Ram in guest VM differs from configured in Qemu/Libvirt

[Gesiel Galvão Bernardes]

Hi, I noticed that when I use the "hot-add memory" resource, the guest VMs is decreased 360MB of the RAM available to use. If the RAM value is fixed, the problem does not occours. This is independent of the amount of RAM, For example:

Guest 1:
   <memory unit='KiB'>16777216</memory>
  <currentMemory unit='KiB'>1048576</currentMemory>
 Disponible in guest (free -m): 649MB

Guest 2:
  <memory unit='KiB'>16777216</memory>
  <currentMemory unit='KiB'>8388608</currentMemory>
  Disponible in guest (free -m): 7817MB

Guest 3:
  <memory unit='KiB'>8392704</memory>
  <currentMemory unit='KiB'>8392704</currentMemory>
  Disponible in guest (free -m): 7962MB

I using:
- Qemu-KVM 6.2
- Libvirt 8.0.0
- Rocky Linux 8.5

Can anyone tell me why this happens?


Regards,
Gesiel