[ovirt-users] Details about bios and custom emulated machine values

Hello, in oVirt 4.3.7 in "Edit VM" -> System -> Advanced parameters I can choose Bios Type: Default Q35 Chipset with Legacy BIOS Q35 Chipset with UEFI BIOS Q35 Chipset with SecureBoot and Custom Emulated Machine: Use cluster default (pc-i440fx-rhel7.6.0) ... q35 pc-q35-rhel7.3.0 pc-q35-rhel7.4.0 pc-q35-rhel7.5.0 pc-q35-rhel7.6.0 and I can apparently mix all possible values. Any deeper information about implications? What is the "Default" value for Bios Type? Did anything change in 4.3.8 (eg official support for q35)? I search also through official docs for RHV 4.3 (virtual mgmt guide, appendix A), but for example I don't find any reference to the "Bios Type" parameter and a vague reference to the "Custom Emulated Machine". Is there any more detailed link? Thanks, Gianluca