Function pmap_mapbios

freebsd/arm64/arm64/pmap.c:5871–5976

}

void *
pmap_mapbios(vm_paddr_t pa, vm_size_t size)
{
	struct pmap_preinit_mapping *ppim;
	vm_offset_t va, offset;
	pd_entry_t *pde;
	pt_entry_t *l2;
	int i, lvl, l2_blocks, free_l2_count, start_idx;

	if (!vm_initialized) {
		/*
		 * No L3 ptables so map entire L2 blocks where start VA is:
		 * 	preinit_map_va + start_idx * L2_SIZE
		 * There may be duplicate mappings (multiple VA -> same PA) but
		 * ARM64 dcache is always PIPT so that's acceptable.
		 */
		 if (size == 0)
			 return (NULL);

		 /* Calculate how many L2 blocks are needed for the mapping */
		l2_blocks = (roundup2(pa + size, L2_SIZE) -
		    rounddown2(pa, L2_SIZE)) >> L2_SHIFT;

		offset = pa & L2_OFFSET;

		if (preinit_map_va == 0)
			return (NULL);

		/* Map 2MiB L2 blocks from reserved VA space */

		free_l2_count = 0;
		start_idx = -1;
		/* Find enough free contiguous VA space */
		for (i = 0; i < PMAP_PREINIT_MAPPING_COUNT; i++) {
			ppim = pmap_preinit_mapping + i;
			if (free_l2_count > 0 && ppim->pa != 0) {
				/* Not enough space here */
				free_l2_count = 0;
				start_idx = -1;
				continue;
			}

			if (ppim->pa == 0) {
				/* Free L2 block */
				if (start_idx == -1)
					start_idx = i;
				free_l2_count++;
				if (free_l2_count == l2_blocks)
					break;
			}
		}
		if (free_l2_count != l2_blocks)
			panic("%s: too many preinit mappings", __func__);

		va = preinit_map_va + (start_idx * L2_SIZE);
		for (i = start_idx; i < start_idx + l2_blocks; i++) {
			/* Mark entries as allocated */
			ppim = pmap_preinit_mapping + i;