It seems that QEMU/KVM's default PS2 mouse and keyboard doesn't work right in most cases. I have especially observed issues using Ctrl+C and Ctrl+V and in Linux you may see repeated key presses in the terminal and you will wonder why you copied something and it's not in the clipboard when you try to paste. The way to temporarily fix it is to press the key that is repeating once(works in Linux but not really in Windows).
Sometimes when moving your mouse it will also s........