[1/6] Xen VMM #4: add ptep_establish_new to make va available

[Ian Pratt <Ian.Pratt@cl.cam.ac.uk>]

This patch adds 'ptep_establish_new', in keeping with the
existing 'ptep_establish', but for use where a mapping is being
established where there was previously none present. This
function is useful (rather than just using set_pte) because
having the virtual address available enables a very important
optimisation for arch-xen. We introduce
HAVE_ARCH_PTEP_ESTABLISH_NEW and define a generic implementation
in asm-generic/pgtable.h, following the pattern of the existing
ptep_establish.

Signed-off-by: ian.pratt@cl.cam.ac.uk

---

diff -Nurp pristine-linux-2.6.10-rc3/include/asm-generic/pgtable.h tmp-linux-2.6.10-rc3-xen.patch/include/asm-generic/pgtable.h
--- pristine-linux-2.6.10-rc3/include/asm-generic/pgtable.h	2004-12-03 21:53:20.000000000 +0000
+++ tmp-linux-2.6.10-rc3-xen.patch/include/asm-generic/pgtable.h	2004-12-08 00:52:40.000000000 +0000
@@ -42,6 +42,16 @@ do {				  					  \
 } while (0)
 #endif
 
+#ifndef __HAVE_ARCH_PTEP_ESTABLISH_NEW
+/*
+ * Establish a mapping where none previously existed
+ */
+#define ptep_establish_new(__vma, __address, __ptep, __entry)		\
+do {									\
+	set_pte(__ptep, __entry);					\
+} while (0)
+#endif
+
 #ifndef __HAVE_ARCH_PTEP_TEST_AND_CLEAR_YOUNG
 static inline int ptep_test_and_clear_young(pte_t *ptep)
 {
diff -Nurp pristine-linux-2.6.10-rc3/mm/memory.c tmp-linux-2.6.10-rc3-xen.patch/mm/memory.c
--- pristine-linux-2.6.10-rc3/mm/memory.c	2004-12-03 21:53:46.000000000 +0000
+++ tmp-linux-2.6.10-rc3-xen.patch/mm/memory.c	2004-12-08 00:56:47.000000000 +0000
@@ -1468,7 +1468,7 @@ do_anonymous_page(struct mm_struct *mm, 
 		page_add_anon_rmap(page, vma, addr);
 	}
 
-	set_pte(page_table, entry);
+	ptep_establish_new(vma, addr, page_table, entry);
 	pte_unmap(page_table);
 
 	/* No need to invalidate - it was non-present before */
@@ -1573,7 +1573,7 @@ retry:
 		entry = mk_pte(new_page, vma->vm_page_prot);
 		if (write_access)
 			entry = maybe_mkwrite(pte_mkdirty(entry), vma);
-		set_pte(page_table, entry);
+		ptep_establish_new(vma, address, page_table, entry);
 		if (anon) {
 			lru_cache_add_active(new_page);
 			page_add_anon_rmap(new_page, vma, address);