Abysmal Performance in Fusion 12 after upgrade to macOS Big Sur

[WTell]

After upgrading to macOS Big Sur, performance on my VMs went from great to utterly abysmal. Remedial tasks like opening the Start menu, opening Notepad etc. can now take up to half a minute. Windows are drawn on the screen line-by-line with half second intervals.

The host computer is a 2018 Mac mini with ample memory, disk and CPU. The issue was not present under Fusion 12.0.0 before upgrading to macOS Big Sur. Toggling "Disable Side Channel Mitigations" has no effect.

The attached screenshot shows the vmx processes of three VMs after the VMs have been idling overnight, with no applications open. The VMs (running Windows 10) are pegging the CPU while doing nothing.

[SimonPlusNumber]

Thanks Dieter, I'll try this out on the weekend, and update here with the results.

[mlippold1]

Ok, hopefully some brave soul is willing to upgrade back to Big Sur with a Win10 client with TPM + VBS and try those settings.  I don't have the full day to try it myself.

[bhavik2]

I am having the same issue where the MAC becomes almost unusable due to high CPU due to Fusion. The process is vmware-vmx. I have the side channel mitigation disabled. Is there any workaround or solution

[dieter_stockhau]

bhavik,

did you try this solution: https://communities.vmware.com/t5/VMware-Fusion-Discussions/VMware-Fusion-12-1-0-Big-Sur-Host-Window...

[bhavik2]

I dont see this options in my file

[mysticole928]

Those options don't exist.  You can add them.  However, they do NOT address nested virtualization.  

I was hoping that some of the recent Big Sur updates might address the issue.  They don't.

I did see a comment that Parallels seems to be better.  I am going to try it and see.  Right now using nothing is better than VMware Fusion.

[mlippold1]

I just did the painful restore back to Catalina less than a day after upgrading to Big Sur.   I'm not moving to Big Sur for the foreseeable future until they get it figured out (or until it is time to replace my Mac).

[bhavik2]

Its surprising VMware does not have solution yet for BIG SUR. I hope they have a solution soon . I do not want to roll back as you mentioned its painful

Regards,

Bhavik

[mysticole928]

I thought I'd check, today, to see if there was an update for VMware Fusion.  There was!  I downloaded and installed it.  

There was no change.

WSL2 still does not work.

12.1.2 is the version number I have.

[ColoradoMarmot]

Keep in mind that M1 will never support intel VM's.

[mysticole928]

True.  However, I don't have an M1 MacBook.  

I have an Intel MacBook Pro that ran VMware Fusion 12 without issue using Catalina.  

Big Sur makes VMs that have nested virtualization worthless.

[jeffinmatrix]

I also have this very painful issue. I've tried everything I could but doesn't seem to work. planning to go back to Catalina. 😞

[YC_H]

Below fix works for me running Fusion 12.1.2 and MacBook Pro Intel 7 based on Big Sur:

1. shutdown the VM and close VMWare Fusion.

2. find the VM vmx file, edit the filie with your favour editor and find the "windows.vbs.enabled" line and change it from TRUE to FALSE, if you don't find the line, add it to bottom of the file:

windows.vbs.enabled = "FALSE"

3. open VMWare Fusion but don't start the VM yet, modify the VM setting, under "Processors & Memory", expand "Advance options", uncheck both "Enable hypervisor applications in this virtual machine" and "Enable IOMMU in this virtual machine".

Your are all set.

[mlippold1]

This isn’t a solution for those of us that need VBS and TPM support.

[mysticole928]

To use WSL2, I need to run hypervisor applications.

[bpcoelho]

Hello

After upgrading VMware Fusion Player to 11.1.2 I (re)enabled hypervisor applications and it just works.

BigSur 11.4 

[hal9000mx]

Besides Fusion, Any good Hypervisor that works fine with Big Sur? Anyone?

[DLWKC]

@JasonSimpson Rolling back to VM to Hardware 16 did it for me, thank you!

[jeffinmatrix]

I think I figure out what happened, it is because Apple changed the way of how the process "kernal_task" be triggered. It was used to prevent the cpu to become too hot. However, looks like it doesn't work well on Big Sur.

Basically a laptop cooling pad will solve the issue. However, I found putting a cold gel pad under the MacBook is much better than the laptop cooling pad.

Check this: https://andyinmatrix.blogspot.com/2021/08/fix-macbook-big-sur-slowness.html