[Solved] Virtual machine crashes system after kernel update

[vs87]

Hi guys,
I had the same problem after kernel update (18.3 Cinnamon), so I upgraded VirtualBox to 5.2 from their repo (virtualbox-5.2 | 5.2.6-120293~Ubuntu~xenial | https://download.virtualbox.org/virtualbox/debian xenial/contrib amd64 Packages)
The problem is gone, but after upgrading (even with a bare new VM / guest OS installed), I noticed significant performance loss when running my VM (also Mint, the same version) compared to the previous version.
The only difference for me after upgrading to 5.2 was different VirtualBox's UI (not the same as with virtualbox-qt, when installing VirtualBox with Software Manager), but I think it's unlikely because of that. Could it be because of kernel update? I didn't dig to that Meltdown/Spectre issue, but I remember that fixing it will cost you performance loss. Maybe that is the issue, but I'm just guessing. Is there any simple way to troubleshoot (and fix) that performance problem in VirtualBox?
Thanks

[Cosmo.]

The only difference for me after upgrading to 5.2 was different VirtualBox's UI (not the same as with virtualbox-qt, when installing VirtualBox with Software Manager), but I think it's unlikely because of that. Could it be because of kernel update?

No. VB switched completely to Qt5, that gives the difference.

[vs87]

The only difference for me after upgrading to 5.2 was different VirtualBox's UI (not the same as with virtualbox-qt, when installing VirtualBox with Software Manager), but I think it's unlikely because of that. Could it be because of kernel update?

No. VB switched completely to Qt5, that gives the difference.

Do you mean that a newer Qt version is slower than the previous one and the VM itself becomes slower because of that? Is it possible? If so, how they even missed that issue?

[Cosmo.]

Do you mean that a newer Qt version is slower than the previous one and the VM itself becomes slower because of that?

I didn't say that and I do not mean it.