Hi Fabrice,
The "hugepages" custom property value in oVirt should be set to size of the pages in KiB (i.e. 1GiB = 1048576, 2MiB = 2048).
In addition, it is recommended to set the huge page size of the VM to the largest size supported by the host.
In the configuration you sent, the huge page size of the VM is set to 64 KiB and since the VM's allocated memory size is at least 32,768 MiB then it requires at least (32768 * 1024/64=) 524,288 pages. Since you only have 120 pages declared in the host then it failed with an error "...there are not enough free huge pages to run the VM".
So to solve the problem, please change the VM's huge page size to be the same as the host's huge page supported size which is 1GiB and therefore hugepages value should be 1048576 KiB instead of 64:
<custom_property>
<name>hugepages</name>
<value>1048576</value>
</custom_property>