s390/mm: fix pmd_huge() usage for kernel mapping

pmd_huge() will always return 0 on !HUGETLBFS, however we use that helper
function when walking the kernel page tables to decide if we have a
1MB page frame or not.
Since we create 1MB frames for the kernel 1:1 mapping independently of
HUGETLBFS this can lead to incorrect storage accesses since the code
can assume that we have a pointer to a page table instead of a pointer
to a 1MB frame.

Fix this by adding a pmd_large() primitive like other architectures have
it already and remove all references to HUGETLBFS/HUGETLBPAGE from the
code that walks kernel page tables.
Reviewed-by: Gerald Schaefer <gerald.schaefer@de.ibm.com>
Signed-off-by: Heiko Carstens <heiko.carstens@de.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>

arch/s390/include/asm/pgtable.h

@@ -507,6 +507,15 @@ static inline int pmd_none(pmd_t pmd)
 	return (pmd_val(pmd) & _SEGMENT_ENTRY_INV) != 0UL;
 }
 
+static inline int pmd_large(pmd_t pmd)
+{
+#ifdef CONFIG_64BIT
+	return !!(pmd_val(pmd) & _SEGMENT_ENTRY_LARGE);
+#else
+	return 0;
+#endif
+}
+
 static inline int pmd_bad(pmd_t pmd)
 {
 	unsigned long mask = ~_SEGMENT_ENTRY_ORIGIN & ~_SEGMENT_ENTRY_INV;

arch/s390/mm/pageattr.c

@@ -21,7 +21,7 @@ static void change_page_attr(unsigned long addr, int numpages,
 		pgdp = pgd_offset(&init_mm, addr);
 		pudp = pud_offset(pgdp, addr);
 		pmdp = pmd_offset(pudp, addr);
-		if (pmd_huge(*pmdp)) {
+		if (pmd_large(*pmdp)) {
 			WARN_ON_ONCE(1);
 			continue;
 		}

arch/s390/mm/vmem.c

@@ -79,7 +79,8 @@ static pte_t __ref *vmem_pte_alloc(unsigned long address)
  */
 static int vmem_add_mem(unsigned long start, unsigned long size, int ro)
 {
-	unsigned long address;
+	unsigned long end = start + size;
+	unsigned long address = start;
 	pgd_t *pg_dir;
 	pud_t *pu_dir;
 	pmd_t *pm_dir;
@@ -87,7 +88,7 @@ static int vmem_add_mem(unsigned long start, unsigned long size, int ro)
 	pte_t  pte;
 	int ret = -ENOMEM;
 
-	for (address = start; address < start + size; address += PAGE_SIZE) {
+	while (address < end) {
 		pg_dir = pgd_offset_k(address);
 		if (pgd_none(*pg_dir)) {
 			pu_dir = vmem_pud_alloc();
@@ -108,12 +109,11 @@ static int vmem_add_mem(unsigned long start, unsigned long size, int ro)
 		pm_dir = pmd_offset(pu_dir, address);
 
 #if defined(CONFIG_64BIT) && !defined(CONFIG_DEBUG_PAGEALLOC)
-		if (MACHINE_HAS_HPAGE && !(address & ~HPAGE_MASK) &&
-		    (address + HPAGE_SIZE <= start + size) &&
-		    (address >= HPAGE_SIZE)) {
+		if (MACHINE_HAS_EDAT1 && address && !(address & ~PMD_MASK) &&
+		    (address + PMD_SIZE <= end)) {
 			pte_val(pte) |= _SEGMENT_ENTRY_LARGE;
 			pmd_val(*pm_dir) = pte_val(pte);
-			address += HPAGE_SIZE - PAGE_SIZE;
+			address += PMD_SIZE;
 			continue;
 		}
 #endif
@@ -126,10 +126,11 @@ static int vmem_add_mem(unsigned long start, unsigned long size, int ro)
 
 		pt_dir = pte_offset_kernel(pm_dir, address);
 		*pt_dir = pte;
+		address += PAGE_SIZE;
 	}
 	ret = 0;
 out:
-	flush_tlb_kernel_range(start, start + size);
+	flush_tlb_kernel_range(start, end);
 	return ret;
 }
 
@@ -139,7 +140,8 @@ static int vmem_add_mem(unsigned long start, unsigned long size, int ro)
  */
 static void vmem_remove_range(unsigned long start, unsigned long size)
 {
-	unsigned long address;
+	unsigned long end = start + size;
+	unsigned long address = start;
 	pgd_t *pg_dir;
 	pud_t *pu_dir;
 	pmd_t *pm_dir;
@@ -147,7 +149,7 @@ static void vmem_remove_range(unsigned long start, unsigned long size)
 	pte_t  pte;
 
 	pte_val(pte) = _PAGE_TYPE_EMPTY;
-	for (address = start; address < start + size; address += PAGE_SIZE) {
+	while (address < end) {
 		pg_dir = pgd_offset_k(address);
 		pu_dir = pud_offset(pg_dir, address);
 		if (pud_none(*pu_dir))
@@ -155,17 +157,16 @@ static void vmem_remove_range(unsigned long start, unsigned long size)
 		pm_dir = pmd_offset(pu_dir, address);
 		if (pmd_none(*pm_dir))
 			continue;
-
-		if (pmd_huge(*pm_dir)) {
+		if (pmd_large(*pm_dir)) {
 			pmd_clear(pm_dir);
-			address += HPAGE_SIZE - PAGE_SIZE;
+			address += PMD_SIZE;
 			continue;
 		}
-
 		pt_dir = pte_offset_kernel(pm_dir, address);
 		*pt_dir = pte;
+		address += PAGE_SIZE;
 	}
-	flush_tlb_kernel_range(start, start + size);
+	flush_tlb_kernel_range(start, end);
 }
 
 /*