[PATCH] arm64/mm: Validate CONFIG_PGTABLE_LEVELS

[Anshuman Khandual]

CONFIG_PGTABLE_LEVELS has been statically defined in (arch/arm64/Kconfig)
depending on the page size and requested virtual address range. In order to
validate this page table levels selection this adds a BUILD_BUG_ON() as per
the existing formula ARM64_HW_PGTABLE_LEVELS(). This would help protect any
inadvertent changes to CONFIG_PGTABLE_LEVELS selection.

Cc: Catalin Marinas <catalin.marinas at arm.com>
Cc: Will Deacon <will at kernel.org>
Cc: Mark Rutland <mark.rutland at arm.com>
Cc: linux-arm-kernel at lists.infradead.org
Cc: linux-kernel at vger.kernel.org
Signed-off-by: Anshuman Khandual <anshuman.khandual at arm.com>
---
This applies on v5.13-rc1.

 arch/arm64/mm/init.c | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/arch/arm64/mm/init.c b/arch/arm64/mm/init.c
index 16a2b2b1c54d..b4da42f3d584 100644
--- a/arch/arm64/mm/init.c
+++ b/arch/arm64/mm/init.c
@@ -498,6 +498,13 @@ void __init mem_init(void)
 	BUILD_BUG_ON(TASK_SIZE_32 > DEFAULT_MAP_WINDOW_64);
 #endif
 
+	/*
+	 * Selected page table levels should match when derived from
+	 * scratch using the virtual address range and page size.
+	 */
+	BUILD_BUG_ON(ARM64_HW_PGTABLE_LEVELS(CONFIG_ARM64_VA_BITS) !=
+		     CONFIG_PGTABLE_LEVELS);
+
 	if (PAGE_SIZE >= 16384 && get_num_physpages() <= 128) {
 		extern int sysctl_overcommit_memory;
 		/*
-- 
2.20.1