arm64: mm: allow sections for unaligned bases

Callees of __create_mapping may decide to create section mappings if
sufficient low bits of the physical and virtual addresses they were
passed are zero. While __create_mapping rounds the virtual base address
down, it does not similarly round the physical base address down, and
hence non-zero bits in the physical address can prevent use of a section
mapping, even where a whole next-level table would be used instead.

Round down the physical base address in __create_mapping to enable all
callees to always create section mappings when such a mapping is
possible.

Cc: Laura Abbott <[email protected]>
Acked-by: Ard Biesheuvel <[email protected]>
Acked-by: Catalin Marinas <[email protected]>
Reviewed-by: Steve Capper <[email protected]>
Signed-off-by: Mark Rutland <[email protected]>
Signed-off-by: Will Deacon <[email protected]>

Author: mrutland-arm

arch/arm64/mm/mmu.c

@@ -258,6 +258,7 @@ static void  __create_mapping(struct mm_struct *mm, pgd_t *pgd,
 	if (WARN_ON((phys ^ virt) & ~PAGE_MASK))
 		return;
 
+	phys &= PAGE_MASK;
 	addr = virt & PAGE_MASK;
 	length = PAGE_ALIGN(size + (virt & ~PAGE_MASK));