[PATCH] paravirt: fix missing pte update

The function ptep_get_and_clear uses an atomic instruction sequence to get and
clear an active pte.  Rather than add such an atomic operator to all virtual
machine implementations in paravirt-ops, it is easier to support the raw
atomic sequence and use either a trapping writable pagetable approach, or a
post-update notification.  For the post update notification, we require the
pte_update function to be called after the access.  Combine the 2-level and
3-level paging operators into one common function which does the post-update
notification, and rename the actual atomic sequences to raw_ptep_xxx
operators.
Signed-off-by: Zachary Amsden <zach@vmware.com>
Signed-off-by: Andi Kleen <ak@suse.de>
Cc: Andi Kleen <ak@muc.de>
Cc: Jeremy Fitzhardinge <jeremy@goop.org>
Cc: Chris Wright <chrisw@sous-sol.org>
Signed-off-by: Andrew Morton <akpm@osdl.org>

include/asm-i386/pgtable-2level.h

@@ -23,8 +23,7 @@
 #define pte_clear(mm,addr,xp)	do { set_pte_at(mm, addr, xp, __pte(0)); } while (0)
 #define pmd_clear(xp)	do { set_pmd(xp, __pmd(0)); } while (0)
 
-#define __HAVE_ARCH_PTEP_GET_AND_CLEAR
-#define ptep_get_and_clear(mm,addr,xp)	__pte(xchg(&(xp)->pte_low, 0))
+#define raw_ptep_get_and_clear(xp)	__pte(xchg(&(xp)->pte_low, 0))
 
 #define pte_page(x)		pfn_to_page(pte_pfn(x))
 #define pte_none(x)		(!(x).pte_low)

include/asm-i386/pgtable-3level.h

@@ -119,8 +119,7 @@ static inline void pud_clear (pud_t * pud) { }
 #define pmd_offset(pud, address) ((pmd_t *) pud_page(*(pud)) + \
 			pmd_index(address))
 
-#define __HAVE_ARCH_PTEP_GET_AND_CLEAR
-static inline pte_t ptep_get_and_clear(struct mm_struct *mm, unsigned long addr, pte_t *ptep)
+static inline pte_t raw_ptep_get_and_clear(pte_t *ptep)
 {
 	pte_t res;
 

include/asm-i386/pgtable.h

@@ -326,6 +326,14 @@ do {									\
 	__young;							\
 })
 
+#define __HAVE_ARCH_PTEP_GET_AND_CLEAR
+static inline pte_t ptep_get_and_clear(struct mm_struct *mm, unsigned long addr, pte_t *ptep)
+{
+	pte_t pte = raw_ptep_get_and_clear(ptep);
+	pte_update(mm, addr, ptep);
+	return pte;
+}
+
 #define __HAVE_ARCH_PTEP_GET_AND_CLEAR_FULL
 static inline pte_t ptep_get_and_clear_full(struct mm_struct *mm, unsigned long addr, pte_t *ptep, int full)
 {