> The general expecation with feature ID registers is that they're 'reset' ^ expectation > exactly once by KVM for the lifetime of a vCPU/VM, such that any > userspace changes to the CPU features / identity are honored after a > vCPU gets reset (e.g. PSCI_ON). > > KVM handles what it calls VM-scoped feature ID registers correctly, but > feature ID registers local to a vCPU (CLIDR_EL1, MPIDR_EL1) get wiped > after every reset. What's especially concerning is that a > potentially-changing MPIDR_EL1 breaks MPIDR compression for indexing > mpidr_data, as the mask of useful bits to build the index could change. > > This is absolutely no good. Avoid resetting vCPU feature ID registers > more than once. Reviewed-by: Sebastian Ott <sebott@xxxxxxxxxx>