4KiB: 5102353
1024KiB: 1746

Expected results

The preallocation and allocation threads should be seen in qemu cmdline, and there should be no 1M hugepage left after starting the guest(virtio-mem related 2G hugepages should be allocated).

Actual results

The preallocation and allocation threads are not seen in qemu cmdline, and there stil 1746 hugepages are not allocated.