[PATCH 5.14 026/151] arm64/hugetlb: fix CMA gigantic page order for non-4K PAGE_SIZE

[Greg Kroah-Hartman]

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