PID_SHIFT
#define VERSION_SHIFT (PID_SHIFT + PID_BITS)
#define CTX_PID(c) (((c) >> PID_SHIFT) & PID_MASK)
#define FIRST_CTX ((1UL << VERSION_SHIFT) | (0 << PID_SHIFT))
next_mmu_context += (1UL << PID_SHIFT);