Meant to update this again last night - as a road map for those who might try similar at some point:
This community's documentation led me to some relevant information on mouse/keyboard pass-through. Namely, if you want this to work you have to pass the entire PCI controller through to the guest(s), Won't work with motherboard devices.
But I'm out of PCIe slots. What to do...
Simple. Chuck the two serial adapters and install two dual USB 2.0 adapters in their places. Connect the keyboard/mouse to one of the ports and a 4/8/16 port USB to serial adapter to the other. Then pass the entire controller through.
In this particular server (R810) I have 5 available PCIe slots. Two will be used for the video cards, one for a 4x NVMe to PCIe adapter (which is eventually where the VMs will reside) and the remaining two for the USB interfaces. This effectively gives me two discrete physical systems, a third available VM instance (say, for network management, monitoring or whatever) and the XOA instance.
For application/radio control systems hypervisors (nested) I'll probably have 2ea Win11 and whatever flavor of Linux that supports the GT730 GPU on the system - each assigned the pass-through devices - but only two running at any given time. So no resource contention issues.
As far as the displays:
I have the main interface of the server connected via SIP to a 2160AS KVM. I'll take 2 more SIPs and use these as the keyboard/mouse inputs for the USB cards. Video...I use an HDMI active splitter on other systems in the network so I'll employ that here. One of the ports on the add-in GPUs goes to the splitter, one of the splitter outputs goes to the SIP via HDMI to VGA adapter and the other feeds the main ceiling mount monitor. The Primary display will be replicated to the KVM screen. Resolution isn't an issue as I have a video scaler inline with the KVM for just this scenario.
The concept could be expanded. I'm looking at picking up a T630 and building 4 effective "systems" out of it, following the same principle. The 630 has 8 available PCIe slots.
Will update when the next batch of hardware arrives - or I get the Linux side of things sorted. That's next.
