,
Side channel methods are techniques that may allow an attacker to gain information through observing the system, such as measuring microarchitectural properties about the system. To prevent this, CPU vendors such as Intel and AMD have developed techniques to mitigate systems’ vulnerability to Side Channel attacks.
But, according to VMware article 79832 Virtual Machines that have side channel mitigations enabled while running on Fusion on Mac OS 11.0 or later or on Workstation on Windows hosts with virtualization based security enabled may run slowly.
For this reason, on systems with Hyper-V enabled, users receive the following warning message when starting a virtual machine in VMware Fusion, Workstation Pro or Workstation Player:
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 for more details.
How to FIX: “You are running this virtual machine with side channel mitigations enabled” in VMware.
As you understand, to remove the above warning message when starting a virtual machine and to fix the performance issues in VMware products, you have to disable the Side Channel mitigations in VMware product you’re using:
How to Disable Side Channel mitigations on VMware Fusion:
1. Shut down the Virtual Machine.
2. Then open the Virtual Machine’s Settings and click Advanced.
3. Check “Disable Side Channel Mitigations”
How to Disable Side Channel mitigations on Workstation Pro:
1. Shut down the Virtual Machine.
2. Then open the Virtual Machine’s Settings
3. Select the Options tab and then click Advanced.
4. Check “Disable Side Channel Mitigations for Hyper-V enabled hosts”
How to Disable Side Channel mitigations on Workstation Player:
In VMware Workstation Player there isn’t any option to disable the side channel mitigations in the VM settings, but you can use one of the following methods to do the job:
Method 1. Disable Side Channel Mitigations Globally (in all virtual machines).
If you have set up multiple virtual machines in VMware Workstation Player and want to disable side-channel mitigations on all of them, then proceed and disable all the Hyper-V features on the host machine.*
* Note: If you’re using Hyper-V and don’t want to disable it see the instructions for method-2 below.
1. Press the Windows 
+ R keys to open the RUN command box
2. Type “optionalfeatures” and hit Enter.
3. Here uncheck to disable all the Hyper-V features.
4. When done, click OK to apply the change(s).
6. Restart your computer to apply the change.
Method 2. Disable Side Channel Mitigations for a Specific Virtual Machine in VMware Player.
If you want to disable the side channel mitigations for an single virtual machine in VMware Workstation Player without disabling the Hyper-V features on the host, proceed as follows:
1. Shut down the Virtual Machine.
2. Navigate to the location on disk where the virtual machine’s files are saved:
-
C:Users
DocumentsVirtual MachinesVirtualMachine_Name
3. From View menu click Show and then click to check File name extensions.
4. Open the virtual machine’s WMX file in Notepad.
5. Add the following line in the end of the WMX file.
-
ulm.disableMitigations = “TRUE”
6. Save changes and close Notepad.
7. Start the VM.
That’s it! Let me know if this guide has helped you by leaving your comment about your experience. Please like and share this guide to help others.
