AMD : BSOD unsupported processor since Windows build 26100.4202+ ( update kb5060842 + its preview kb5058499 )

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KciNicK

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May 27, 2024
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after installing this update on windows 11, vms fail on start with BSOD unsupported processor, using "host" as cpu type, walkaround changing to "x86-64-v4", does anyone having the same issue?
 
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Same thing. Switched to x86-64-v4 like you mentioned and Windows 11 starts and completes the update.
 
This happened to me on a few laptops that I have that run KVM/QEMU. On an AMD based laptop, I had to change the CPU architecture from host to EPYC-V4 to get Windows 11 to boot and finish the updates.

Looks like a Windows bug on AMD CPUs. I have two Dell XPS13 9310 with 11th gen i5 procs and those updated and rebooted just fine.
 
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This looks like a Windows bug that affects KVM/QEMU with AMD CPUs. It does not seem to be specific to Proxmox.
 
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Not reproducible on Win10 22H2 neither Win11 23H2 (each with their Preview Update Late May 2025 )
Only with Preview Windows Update Late May 2025 for 26100 build ( used by Windows 11 24H2 and Windows Server 2025 )
 
I've hit the same issue with my test Win11 24H2 VM (host is an AMD 5950X) - I was eventually able to get it booting by changing the CPU to EPYC, as apparently that's a better fit for Zen3 CPUs than the X86-64 ones which are more tuned to Intel. No idea if that's really true but it works for me.

Oddly, none of my 6 Win2025 servers are offering this preview which they normally would.
 
reproducible with today cumulative June 2025 update.
Windows 11 24H2 + Windows Server 2025.
BSOD unsupported processor if cpu type is "host" ( AMD EPYC 7302 release date mid-2019 + PVE 8.4 Kernel 6.8.12-9 )
 
reproducible on "Ryzen5 PRO 4650GE" (~Zen2) / PVE 8.2.2 / PVE-QEMU 9.0 / Kernel 6.8.4-2
by the way I use mitigations=off on both systems.
Cumulative Windows Update June 2025 is kb5060842 for both Windows 11 24H2 and Windows Serveur 2025.
cpu type "host" can't be used.
 
I noted this today with Server 2025, though core only!! server 2025 gui didn't appear to have this issue? Changing the core machines to EPYC Genoa works fine for the core machines. the server is an AMD EPYC 9654 96-Core Processor. as a test, I rolled back one core machine to before the update and it works fine on host as the processor setting, as soon as I applied the update again... same issue, Processor not supported.
 
BSOD "unsupported processor" just happened to me on a Windows 11 24H2 VM while trying to do the Windows Update discussed here...

proxmox 8.4.1 with kernel 6.14, Ryzen 7 5700X

changed the processor type from host to x86-64-v3 and it works for now
 
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