A shot in the dark, I’ve only seen “piix4” errors as non-critical errors (but very common). This has been discussed in the bugzilla, but I think maintainers have been reluctant to make changes because a guy in the Ubuntu world who did some research and published his results a year and a half ago seems to have disappeared leaving a number of underlying unanswerable questions…
I still am not sure whether that error is really a kernelspace error, I don’t see enough info to offer an analysis.
But, if you’d like to try this script I’ve created (or do the steps in the script manually), you can blacklist loading that faulty smbus code
https://github.com/putztzu/public_scripts/blob/gh-pages/blacklist_smb.sh
If you can’t boot into the Guest in Emergecy/Recovery mode, then you may need to mount the image from a LiveCD to apply the setting.
Note that in general “piix4” errors occur in <all> paravirtualized Guests, you will see the same error regardless whether you use VBox, VMware, KVM, Xen, etc. but as I described usually the errors are non-critical and usually ignored (just adds some extra seconds to bootup).
I recommend my script be run on every paravirtualized Guest as SOP.
HTH,
TSU