1. A method of direct storage device sharing in a virtualized environment, comprising: a storage controller assigning each of a plurality of virtual functions of a plurality of guests an associated memory area of a physical memory, including at a first boot of one of the guests, the storage controller receiving a request from the one of the guests, said request including an authentication key, and in response to the request, triggering an interrupt of a physical function to a hypervisor; and the storage controller receiving from the hypervisor a configuration command over the physical function, the configuration command setting up hardware in the storage controller to allocate storage in the storage device for said one of the guests and to provide a mapping function for the authentication key to provide the one of the guests with access to a specified storage area in the storage device; and the storage controller executing the virtual functions in a single root-input/output virtualization environment to provide each of a plurality of guests with direct access to the physical memory, including for a subsequent boot of the one of the guests, after said first boot, the storage controller receiving a subsequent request from the one of the guests, said subsequent request including the authentication key, and the storage controller setting up a mapping function for the authentication key, without intervention of the hypervisor during said subsequent boot, to provide said one of the guests with direct access only to the specified storage area in the storage device set up for the authentication key.