Does anyone have WS2025 running on a Hyper-V 2019 host? I’ve tried a lot of things and all I have is a boot loop.
Runs fine on vSphere 8. Where exactly does it reset? Have you tried mounting the virtual disk and looking for a memory.dmp or have a look at the event log files if there are any (c:\Windows\System32\winevt\Logs)?
2025 on 2019 HyperV isn’t officialy supported, only on a 2025 host for some reason. Might be VBS and virtual TPM requirements.
Aye, it doesn’t get far enough to write anything to disk. Right after the ‘Loading Files …’ screen reaches 100% it reboots and I get a Hyper-V logo and it loops a few times if I keep pressing ‘any key’, then it shuts off.
I played with everything I could in F8 but nothing helped. I also added a virtual TPM but no change. I built a physical WS2025 host and that’s working OK.
I see that the new WS2025 VMs that I built don’t have a virtual TPM by default and run OK. I like that the default build puts every core in the host in the guest (28 in this case). I can’t tell you how many clients I’ve seen with big beefy servers but every VM has only 1 core assigned. I don’t think my test box will require 28 cores though. 
Sadly, Windows 11 24H2 also does the boot loop dance on Hyper-V 2019. I guess it’s time to do some upgrading… I haven’t been impressed enough with WS2022 to bother.