@olivierlambert Well if XCP-NG would really bring what you postulate, it would be great.
But IMHO the truth looks different, at least for me today. HVM templates for Windows usage don't provide PvHVM capability, it is just fully virtualized. Only xenbus drivers are installed, everything else is QEMU fully virtualized, IO & Network, so does burn needless Hypervisor CPU time and power. Looking to this, makes arguments against PVs so called disadvantages on memory access questionable ...
Underlying XenProject stack does provide fully PvHVM capability for Windows in HVM and there are drivers for all of that. "Xen PV Storage Host Adapter", "XENSRC PVDISK SCSI Disk Device", "Xen PV Network Device", "Xen PV Network Class", "Xen PV Console", "Xen PV Bus", on top USB3 capability for HVM. And yes, those Windows (Pv)HVMs are lightning fast, tested with Debian & Ubuntu included XenProject 4.11 stack ...
On top I don't find any installable host agent for Windows HVMs inside XCP-NG, not on WS2019 or WIN10.
So, only Linux guests can be installed as PvHVM, but does that make senses? Every Linux Kernel since version 2.6 brings xen device/driver capabilities, there was never any need to modify any kernel of any known Linux distribution, runable inside a PV. Sure, not all bring XenProject Hypervisor, but that is not the question here.
Killing PV in favor to Linux PvHVM kills Xen's biggest differentiator over other virtualizations, one of its beauties. Xen on ARM is e.g. only possible with good old PV capability ...
I had the plan to restructure my home IT back to my roots, fully open source, happy seeing XenServer as XCP-NG still alive. Great, with an relatively actual kernel, fully 64-bit, UEFI bootable. After testing a while I am rather disenchanted, looking to HVMs for Windows just being fully virtualized, but UEFI capable, and Linux no PV just HVM/PvHVM, not UEFI capable, but what is standard today. Try to to install Ubuntu Server 20.04.2 inside that HVM ...
Not even talking about server managment, ok, good old Windows Center software still available, not ideal, would prefer a sneek HTML5 GUI. XOA looks like vSphere vCenter's ugly sister, bothering permanently with pay options.
Don't get me wrong, I fully understand open source developers cannot live from air and love, but that is absolutely no base to hassle users permanently poking to pay options. And overall the GUI structure is complex and convoluted ... why can't it be easy and good structured like the XCP-NG Center ... ?