HV_HYPERCALL_REP_START_OFFSET
hc.rep_idx = (hc.param >> HV_HYPERCALL_REP_START_OFFSET) & 0xfff;
control |= (u64)rep_start << HV_HYPERCALL_REP_START_OFFSET;
control |= (u64)rep_comp << HV_HYPERCALL_REP_START_OFFSET;