[S390] refactor page table functions for better pgste support

Rework the architecture page table functions to access the bits in the
page table extension array (pgste). There are a number of changes:
1) Fix missing pgste update if the attach_count for the mm is <= 1.
2) For every operation that affects the invalid bit in the pte or the
   rcp byte in the pgste the pcl lock needs to be acquired. The function
   pgste_get_lock gets the pcl lock and returns the current pgste value
   for a pte pointer. The function pgste_set_unlock stores the pgste
   and releases the lock. Between these two calls the bits in the pgste
   can be shuffled.
3) Define two software bits in the pte _PAGE_SWR and _PAGE_SWC to avoid
   calling SetPageDirty and SetPageReferenced from pgtable.h. If the
   host reference backup bit or the host change backup bit has been
   set the dirty/referenced state is transfered to the pte. The common
   code will pick up the state from the pte.
4) Add ptep_modify_prot_start and ptep_modify_prot_commit for mprotect.
5) Remove pgd_populate_kernel, pud_populate_kernel, pmd_populate_kernel
   pgd_clear_kernel, pud_clear_kernel, pmd_clear_kernel and ptep_invalidate.
6) Rename kvm_s390_test_and_clear_page_dirty to
   ptep_test_and_clear_user_dirty and add ptep_test_and_clear_user_young.
7) Define mm_exclusive() and mm_has_pgste() helper to improve readability.

Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>

arch/s390/mm/init.c

@@ -175,7 +175,8 @@ void kernel_map_pages(struct page *page, int numpages, int enable)
 		pmd = pmd_offset(pud, address);
 		pte = pte_offset_kernel(pmd, address);
 		if (!enable) {
-			ptep_invalidate(&init_mm, address, pte);
+			__ptep_ipte(address, pte);
+			pte_val(*pte) = _PAGE_TYPE_EMPTY;
 			continue;
 		}
 		*pte = mk_pte_phys(address, __pgprot(_PAGE_TYPE_RW));

arch/s390/mm/pageattr.c

@@ -28,7 +28,7 @@ static void change_page_attr(unsigned long addr, int numpages,
 
 		pte = *ptep;
 		pte = set(pte);
-		ptep_invalidate(&init_mm, addr, ptep);
+		__ptep_ipte(addr, ptep);
 		*ptep = pte;
 		addr += PAGE_SIZE;
 	}

arch/s390/mm/vmem.c

@@ -95,7 +95,7 @@ static int vmem_add_mem(unsigned long start, unsigned long size, int ro)
 			pu_dir = vmem_pud_alloc();
 			if (!pu_dir)
 				goto out;
-			pgd_populate_kernel(&init_mm, pg_dir, pu_dir);
+			pgd_populate(&init_mm, pg_dir, pu_dir);
 		}
 
 		pu_dir = pud_offset(pg_dir, address);
@@ -103,7 +103,7 @@ static int vmem_add_mem(unsigned long start, unsigned long size, int ro)
 			pm_dir = vmem_pmd_alloc();
 			if (!pm_dir)
 				goto out;
-			pud_populate_kernel(&init_mm, pu_dir, pm_dir);
+			pud_populate(&init_mm, pu_dir, pm_dir);
 		}
 
 		pte = mk_pte_phys(address, __pgprot(ro ? _PAGE_RO : 0));
@@ -123,7 +123,7 @@ static int vmem_add_mem(unsigned long start, unsigned long size, int ro)
 			pt_dir = vmem_pte_alloc();
 			if (!pt_dir)
 				goto out;
-			pmd_populate_kernel(&init_mm, pm_dir, pt_dir);
+			pmd_populate(&init_mm, pm_dir, pt_dir);
 		}
 
 		pt_dir = pte_offset_kernel(pm_dir, address);
@@ -159,7 +159,7 @@ static void vmem_remove_range(unsigned long start, unsigned long size)
 			continue;
 
 		if (pmd_huge(*pm_dir)) {
-			pmd_clear_kernel(pm_dir);
+			pmd_clear(pm_dir);
 			address += HPAGE_SIZE - PAGE_SIZE;
 			continue;
 		}
@@ -192,7 +192,7 @@ int __meminit vmemmap_populate(struct page *start, unsigned long nr, int node)
 			pu_dir = vmem_pud_alloc();
 			if (!pu_dir)
 				goto out;
-			pgd_populate_kernel(&init_mm, pg_dir, pu_dir);
+			pgd_populate(&init_mm, pg_dir, pu_dir);
 		}
 
 		pu_dir = pud_offset(pg_dir, address);
@@ -200,7 +200,7 @@ int __meminit vmemmap_populate(struct page *start, unsigned long nr, int node)
 			pm_dir = vmem_pmd_alloc();
 			if (!pm_dir)
 				goto out;
-			pud_populate_kernel(&init_mm, pu_dir, pm_dir);
+			pud_populate(&init_mm, pu_dir, pm_dir);
 		}
 
 		pm_dir = pmd_offset(pu_dir, address);
@@ -208,7 +208,7 @@ int __meminit vmemmap_populate(struct page *start, unsigned long nr, int node)
 			pt_dir = vmem_pte_alloc();
 			if (!pt_dir)
 				goto out;
-			pmd_populate_kernel(&init_mm, pm_dir, pt_dir);
+			pmd_populate(&init_mm, pm_dir, pt_dir);
 		}
 
 		pt_dir = pte_offset_kernel(pm_dir, address);