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