memblock

Linux v6.6: mm/memblock.c
Linux v6.6: include/linux/memblock.h
Linux v6.6: arch/arm64/mm/init.c

 * arrays during addition of new regions. This feature should be used
 * with care so that memory allocated for the region array will not
 * overlap with areas that should be reserved, for example initrd.
 *
 * The early architecture setup should tell memblock what the physical
 * memory layout is by using memblock_add() or memblock_add_node()
 * functions. The first function does not assign the region to a NUMA
 * node and it is appropriate for UMA systems. Yet, it is possible to
 * use it on NUMA systems as well and assign the region to a NUMA node
 * later in the setup process using memblock_set_node(). The
 * memblock_add_node() performs such an assignment directly.
 *
 * Once memblock is setup the memory can be allocated using one of the
 * API variants:
 *
 * * memblock_phys_alloc*() - these functions return the **physical**
 *   address of the allocated memory
 * * memblock_alloc*() - these functions return the **virtual** address
 *   of the allocated memory.
 *
 * Note, that both API variants use implicit assumptions about allowed
 * memory ranges and the fallback methods. Consult the documentation
 * of memblock_alloc_internal() and memblock_alloc_range_nid()
 * functions for more elaborate description.
 *
 * As the system boot progresses, the architecture specific mem_init()
 * function frees all the memory to the buddy page allocator.
 *
 * Unless an architecture enables %CONFIG_ARCH_KEEP_MEMBLOCK, the
 * memblock data structures (except "physmem") will be discarded after the
 * system initialization completes.
 */

#ifndef CONFIG_NUMA
struct pglist_data __refdata contig_page_data;
EXPORT_SYMBOL(contig_page_data);
#endif

unsigned long max_low_pfn;
unsigned long min_low_pfn;

unsigned long min_low_pfn;
unsigned long max_pfn;
unsigned long long max_possible_pfn;

static struct memblock_region memblock_memory_init_regions[INIT_MEMBLOCK_MEMORY_REGIONS] __initdata_memblock;
static struct memblock_region memblock_reserved_init_regions[INIT_MEMBLOCK_RESERVED_REGIONS] __initdata_memblock;
#ifdef CONFIG_HAVE_MEMBLOCK_PHYS_MAP
static struct memblock_region memblock_physmem_init_regions[INIT_PHYSMEM_REGIONS];
#endif

struct memblock memblock __initdata_memblock = {
	.memory.regions		= memblock_memory_init_regions,
	.memory.cnt		= 1,	/* empty dummy entry */
	.memory.max		= INIT_MEMBLOCK_MEMORY_REGIONS,
	.memory.name		= "memory",

	.reserved.regions	= memblock_reserved_init_regions,
	.reserved.cnt		= 1,	/* empty dummy entry */
	.reserved.max		= INIT_MEMBLOCK_RESERVED_REGIONS,
	.reserved.name		= "reserved",

	.bottom_up		= false,
	.current_limit		= MEMBLOCK_ALLOC_ANYWHERE,
};

#ifdef CONFIG_HAVE_MEMBLOCK_PHYS_MAP
struct memblock_type physmem = {
	.regions		= memblock_physmem_init_regions,
	.cnt			= 1,	/* empty dummy entry */
	.max			= INIT_PHYSMEM_REGIONS,
	.name			= "physmem",
};
#endif

/*
 * keep a pointer to &memblock.memory in the text section to use it in
 * __next_mem_range() and its helpers.
 *  For architectures that do not keep memblock data after init, this
 * pointer will be reset to NULL at memblock_discard()
 */