static unsigned long __init get_new_step_size(unsigned long step_size)
{
	/*
	 * Initial mapped size is PMD_SIZE (2M).
	 * We can not set step_size to be PUD_SIZE (1G) yet.
	 * In worse case, when we cross the 1G boundary, and
	 * PG_LEVEL_2M is not set, we will need 1+1+512 pages (2M + 8k)
	 * to map 1G range with PTE. Hence we use one less than the
	 * difference of page table level shifts.
	 *
	 * Don't need to worry about overflow in the top-down case, on 32bit,
	 * when step_size is 0, round_down() returns 0 for start, and that
	 * turns it into 0x100000000ULL.
	 * In the bottom-up case, round_up(x, 0) returns 0 though too, which
	 * needs to be taken into consideration by the code below.
	 */
	return step_size << (PMD_SHIFT - PAGE_SHIFT - 1);
}

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