topic Re: Poor performance after update with message about side channel mitigation in VMware Workstation Player Discussions

Poor performance after update with message about side channel mitigation

Mentyth — Fri, 20 Nov 2020 19:11:34 GMT

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.

Re: Poor performance after update with message about side channel mitigation

bluefirestorm — Fri, 20 Nov 2020 20:10:05 GMT

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"

Re: Poor performance after update with message about side channel mitigation

RobSentel — Wed, 08 Sep 2021 13:30:31 GMT

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,

Re: Poor performance after update with message about side channel mitigation

RaSystemlord — Wed, 08 Sep 2021 17:55:28 GMT

@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.

Re: Poor performance after update with message about side channel mitigation

RobSentel — Wed, 08 Sep 2021 19:56:21 GMT

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

Re: Poor performance after update with message about side channel mitigation

AustinCat — Thu, 02 Jun 2022 21:49:52 GMT

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>

Re: Poor performance after update with message about side channel mitigation

Technogeezer — Fri, 03 Jun 2022 02:15:42 GMT

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.

Re: Poor performance after update with message about side channel mitigation

MisterEd51 — Wed, 25 Jan 2023 23:22:29 GMT

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"

Re: Poor performance after update with message about side channel mitigation

JMATEUS — Wed, 11 Oct 2023 17:41:38 GMT

I did insert the statment ulm.disableMitigations="TRUE" in the vmx file to disable side channel mitigations as instructed because of the very low performance, the warning message disapeared at machine start but the performance stays very poor like before.
Operating System Windows 11 22H2 last update
VMWARE version 17.0.2 build-21581411

Re: Poor performance after update with message about side channel mitigation

Technogeezer — Wed, 11 Oct 2023 20:21:49 GMT

@JMATEUS What cpu are you running on? If it's a 12-gen Intel Core (Alder Lake) or newer that have E-cores and P-cores, you may be seeing Windows not doing a good job of assigning the VM to the more high performance P-cores.

Search the forum as there are a couple of things you can trry that might help you.

Re: Poor performance after update with message about side channel mitigation

JMATEUS — Wed, 11 Oct 2023 20:56:54 GMT

Thank you for your fast response, my cpu is AMD RYZEN 5000 SERIES