I'm looking at setting up a KVM* virtual machine using a passed through video card for its display. Most mention I've heard of such setups involves having two sets of keyboard, mouse, and monitor, one for the host, and one for the guest. However, I only have one monitor, and while I do have extra keyboards and mice, the keyboard shelf on my desk only really has room for one of each.
The monitor issue is easiest to solve, as my monitor has multiple inputs. Problem solved.
The keyboard and mouse issue is a bit hairier. I have a KVM** switch, and could use it along with USB passthrough, but I'm not sure what happens when both outputs of a KVM** switch are plugged into separate USB ports on the same machine. Does USB passthrough work by port or by device? I rather suspect that the machine will simply see the same keyboard and mouse disconnecting on one USB port and reconnecting on another, and won't be able to have them go to the host when it sees them on one port and to the guest when it sees them on the other. Furthermore, I have another physical machine on the same desk, and would prefer to keep the KVM** switch for multiplexing between the two physical machines, rather than between VMs on one machine.
In cases where virtualization software presents a guest with an emulated display adapter whose output is displayed in a window on the host, there's generally some mechanism whereby clicking in that window redirects mouse and keyboard input to the guest, and then a hotkey returns input focus to the host. Obviously, for VGA passthrough, there's not going to be a window on the host's display adapter to click in, so is there any kind of "Virtual KVM** switch" available for KVM guests with VGA passthrough, whereby a hotkey can switch input focus between the host and guest?
The monitor issue is easiest to solve, as my monitor has multiple inputs. Problem solved.
The keyboard and mouse issue is a bit hairier. I have a KVM** switch, and could use it along with USB passthrough, but I'm not sure what happens when both outputs of a KVM** switch are plugged into separate USB ports on the same machine. Does USB passthrough work by port or by device? I rather suspect that the machine will simply see the same keyboard and mouse disconnecting on one USB port and reconnecting on another, and won't be able to have them go to the host when it sees them on one port and to the guest when it sees them on the other. Furthermore, I have another physical machine on the same desk, and would prefer to keep the KVM** switch for multiplexing between the two physical machines, rather than between VMs on one machine.
In cases where virtualization software presents a guest with an emulated display adapter whose output is displayed in a window on the host, there's generally some mechanism whereby clicking in that window redirects mouse and keyboard input to the guest, and then a hotkey returns input focus to the host. Obviously, for VGA passthrough, there's not going to be a window on the host's display adapter to click in, so is there any kind of "Virtual KVM** switch" available for KVM guests with VGA passthrough, whereby a hotkey can switch input focus between the host and guest?