Hi there,

Just had to sort out an issue with my Windows 11 VM and thought I would post here in case anyone else encounters it.

My Windows 11 VM (daily use) was fine yesterday. Went to use it this morning and the VM was off. Strange. Restarted and BSOD Unsupported Processor. It has been very stable up until this point.

I had enabled the option Get the latest updates as soon as they're available for Windows Update. Seems like whatever was installed while I was away was the culprit. Luckily, I could reboot into Windows 11 natively (dual boot), which started fine.

The last update installed was: 2025-05 Cumulative Update Preview for Windows 11 Version 24H2 for x64-based Systems (KB5058499)

Examining the packages, included the following:

dism /online /get-packages /format:table | Select-String -Pattern "29/05"

...

Microsoft-Windows-HyperV-OptionalFeature-HypervisorPlatform-Disabled-Package~31bf3856ad364e35~amd64~~10.0.26100.4202 | Installed | Feature Pack | 29/05/2025 1:58 PM

Searching that indicated this disables Hyper-V/VM features. Sure, enough going to the Add/Remove Windows Features revealed both Virtual Machine Platform and Windows Hypervisor Platform options had been turned off. Turned them back on, rebooted back into Unraid and restarted the VM - back to normal!

Seems strange for an update to disable a feature in use? Maybe the cause was something else, yet the above steps got me back on track. Anyone else encounter this, or similar with another Windows 11 update?

Hoping it doesn't occur again! In the meantime, turned off the Get the latest option - at least for a while.

Xav.

I'm was having this same issue. After installing KB5058499, my VM crashed and BSOD stated Unsupported_Processor. In Unraid, I had to deselect all pinned CPU cores and restart the VM. Once restarting, I noticed the VM was extremely slow.

I uninstalled the update and relogged in. I noticed that the VM was still slow, so I edited the Unraid VM settings and pinned CPU cores to the VM. Once I did that, the VM returned to normal operation.

Just for giggles, I reinstalled the update, but this time with no CPU cores pinned, and the update completed successfully, but system seemed unstable. Enabled Virtual Machine Platform, repinned CPU cores, and the VM was stable again, with KB5058499 installed.

I didn't have any Hyper-V features or Virtual Machine Platform enabled previous to the update and everything was working fine.

Thanks you so much, this post save my day.

I pined only one core to the Windows 11 VM and then the VM is able to start. After the boot I enable Virtual Machine Platform and Windows Hypervisor Platform options and shutdown the VM.

I enabled the cores again and now the Windows 11 run as before.

Thank you xavierda

OMGGGG thanks all for the tips. I just installed the update on my Win 11 VM and was upset to be greeted with a BSOD.

Removing the CPU pinning (the new "deselect all" button in the Unraid VM template editor) allowed the update to finish installing and then boot into Windows.

Doing anything was painfully slow with the single core CPU, so I tried re-enabling multiple cores, only to be greeted with the BSOD again.

So I used the following instructions to enable the Virtual Machine Platform option mentioned above.

FWIW I didn't need to enable the Windows Hypervisor Platform option, as I believe it's for running VMs in Windows, not running Windows as a VM.

Thanks again, all, for your info: I was sure this was going to take all day to get working...

For me windows after a few reboots uninstalled the update itself and is no longer an option for me. It just says update unsuccessful! Was getting worried for a minute. Why would Microsoft do that...??

I was having the same issue, and it took me a couple of days to figure out how to fix it. After unpinning all my cores, allowing the update to be installed, enabling the Virtual Machine Platform in Windows Features, shutting down the VM, repinning the cores, and starting up the VM. Everything is working back to normal! I created a Snapshot before and after the changes, just in case I needed to go back. Thank you so much for help!

thanks guys, this helped me as well.

Had the same issue. Took me a long time to resolve it properly.

Weirdly, I can't boot into Windows if I have <hyperv mode='passthrough'> specified - I will still get the Unsupported Processor error in this case.
This never used to happen.

It appears to have negatively impacted gaming performance for me.

Dang I have been dealing with this for AGES. Thanks! I'll need to bake the hypervisor settings into my AutoInstall windows 11 ISO.

Edit: If you use an autounattend.xml you need to add this to the system context, before first login:

$ConfirmPreference = 'None'

Enable-WindowsOptionalFeature -Online -FeatureName VirtualMachinePlatform -All -NoRestart

$ConfirmPreference = 'High'

It should do an automatic restart anyways for the other autounattend.

Edited June 14, 20251 yr by Jclendineng

Just wondering - can anyone else confirm if <hyperv mode='passthrough'> works for them after this update?
I'm running a Ryzen 5 5950x.

1 hour ago, ross232 said:

Just wondering - can anyone else confirm if <hyperv mode='passthrough'> works for them after this update?
I'm running a Ryzen 5 5950x.

no issues here

but hyper-v is custom here

<hyperv mode='custom'>

<relaxed state='on'/>

<vapic state='on'/>

<spinlocks state='on' retries='8191'/>

<vpindex state='on'/>

<synic state='on'/>

<stimer state='on'/>

<vendor_id state='on' value='none'/>

</hyperv>

1 hour ago, alturismo said:

no issues here

but hyper-v is custom here

<hyperv mode='custom'>

<relaxed state='on'/>

<vapic state='on'/>

<spinlocks state='on' retries='8191'/>

<vpindex state='on'/>

<synic state='on'/>

<stimer state='on'/>

<vendor_id state='on' value='none'/>

</hyperv>

Thanks, but I'm talking about Hyper-V passthrough specifically. CPU passthrough still works for me.

3 hours ago, ross232 said:

Thanks, but I'm talking about Hyper-V passthrough specifically. CPU passthrough still works for me.

thought so, but i cant confirm

On 6/14/2025 at 9:11 AM, ross232 said:

It appears to have negatively impacted gaming performance for me.

here its fine without this ... actually cant imagine what impact this should have.

before with an 3080to, now with a 5080 ... im almost on bare metal level ... and no stuttering or so ...

Passing some info from another website but similar problem. Adding this line to the CPU section fixed my problems that were still arising post-update and the booting.

<cpu>

<feature policy='disable' name='arch-capabilities'/>

</cpu>

May want to disable TPM, according to your situation, by deleting the following:

<tpm model='tpm-tis'>

<backend type='emulator' version='2.0' persistent_state='yes'/>

</tpm>

Edited June 15, 20251 yr by geekunraid

Thanks @alturismo and @geekunraid for your help, really appreciate both of your replies.

@geekunraid looks like that setting did the trick! Thank you so much

I have the following settings working perfectly again now on my Ryzen 5950X:

<features>

<acpi/>

<apic eoi='off'/>

<hyperv mode='passthrough'>

</hyperv>

<kvm>

<hidden state='on'/>

</kvm>

<vmport state='off'/>

<ioapic driver='kvm'/>

</features>

<cpu mode='host-passthrough' check='none' migratable='off'>

<topology sockets='1' dies='1' clusters='1' cores='[SETME]' threads='[SETME]'/>

<cache mode='passthrough'/>

<feature policy='require' name='x2apic'/>

<feature policy='require' name='tsc-deadline'/>

<feature policy='require' name='hypervisor'/>

<feature policy='require' name='tsc_adjust'/>

<feature policy='disable' name='arch-capabilities'/>

<feature policy='require' name='cmp_legacy'/>

<feature policy='require' name='perfctr_core'/>

<feature policy='require' name='virt-ssbd'/>

<feature policy='disable' name='monitor'/>

<feature policy='disable' name='svm'/>

<feature policy='require' name='topoext'/>

</cpu>

<clock offset='localtime'>

<timer name='rtc' tickpolicy='catchup'/>

<timer name='pit' tickpolicy='delay'/>

<timer name='tsc' present='yes' tickpolicy='merge' mode='native'/>

<timer name='hypervclock' present='yes'/>

</clock>

And

<qemu:commandline>

<qemu:arg value='-fw_cfg'/>

<qemu:arg value='opt/ovmf/X-PciMmio64Mb,string=65536'/>

<qemu:arg value='-overcommit'/>

<qemu:arg value='cpu-pm=off'/>

<qemu:arg value='-global'/>

<qemu:arg value='q35-pcihost.pci-hole64-size=2048G'/>

<qemu:arg value='-machine'/>

<qemu:arg value='max-ram-below-4g=4G'/>

</qemu:commandline>

Edited June 16, 20251 yr by ross232

FYI I took what you posted and ran some tests, I don't know about pass thru (I dint use that) but for the UNSUPPORTED_PROCESSOR BSOD on initial install, you only need to add 1 feature under topoext:

<feature policy='require' name='topoext'/>

<feature policy='disable' name='arch-capabilities'/>

Edited June 17, 20251 yr by Jclendineng

On 6/18/2025 at 1:21 AM, Jclendineng said:

FYI I took what you posted and ran some tests, I don't know about pass thru (I dint use that) but for the UNSUPPORTED_PROCESSOR BSOD on initial install, you only need to add 1 feature under topoext:

<feature policy='require' name='topoext'/>

<feature policy='disable' name='arch-capabilities'/>

This was all I needed, thanks!

On 6/17/2025 at 11:21 AM, Jclendineng said:

FYI I took what you posted and ran some tests, I don't know about pass thru (I dint use that) but for the UNSUPPORTED_PROCESSOR BSOD on initial install, you only need to add 1 feature under topoext:

<feature policy='require' name='topoext'/>

<feature policy='disable' name='arch-capabilities'/>

This definitely helped me also. It wasn't an initial install though, an old faithful install. Once I was able to get it booted it uninstalled the bad update. Thank you for your help!!

Unfortunately this makes the VM dog slow. Looking for a better solution, but it takes 10x longer to install than previous versions.

So what is the prefered solution? Enable Virtual Machine in Windows or disable arch-capabilities in the VM definition?

Hi all,

Glad the original post was helpful. I had to rebuild my XML file after a crash - for some unknown reason. Main driver was to be able to play Fortnite again.

Here's the main bit of my XML for the VM.

I don't explicitly hide the VM, it seems the smbios mode = host does the trick to get pass EasyCheet, and I get better performance.

<os>

<smbios mode='host'/>

</os>

<features>

<acpi/>

<apic/>

<hyperv mode='custom'>

<relaxed state='on'/>

<vapic state='on'/>

<spinlocks state='on' retries='8191'/>

<vpindex state='on'/>

<synic state='on'/>

<stimer state='on'/>

<vendor_id state='on' value='none'/>

</hyperv>

<vmport state='off'/>

</features>

<cpu mode='host-passthrough' check='none' migratable='off'>

<topology sockets='1' dies='1' clusters='1' cores='14' threads='2'/>

<cache mode='passthrough'/>

<feature policy='require' name='topoext'/>

<feature policy='disable' name='hypervisor'/>

</cpu>

<clock offset='localtime'>

<timer name='hpet' present='no'/>

<timer name='hypervclock' present='yes'/>

</clock>

<on_poweroff>destroy</on_poweroff>

<on_reboot>restart</on_reboot>

<on_crash>restart</on_crash>

No BSOD.

Xav,

FYI Windows 11 VM creation still 100% broken by default in latest version.

FYI

Just on a whim I downloaded Windows 11 Dev Build 26120 using UUPDump and created an autounattend.xml for it and it works, so the issue appears to have been Microsoft being Microsoft and breaking stuff in stable again, so kinda like every patch Tuesday.

On 7/6/2025 at 1:39 AM, xavierda said:

I don't explicitly hide the VM, it seems the smbios mode = host does the trick to get pass EasyCheet, and I get better performance.

Hey thanks for this! Been expirementing with different combinations of smbios mode = host, feature policy='disable' name='hypervisor', and kvm disabled. On my setup at least I get much better cpu limited performance without disabling hypervisor. Going from ~120 fps to ~200 fps with 7 x3d cores of my 7950x3d passed through to the vm in 1080p cyberpunk high. Might be different for you, but thought I'd share this in case it helps someone. I'm still able to get past the SM2 EAC vm check.

Edited August 6, 2025Aug 6 by fadynakhla