[SOLVED] How I fixed 100 % host CPU usage (Windows 11 24H2 guest)

[gothbert]

Dear all,

after updating VM guest to Windows 11 Pro 24H2 and changing some settings, the host (Xeon E3-1230 v3) had a 100 % load on all cores assigned to the VM. There are quite a lot of similar reports on that issue in this and other forums.

I managed to solve the issue as follows:

• Turn off core isolation in the Windows 11 security settings

The following measures, which did or did not help other users, did not work for me:

• Do not use memory ballooning but assign a fixed amount of memory.
• Turn VirtIO IOMMU on or off.
• Assign only the real amount of cores to the VM (i.e. 4 instead of 8 on a hyperthreading CPU)
• Change CPU type from "host" to "KVM64" (results in Win11 boot loop)
• Use latest VirtIO drivers (0.1.266).

Hope this helps those who encounter the same issue.

Best regards,
Boris