void __init arm64_memblock_init()

in mm/init.c [192:319]

• 61 lines of code
• 19 McCabe index (conditional complexity)

void __init arm64_memblock_init(void)
{
	s64 linear_region_size = PAGE_END - _PAGE_OFFSET(vabits_actual);

	/*
	 * Corner case: 52-bit VA capable systems running KVM in nVHE mode may
	 * be limited in their ability to support a linear map that exceeds 51
	 * bits of VA space, depending on the placement of the ID map. Given
	 * that the placement of the ID map may be randomized, let's simply
	 * limit the kernel's linear map to 51 bits as well if we detect this
	 * configuration.
	 */
	if (IS_ENABLED(CONFIG_KVM) && vabits_actual == 52 &&
	    is_hyp_mode_available() && !is_kernel_in_hyp_mode()) {
		pr_info("Capping linear region to 51 bits for KVM in nVHE mode on LVA capable hardware.\n");
		linear_region_size = min_t(u64, linear_region_size, BIT(51));
	}

	/* Remove memory above our supported physical address size */
	memblock_remove(1ULL << PHYS_MASK_SHIFT, ULLONG_MAX);

	/*
	 * Select a suitable value for the base of physical memory.
	 */
	memstart_addr = round_down(memblock_start_of_DRAM(),
				   ARM64_MEMSTART_ALIGN);

	if ((memblock_end_of_DRAM() - memstart_addr) > linear_region_size)
		pr_warn("Memory doesn't fit in the linear mapping, VA_BITS too small\n");

	/*
	 * Remove the memory that we will not be able to cover with the
	 * linear mapping. Take care not to clip the kernel which may be
	 * high in memory.
	 */
	memblock_remove(max_t(u64, memstart_addr + linear_region_size,
			__pa_symbol(_end)), ULLONG_MAX);
	if (memstart_addr + linear_region_size < memblock_end_of_DRAM()) {
		/* ensure that memstart_addr remains sufficiently aligned */
		memstart_addr = round_up(memblock_end_of_DRAM() - linear_region_size,
					 ARM64_MEMSTART_ALIGN);
		memblock_remove(0, memstart_addr);
	}

	/*
	 * If we are running with a 52-bit kernel VA config on a system that
	 * does not support it, we have to place the available physical
	 * memory in the 48-bit addressable part of the linear region, i.e.,
	 * we have to move it upward. Since memstart_addr represents the
	 * physical address of PAGE_OFFSET, we have to *subtract* from it.
	 */
	if (IS_ENABLED(CONFIG_ARM64_VA_BITS_52) && (vabits_actual != 52))
		memstart_addr -= _PAGE_OFFSET(48) - _PAGE_OFFSET(52);

	/*
	 * Apply the memory limit if it was set. Since the kernel may be loaded
	 * high up in memory, add back the kernel region that must be accessible
	 * via the linear mapping.
	 */
	if (memory_limit != PHYS_ADDR_MAX) {
		memblock_mem_limit_remove_map(memory_limit);
		memblock_add(__pa_symbol(_text), (u64)(_end - _text));
	}

	if (IS_ENABLED(CONFIG_BLK_DEV_INITRD) && phys_initrd_size) {
		/*
		 * Add back the memory we just removed if it results in the
		 * initrd to become inaccessible via the linear mapping.
		 * Otherwise, this is a no-op
		 */
		u64 base = phys_initrd_start & PAGE_MASK;
		u64 size = PAGE_ALIGN(phys_initrd_start + phys_initrd_size) - base;

		/*
		 * We can only add back the initrd memory if we don't end up
		 * with more memory than we can address via the linear mapping.
		 * It is up to the bootloader to position the kernel and the
		 * initrd reasonably close to each other (i.e., within 32 GB of
		 * each other) so that all granule/#levels combinations can
		 * always access both.
		 */
		if (WARN(base < memblock_start_of_DRAM() ||
			 base + size > memblock_start_of_DRAM() +
				       linear_region_size,
			"initrd not fully accessible via the linear mapping -- please check your bootloader ...\n")) {
			phys_initrd_size = 0;
		} else {
			memblock_remove(base, size); /* clear MEMBLOCK_ flags */
			memblock_add(base, size);
			memblock_reserve(base, size);
		}
	}

	if (IS_ENABLED(CONFIG_RANDOMIZE_BASE)) {
		extern u16 memstart_offset_seed;
		u64 mmfr0 = read_cpuid(ID_AA64MMFR0_EL1);
		int parange = cpuid_feature_extract_unsigned_field(
					mmfr0, ID_AA64MMFR0_PARANGE_SHIFT);
		s64 range = linear_region_size -
			    BIT(id_aa64mmfr0_parange_to_phys_shift(parange));

		/*
		 * If the size of the linear region exceeds, by a sufficient
		 * margin, the size of the region that the physical memory can
		 * span, randomize the linear region as well.
		 */
		if (memstart_offset_seed > 0 && range >= (s64)ARM64_MEMSTART_ALIGN) {
			range /= ARM64_MEMSTART_ALIGN;
			memstart_addr -= ARM64_MEMSTART_ALIGN *
					 ((range * memstart_offset_seed) >> 16);
		}
	}

	/*
	 * Register the kernel text, kernel data, initrd, and initial
	 * pagetables with memblock.
	 */
	memblock_reserve(__pa_symbol(_stext), _end - _stext);
	if (IS_ENABLED(CONFIG_BLK_DEV_INITRD) && phys_initrd_size) {
		/* the generic initrd code expects virtual addresses */
		initrd_start = __phys_to_virt(phys_initrd_start);
		initrd_end = initrd_start + phys_initrd_size;
	}

	early_init_fdt_scan_reserved_mem();

	high_memory = __va(memblock_end_of_DRAM() - 1) + 1;
}