virtualbox.org

VirtualBox 6.1
host: Kubuntu 20.04.2
guest: Windows 10 pro

Sometimes happens that keyboard is not captured by the virtual machine. This lag is temporary and usually lasts less than minutes.

How can I fix it?

The keyboard doesn't need to be "captured" by a VM. The host should always own it. The VirtualBox app gets keystroke events from the host OS just like any other host app. You don't need to do anything special.

I.e. if you installed a USB filter to steal ownership of the keyboard from the host then you need to remove that. Likewise if you created a USB filter that could be grabbing the keyboard then you need to change the filter specs to stop that happening. A host PC with no keyboard (or mouse) will be hard to use.

mpack wrote:The keyboard doesn't need to be "captured" by a VM.

Keyboard is a PS2 one, not USB. On the host machine keyboard works fine, on the guest machine it take few minutes (after complete boot of the vm) before I can digit anything

Then it doesn't sound like you have a keyboard problem at all. It sounds like something in the guest is eating CPU.

There is no process in VirtualBox that can stop the host OS from registering PS/2 keystrokes.