Function pmap_update_entry

freebsd/arm64/arm64/pmap.c:3439–3467

* Performs a break-before-make update of a pmap entry. This is needed when * either promoting or demoting pages to ensure the TLB doesn't get into an * inconsistent state. */

 * inconsistent state.
 */
static void
pmap_update_entry(pmap_t pmap, pd_entry_t *pte, pd_entry_t newpte,
    vm_offset_t va, vm_size_t size)
{
	register_t intr;

	PMAP_LOCK_ASSERT(pmap, MA_OWNED);

	/*
	 * Ensure we don't get switched out with the page table in an
	 * inconsistent state. We also need to ensure no interrupts fire
	 * as they may make use of an address we are about to invalidate.
	 */
	intr = intr_disable();

	/*
	 * Clear the old mapping's valid bit, but leave the rest of the entry
	 * unchanged, so that a lockless, concurrent pmap_kextract() can still
	 * lookup the physical address.
	 */
	pmap_clear_bits(pte, ATTR_DESCR_VALID);
	pmap_invalidate_range(pmap, va, va + size);

	/* Create the new mapping */
	pmap_store(pte, newpte);
	dsb(ishst);

	intr_restore(intr);
}

#if VM_NRESERVLEVEL > 0
/*