Knowledge Base

VMware

Windows Performance

VMware have started moving away from their own low level hypervisor monitor (CPL0) and are supporting "user level monitors" (ULM) such as Apple Virtualization Framework on macOS and the Windows Hyper-V hypervisor. The work to transition the Linux version to use Linux kernel KVM is also underway.

On Windows in ULM mode the performance of VMs is affected and has seen to be slower. ULM mode on Windows and macOS also mea certina hacks such as CPUID masks do not work reliably, if at all.

There is a long and good thread at Broadcom which discusses the options.

https://community.broadcom.com/vmware-cloud-foundation/discussion/disabling-hyper-v-hypervisor-on-windows-11-pro-host-to-get-vmware-17s-cpl0-vs-ulm-monitor-mode

Stability

During testing I have found that 25H2 on Linux is particularly unstable especially with Wayland based desktop environments. VMware have acknowledged these issues. For the best environment I rolled back to Ubuntu 24.04 LTS and Workstation 17.6.4 and have not had any issues with it.

This seems to have been resolved with 25H2u1 (25.0.1)

Broadcom's list of supported host OS is here. https://knowledge.broadcom.com/external/article?legacyId=80807

25H2 Crash

There is a VMware bug that is not directly related to OC4VM but has been seen when running a macOS VM.

If you look in the vmware.log file you will see a message:

Third party host clock rate has already been set

Apparently this is a known issue at Broadcom, https://techdocs.broadcom.com/us/en/vmware-cis/desktop-hypervisors/workstation-pro/25H2/release-notes/vmware-workstation-pro-25h2-release-notes.html.

(From https://www.reddit.com/r/vmware/comments/1obdvqh/error_occur_after_vmware_25h2_update/)

To fix it add this line to the VMX file:

mks.enableVulkanPresentation = "FALSE"