Forum Discussion
Installing Hyper-V on Windows Server 2022 reduces host system CPU to 1 core 1 thread
Got it! My colleague searched and searched for it. And found a workaround!
Ok, the workaround is nasty and shows a problem in how HyperV 2022 in somewhere in the latest Windows Updates communicates with the BIOS and CPU.In the BIOS, go to Advanced -> CPU Configuration -> Advanced Power Management Configuration -> "ENERGY_PERF_BIAS_CFG mode". Edit this option.
You will find six options;
* Extreme Performance (does not work)
* Maximum Performance (does not work)
* Performance (works)
* Balanced Performance (works)
* Balanced Power (works)
* Power (works)See following screenshot as example:
Select one of the working templates and you will get the CPU cores back.
But why?! It looks like there is something wrong with the exposure of the CPU C-states. In this particular situation is looks like it have to do something with CPU masks and with HyperV not accepting/recognizing them:
"Extended Auto-HALT State C1E"Sander.
Hi,
we have the same behavior with one of two servers in a HyperV Failovercluster.
Host1 and Host2 shows all cores/cpu's in Device Manager, but Host1 only runs on one core and one CPU. Also visible in TaskManager.
Reinstalled, new BIOS, reset BIOS, latest updates. Supermicro distributor is trying to help, but no clue...
No difference in hardware and (software) versions.
Sander.
Got it! My colleague searched and searched for it. And found a workaround!
Ok, the workaround is nasty and shows a problem in how HyperV 2022 in somewhere in the latest Windows Updates communicates with the BIOS and CPU.
In the BIOS, go to Advanced -> CPU Configuration -> Advanced Power Management Configuration -> "ENERGY_PERF_BIAS_CFG mode". Edit this option.
You will find six options;
* Extreme Performance (does not work)
* Maximum Performance (does not work)
* Performance (works)
* Balanced Performance (works)
* Balanced Power (works)
* Power (works)
See following screenshot as example:
Select one of the working templates and you will get the CPU cores back.
But why?! It looks like there is something wrong with the exposure of the CPU C-states. In this particular situation is looks like it have to do something with CPU masks and with HyperV not accepting/recognizing them:
"Extended Auto-HALT State C1E"
Sander.
- I don't have the Extreme setting, but changing from Maximum Performance to "just" Performance did indeed fix the issue for me. Thank you, I doubt I'd even attempt that toggle without your post.
- That is interesting, and I'll have a look at my BIOS for sure. For the sake of curiosity, would you mind posting the specs for your two hosts? CPU/motherboard will likely be sufficient. Thanks for posting your findings, and hello again.
