I updated the Ubuntu kernel today and everything seems to be going well. But when Trying to open a Previously created Windows 8.1 virtual machine inside VirtualBox, an error was reported:

Feeling confused, hard to create a virtual machine so can not be used?
After a long look, it turns out that the kernel driver for VirtualBox was not loaded successfully, presumably because the kernel had just been upgraded.
The solution is simple: simply execute the following command:

sudo /etc/init.d/vboxdrv setup

At this point, the VirtualBox kernel driver will be recompiled and loaded, possibly waiting a while.
After the command is executed, try to open the virtual machine again, and everything is fine.