This message usually does not mean the hypervisor is still running. It means Windows tried to start VSM because a virtualization-based security component is still configured, but AMD virtualization was disabled in UEFI, so the check failed.
Here are some suggestions you can try:
Press Windows key + R, enter msinfo32, and check Virtualization-based security. If it says Not enabled and there is no “hypervisor detected” message, the hypervisor is already off. The Event Viewer entry can be ignored.
Open Turn Windows features on or off and clear any enabled items named Virtual Machine Platform, Windows Hypervisor Platform, Windows Sandbox, and Windows Subsystem for Linux. Restart afterward.
Open Terminal as administrator and run:
bcdedit /set hypervisorlaunchtype off
bcdedit /set vsmlaunchtype off
Then perform a full shutdown, not only a restart:
shutdown /s /t 0
Install the latest BIOS and AMD chipset driver from the PC or motherboard manufacturer. Firmware settings can affect whether Windows correctly detects AMD-V and IOMMU.
Build 26200.9278 is also from the KB5120998 preview update. Since no matching known issue is currently listed, avoid deleting VBS policy files or additional protected system files.
Thank you for your patience in reading, I hope this information has been helpful to you.
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