arm64: Invalidate the TLB when replacing pmd entries during boot

With the 64K page size configuration, __create_page_tables in head.S
maps enough memory to get started but using 64K pages rather than 512M
sections with a single pgd/pud/pmd entry pointing to a pte table.
create_mapping() may override the pgd/pud/pmd table entry with a block
(section) one if the RAM size is more than 512MB and aligned correctly.
For the end of this block to be accessible, the old TLB entry must be
invalidated.

Cc: <stable@vger.kernel.org>
Reported-by: Mark Salter <msalter@redhat.com>
Tested-by: Mark Salter <msalter@redhat.com>
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>

arch/arm64/mm/mmu.c

@@ -203,10 +203,18 @@ static void __init alloc_init_pmd(pud_t *pud, unsigned long addr,
 	do {
 		next = pmd_addr_end(addr, end);
 		/* try section mapping first */
-		if (((addr | next | phys) & ~SECTION_MASK) == 0)
+		if (((addr | next | phys) & ~SECTION_MASK) == 0) {
+			pmd_t old_pmd =*pmd;
 			set_pmd(pmd, __pmd(phys | prot_sect_kernel));
-		else
+			/*
+			 * Check for previous table entries created during
+			 * boot (__create_page_tables) and flush them.
+			 */
+			if (!pmd_none(old_pmd))
+				flush_tlb_all();
+		} else {
 			alloc_init_pte(pmd, addr, next, __phys_to_pfn(phys));
+		}
 		phys += next - addr;
 	} while (pmd++, addr = next, addr != end);
 }