Fusion + Big Sur + Side Channel Mitigations

[jailbird]

So I've seen similar posts here, but not this identical one, sadly.

2018 Apple MacBook Pro Retina 15", running latest Big Sur and Fusion Pro 12.1.0.

If I have side channel mitigations enabled, then the VM takes at least 30 seconds to boot, and then it's slow once it does boot.

If I disable side channel mitigations, then the VM refuses to start, I simply get:

"Failed to start the virtual machine".  Sadly no other helpful error.  Under the VM settings->Processors & Memory->Advanced options, all 3 of the "Enable.." options are already unchecked, so that's not it.

This is making Fusion basically unusable for me, sadly.

Sanitized vmware.log is attached.

[ColoradoMarmot]

Known situation, and it's listed in the release notes as I recall.

Side channel mitigations are usually only applicable to large scale environments, not endpoint situations.  Are you worried about malware in the guest escaping (or on the host infecting the guest)?  That's a really sophisticated attack for autonomous code.

[jailbird]

No, but like I said, if I disable them, the VM won't start at all!

[ColoradoMarmot]

I missed that - disabling side channel mitigations shouldn't cause the VM to not start.  That's very strange.  Have you tried removing all the snapshots, and validated that the virtual hardware is at the current version?

[jailbird]

No snapshots, latest HW version.

It happens with every VM, even a brand new one.  It will ONLY start the VM if I enable sidechannel mitigations :(.

[ColoradoMarmot]

That's very strange.  Have you tried a complete clean install?

- drag fusion to the trash

- empty trash

- reboot

- empty trash

- reinstall fusion

[wila]

Hi,

Yes, it is strange that the VM refuses to boot without enabling the Side channel mitigations.
Yet this is not the only user reporting that.

See for example here:
https://communities.vmware.com/t5/VMware-Fusion-Discussions/quot-Failed-to-power-on-quot/m-p/2818539...

That's a VMware employee offering this as a workaround.

--
Wil