Abstract: In a virtualized computer system in which a plurality of virtual machines run on a platform that includes a hardware graphics processing unit (‘GPU’), provision is made for dynamically assigning the GPU to a selected one of the virtual machines. To this end, each virtual machine comprises, in addition to a guest operating system, a virtual bus with a hot-pluggable slot, and a virtual first configuration-management component responsive to events relevant to the hot-pluggable slot to interact with a second configuration-management component provided as part of the guest operating system of the virtual machine. To assign the GPU to a selected virtual machine, an emulated slot insertion event is generated in respect of the virtual hot-pluggable slot of the selected virtual machine thereby causing the first configuration-management component of that machine to trigger the guest operating system of the first virtual machine to operatively engage with the GPU.