Cache for a multiprocessor system which can treat a local access operation as a shared access operation

A data processing system has several processors 300, 320, 340, each with its own cache 310, 330, 350. Accesses by a processor to its cache may be local or shared. The processor contains a flag 307, which causes a local access to be treated as a global access. The operation may be a clean operation, an invalidate operation or a memory barrier operation issued by an operating system. The flag may be set, when a hypervisor moves a virtual machine from one processor to another. Local operations by the hypervisor may be treated as being local when the flag is set. The cache may be a data cache or a translation look aside buffer.