Poor performance after update with message about side channel mitigation

[Mentyth]

I was asked to upgrade my VM ware player today. I clicked yes and the updater ran and asked for a restart.

This actually completely removed my installed vmware player!!

I downloaded the latest version and installed that but get this  message:

You are running this virtual machine with side channel mitigations enabled. Side channel mitigations provide enhanced security but also lower performance.

To disable mitigations, change the side channel mitigations setting in the advanced panel of the virtual machine settings. Refer to VMware KB article 79832 at  URL for more details.

However the instructions don't say how to do this on vmware player.

[bluefirestorm · Accepted solution]

That message about disabling side channel mitigations shows up only when the ULM is used instead of the ring 0 VMM as the hypervisor monitor. That means the Windows host has been detected to have Hyper-V enabled.

https://blogs.vmware.com/workstation/2020/05/vmware-workstation-now-supports-hyper-v-mode.html

There is no advanced options in VMware Workstation Player. To disable the side channel mitigation, shut down the VM and add the following to the VM vmx configuration file.

ulm.disableMitigations = "TRUE"

[RobSentel]

I updated VMWare Player to 16.

After that the performance decreased until it was impossible to use VMWare.

I tried to adjust the setting by entering the line: ulm.disableMitigations = "TRUE". Did not work, I tried ulm.enableMitigations = "FALSE". NOTHING.

I don't have Hyper-V installed on Windows 10. The problem was solved"????

Performance is poor and makes using VMWare Player impossible.

Perhaps the solution is to roll back the previous version of the software.

The problem was NOT SOLVED, is now a Critical Problem,

[RaSystemlord]

@RobSentel 

I don't know about this Hyper-V issue, but looking for other things.

What is your guest VM and what are you driving there, if meaningful for the slowness to appear? What is your Host hardware? (processor, ram) What is your Windows 10 version (like 2004, or something)? Have you done (or let Microsoft to do) any Feature Upgrade after installing VMware?

Can you share your settings for the VM? 

... this should be in another thread since, as you say, this looks different to the topic of this discussion.

[RobSentel]

The recomendation works: ulm.disableMitigations = "TRUE"

But when I started a VM, the VMWare window freeze.
To unfreeze I need to minimize and maximize the VMWare Window.

After that the performance was ok.
Thanks

[AustinCat]

I'm using macOS Monterey vers 12.4 and the only cmx config file I find (using Finder) is 'Windows 10 and later x64.vmxf'.... is that the one to add 'ulm.disableMitigations = "TRUE" to? I tried but was not able to open VMware Fusion afterwards. Obviously I have no idea what I'm doing and just guessing.

<?xml version="1.0"?>
<Foundry>
<VM>
<VMId type="string">52 d3 13 6f 74 8f d2 90-23 59 3f 2c bb 49 3a d9</VMId>
<ClientMetaData>
<clientMetaDataAttributes/>
<HistoryEventList/></ClientMetaData>
<vmxPathName type="string">Windows 10 and later x64.vmx</vmxPathName></VM><tools-install-info><installError>21009</installError><updateCounter>4</updateCounter></tools-install-info></Foundry>

[Technogeezer]

Wrong file. The instructions were to add the line to the .vmx file, not the vmxf file.  Remove the line from your .vmxf file if it’s still there  

Since you are using Fusion you’ll get a better answer in the VMware Fusion Discussions forum for questions about Fusion as this forum focuses on VMware Workstation on Windows and Linux  

It’s strange why you could not find the .vmx file. It is normally found in the VM’s bundle directory, the same place where your virtual disk files and the .vmxf file are found. 

But you should not have to directly edit the .vmx file to disable side channel mitigations in Fusion 12.x (the only supported version for macOS Monterey 12.x). The setting is in the GUI. Open the VM’s Settings, click on the Advanced settings and you will find a check box to disable side channel mitigations. 

[MisterEd51]

I am running VMWare Workstation 16 Player.

When I run a VM I get a popup warning "You are running the machine with side channel mitigations enabled..."

If I select OK the VM loads very slowly compared to what it used to.

I added the following to the VMs .vmx file:

ulm.disableMitigations = "TRUE"

Now when I try to select or run the VM I get the following error

"Error while opening the virtual machine: VMX file is corrupt."

Since the recommended workaround does not work what should I do about the "side channel mitigations" problem?

Update

After I posted this I realized I must have accidentally corrupted the .vmx file. I didn't know what the problem was so I just recreated the VM. This time when I added thie following again it eliminated the popup message.

ulm.disableMitigations = "TRUE"