From: Mike Kravetz <mike.kravetz@xxxxxxxxxx> commit 2e5809a4ddb15969503e43b06662a9a725f613ea upstream. For non-4K PAGE_SIZE configs, the largest gigantic huge page size is CONT_PMD_SHIFT order. On arm64 with 64K PAGE_SIZE, the gigantic page is 16G. Therefore, one should be able to specify 'hugetlb_cma=16G' on the kernel command line so that one gigantic page can be allocated from CMA. However, when adding such an option the following message is produced: hugetlb_cma: cma area should be at least 8796093022208 MiB This is because the calculation for non-4K gigantic page order is incorrect in the arm64 specific routine arm64_hugetlb_cma_reserve(). Fixes: abb7962adc80 ("arm64/hugetlb: Reserve CMA areas for gigantic pages on 16K and 64K configs") Cc: <stable@xxxxxxxxxxxxxxx> # 5.9.x Signed-off-by: Mike Kravetz <mike.kravetz@xxxxxxxxxx> Reviewed-by: Anshuman Khandual <anshuman.khandual@xxxxxxx> Link: https://lore.kernel.org/r/20211005202529.213812-1-mike.kravetz@xxxxxxxxxx Signed-off-by: Catalin Marinas <catalin.marinas@xxxxxxx> Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx> --- arch/arm64/mm/hugetlbpage.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) --- a/arch/arm64/mm/hugetlbpage.c +++ b/arch/arm64/mm/hugetlbpage.c @@ -43,7 +43,7 @@ void __init arm64_hugetlb_cma_reserve(vo #ifdef CONFIG_ARM64_4K_PAGES order = PUD_SHIFT - PAGE_SHIFT; #else - order = CONT_PMD_SHIFT + PMD_SHIFT - PAGE_SHIFT; + order = CONT_PMD_SHIFT - PAGE_SHIFT; #endif /* * HugeTLB CMA reservation is required for gigantic