The Reasons for poor performance of Windows when the CPU type is host

ucholak said:
can you check if VBS (virtualization based security) is running in host, and not running in x86-64-v3? i think it should be responsible for slowdown
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If you use "host" please remove the nested-virt flag from the CPU to prevent VBS.
VBS is heavily slowing down Windows VMs and can cause issues (even with the v4.
adolfotregosa said:
What VBS ?
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As @ucholak said, Virtualization based security. Basically a windows feature for security. Explained here: https://learn.microsoft.com/en-us/windows-hardware/design/device-experiences/oem-vbs
 
Khensu said:
If you use "host" please remove the nested-virt flag from the CPU to prevent VBS.
VBS is heavily slowing down Windows VMs and can cause issues (even with the v4.

As @ucholak said, Virtualization based security. Basically a windows feature for security. Explained here: https://learn.microsoft.com/en-us/windows-hardware/design/device-experiences/oem-vbs
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I apologize if I wasn't clear, on a Fedora 43 VM? If I provided incorrect information in my previous post, please let me know so I can fix it!
 
adolfotregosa said:
I apologize if I wasn't clear, on a Fedora 43 VM? If I provided incorrect information in my previous post, please let me know so I can fix it!
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Oops, only read the topic about Windows :)
Actually I don't know if Fedora is doing smth similar like VBS xD I doubt it.
Honestly,m now I wonder why "Host" is causing slow downs in Fedora. But we shouldn't keep posting in an old thread like this :) (As it is about Windows)
 
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Khensu said:
Oops, only read the topic about Windows :)
Actually I don't know if Fedora is doing smth similar like VBS xD I doubt it.
Honestly,m now I wonder why "Host" is causing slow downs in Fedora. But we shouldn't keep posting in an old thread like this :) (As it is about Windows)
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Sure, but it's not that old and apparently not exclusive to windows hence me thanking the OP for giving me the idea to try it!
 
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Im not much into windows and do not have a vm currently available, does someone have a comparision between Windows-VM with Host and nested-virt "on" or "+" VS Windows-VM with Host but nested-virt disabled "-"? If not I will do some testing in the next days, but maybe someone already did this and has some insights?

Whats the current best practice regarding having to use vbs in windows: host ? Or does it actually help to have a specific unique cpu-profile? I read the whole post, but its not completly clear whats the current best-practice.
 
jsterr said:
Whats the current best practice regarding having to use vbs in windows: host ?
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Up to Qemu 11, the only option is “Disabled.” Without hardware acceleration, performance will likely drop significantly.

fiona

Post in thread 'QEMU 10.1 available on pve-test and pve-no-subscription as of now'

Hi,
Upstairs_Cycle384 said:
@t.lamprecht enabled MBEC/GMET at the KVM level in

https://git.proxmox.com/?p=pve-kernel.git;a=commit;h=1e810d779b50dd5e7395fa65ad7b3cbf89b910c1

Any chance GMET/MBEC patches from QEMU 11 are getting backported to pve's QEMU 10.x so that his enhancement can be used?

Or is QEMU 11 going to be available for testing soon in any of the pve repos?
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the current plan is to have QEMU 11 be available for the Proxmox VE 9.2 release.
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The test is already available. It’s currently just a working prototype, but official support will require an update to Qemu.

*If you just want to play around, go ahead and try it. If it’s for business purposes, please refrain.

U

Post in thread 'High VM-EXIT and Host CPU usage on idle with Windows Server 2025'

prinskarnatie said:
I'm in a similar situation with Zen5 9955HX. I also had to go the force_avic=Y route. I did add the +hv-avic cpu flag, but propery 8 not showing in the Windows VM .
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Can you post the output of:

dmesg | grep AMD-Vi

Please replace any older CPUs that do not support Windows 11. With the exception of the new CPU, this hardware is not supported. It is not suitable for running the new operating system. Please use it to run earlier versions of the operating system.
 
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