[PATCH/RFC] Rework ptep_set_access_flags and fix sun4c

Benjamin Herrenschmidt
2007-05-22T06:28:59Z

This patch reworks ptep_set_access_flags() and the callers so that the
comparison to the old PTE is done inside that function, which then
returns wether an update_mmu_cache() is needed. That allows fixing
the sun4c situation where update_mmu_cache() needs to be forced,
always.

Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
---

Ok, so that's only compile tested on sparc32 and powerpc 32 bits, boot
tested on powerpc64 and not tested on others (I could use some help
testing x86, x86_64 and s390 who also have their own implementations).

Index: linux-work/include/asm-generic/pgtable.h
===================================================================
--- linux-work.orig/include/asm-generic/pgtable.h 2007-05-22 15:04:45.000000000 +1000
+++ linux-work/include/asm-generic/pgtable.h 2007-05-22 15:32:21.000000000 +1000
@@ -27,13 +27,20 @@ do { \
* Largely same as above, but only sets the access flags (dirty,
* accessed, and writable). Furthermore, we know it always gets set
* to a "more permissive" setting, which allows most architectures
- * to optimize this.
+ * to optimize this. We return wether the PTE actually changed, which
+ * in turn instructs the caller to do things like update__mmu_cache.
+ * This used to be done in the caller, but sparc needs minor faults to
+ * force that call on sun4c so we changed this macro slightly
*/
#define ptep_set_access_flags(__vma, __address, __ptep, __entry, __dirty) \
-do { \
- set_pte_at((__vma)->vm_mm, (__address), __ptep, __entry); \
- flush_tlb_page(__vma, __address); \
-} while (0)
+({ \
+ int __changed = !pte_same(*(__ptep), __entry); \
+ if (__changed) { \
+ set_pte_at((__vma)->vm_mm, (__address), __ptep, __entry); \
+ flush_tlb_page(__vma, __address); \
+ } \
+ __changed; \
+})
#endif

#ifndef __HAVE_ARCH_PTEP_TEST_AND_CLEAR_YOUNG
Index: linux-work/include/asm-powerpc/pgtable-ppc64.h
===================================================================
--- linux-work.orig/include/asm-powerpc/pgtable-ppc64.h 2007-05-22 15:04:45.000000000 +1000
+++ linux-work/include/asm-powerpc/pgtable-ppc64.h 2007-05-22 15:27:21.000000000 +1000
@@ -413,10 +413,14 @@ static inline void __ptep_set_access_fla
:"cc");
}
#define ptep_set_access_flags(__vma, __address, __ptep, __entry, __dirty) \
- do { \
- __ptep_set_access_flags(__ptep, __entry, __dirty); \
- flush_tlb_page_nohash(__vma, __address); \
- } while(0)
+({ \
+ int __changed = !pte_same(*(__ptep), __entry); \
+ if (__changed) { \
+ __ptep_set_access_flags(__ptep, __entry, __dirty); \
+ flush_tlb_page_nohash(__vma, __address); \
+ } \
+ __changed; \
+})

/*
* Macro to mark a page protection value as "uncacheable".
Index: linux-work/mm/memory.c
===================================================================
--- linux-work.orig/mm/memory.c 2007-05-22 15:04:45.000000000 +1000
+++ linux-work/mm/memory.c 2007-05-22 15:38:19.000000000 +1000
@@ -1691,9 +1691,10 @@ static int do_wp_page(struct mm_struct *
flush_cache_page(vma, address, pte_pfn(orig_pte));
entry = pte_mkyoung(orig_pte);
entry = maybe_mkwrite(pte_mkdirty(entry), vma);
- ptep_set_access_flags(vma, address, page_table, entry, 1);
- update_mmu_cache(vma, address, entry);
- lazy_mmu_prot_update(entry);
+ if (ptep_set_access_flags(vma, address, page_table, entry,1)) {
+ update_mmu_cache(vma, address, entry);
+ lazy_mmu_prot_update(entry);
+ }
ret |= VM_FAULT_WRITE;
goto unlock;
}
@@ -2525,10 +2526,9 @@ static inline int handle_pte_fault(struc
pte_t *pte, pmd_t *pmd, int write_access)
{
pte_t entry;
- pte_t old_entry;
spinlock_t *ptl;

- old_entry = entry = *pte;
+ entry = *pte;
if (!pte_present(entry)) {
if (pte_none(entry)) {
if (vma->vm_ops) {
@@ -2561,8 +2561,7 @@ static inline int handle_pte_fault(struc
entry = pte_mkdirty(entry);
}
entry = pte_mkyoung(entry);
- if (!pte_same(old_entry, entry)) {
- ptep_set_access_flags(vma, address, pte, entry, write_access);
+ if (ptep_set_access_flags(vma, address, pte, entry, write_access)) {
update_mmu_cache(vma, address, entry);
lazy_mmu_prot_update(entry);
} else {
Index: linux-work/include/asm-powerpc/pgtable-ppc32.h
===================================================================
--- linux-work.orig/include/asm-powerpc/pgtable-ppc32.h 2007-05-22 15:04:45.000000000 +1000
+++ linux-work/include/asm-powerpc/pgtable-ppc32.h 2007-05-22 15:26:07.000000000 +1000
@@ -673,10 +673,14 @@ static inline void __ptep_set_access_fla
}

#define ptep_set_access_flags(__vma, __address, __ptep, __entry, __dirty) \
- do { \
- __ptep_set_access_flags(__ptep, __entry, __dirty); \
- flush_tlb_page_nohash(__vma, __address); \
- } while(0)
+({ \
+ int __changed = !pte_same(*(__ptep), __entry); \
+ if (__changed) { \
+ __ptep_set_access_flags(__ptep, __entry, __dirty); \
+ flush_tlb_page_nohash(__vma, __address); \
+ } \
+ __changed; \
+})

/*
* Macro to mark a page protection value as "uncacheable".
Index: linux-work/include/asm-i386/pgtable.h
===================================================================
--- linux-work.orig/include/asm-i386/pgtable.h 2007-05-22 15:06:17.000000000 +1000
+++ linux-work/include/asm-i386/pgtable.h 2007-05-22 15:16:11.000000000 +1000
@@ -285,13 +285,15 @@ static inline pte_t native_local_ptep_ge
*/
#define __HAVE_ARCH_PTEP_SET_ACCESS_FLAGS
#define ptep_set_access_flags(vma, address, ptep, entry, dirty) \
-do { \
- if (dirty) { \
+({ \
+ int __changed = !pte_same(*(__ptep), __entry); \
+ if (__changed && dirty) { \
(ptep)->pte_low = (entry).pte_low; \
pte_update_defer((vma)->vm_mm, (address), (ptep)); \
flush_tlb_page(vma, address); \
} \
-} while (0)
+ __changed; \
+})

#define __HAVE_ARCH_PTEP_TEST_AND_CLEAR_DIRTY
#define ptep_test_and_clear_dirty(vma, addr, ptep) ({ \
Index: linux-work/include/asm-ppc/pgtable.h
===================================================================
--- linux-work.orig/include/asm-ppc/pgtable.h 2007-05-22 15:25:58.000000000 +1000
+++ linux-work/include/asm-ppc/pgtable.h 2007-05-22 15:26:08.000000000 +1000
@@ -694,10 +694,14 @@ static inline void __ptep_set_access_fla
}

#define ptep_set_access_flags(__vma, __address, __ptep, __entry, __dirty) \
- do { \
- __ptep_set_access_flags(__ptep, __entry, __dirty); \
- flush_tlb_page_nohash(__vma, __address); \
- } while(0)
+({ \
+ int __changed = !pte_same(*(__ptep), __entry); \
+ if (__changed) { \
+ __ptep_set_access_flags(__ptep, __entry, __dirty); \
+ flush_tlb_page_nohash(__vma, __address); \
+ } \
+ __changed; \
+})

/*
* Macro to mark a page protection value as "uncacheable".
Index: linux-work/include/asm-s390/pgtable.h
===================================================================
--- linux-work.orig/include/asm-s390/pgtable.h 2007-05-22 15:16:48.000000000 +1000
+++ linux-work/include/asm-s390/pgtable.h 2007-05-22 15:20:16.000000000 +1000
@@ -744,7 +744,12 @@ ptep_establish(struct vm_area_struct *vm
}

#define ptep_set_access_flags(__vma, __address, __ptep, __entry, __dirty) \
- ptep_establish(__vma, __address, __ptep, __entry)
+({ \
+ int __changed = !pte_same(*(__ptep), __entry); \
+ if (__changed) \
+ ptep_establish(__vma, __address, __ptep, __entry); \
+ __changed; \
+})

/*
* Test and clear dirty bit in storage key.
Index: linux-work/include/asm-sparc/pgtable.h
===================================================================
--- linux-work.orig/include/asm-sparc/pgtable.h 2007-05-22 15:30:48.000000000 +1000
+++ linux-work/include/asm-sparc/pgtable.h 2007-05-22 15:35:56.000000000 +1000
@@ -446,6 +446,17 @@ extern int io_remap_pfn_range(struct vm_
#define GET_IOSPACE(pfn) (pfn >> (BITS_PER_LONG - 4))
#define GET_PFN(pfn) (pfn & 0x0fffffffUL)

+#define __HAVE_ARCH_PTEP_SET_ACCESS_FLAGS
+#define ptep_set_access_flags(__vma, __address, __ptep, __entry, __dirty) \
+({ \
+ int __changed = !pte_same(*(__ptep), __entry); \
+ if (__changed) { \
+ set_pte_at((__vma)->vm_mm, (__address), __ptep, __entry); \
+ flush_tlb_page(__vma, __address); \
+ } \
+ (sparc_cpu_model == sun4c) || __changed; \
+})
+
#include <asm-generic/pgtable.h>

#endif /* !(__ASSEMBLY__) */
Index: linux-work/include/asm-x86_64/pgtable.h
===================================================================
--- linux-work.orig/include/asm-x86_64/pgtable.h 2007-05-22 15:20:40.000000000 +1000
+++ linux-work/include/asm-x86_64/pgtable.h 2007-05-22 15:21:52.000000000 +1000
@@ -395,12 +395,14 @@ static inline pte_t pte_modify(pte_t pte
* bit at the same time. */
#define __HAVE_ARCH_PTEP_SET_ACCESS_FLAGS
#define ptep_set_access_flags(__vma, __address, __ptep, __entry, __dirty) \
- do { \
- if (__dirty) { \
- set_pte(__ptep, __entry); \
- flush_tlb_page(__vma, __address); \
- } \
- } while (0)
+({ \
+ int __changed = !pte_same(*(__ptep), __entry); \
+ if (__changed && __dirty) { \
+ set_pte(__ptep, __entry); \
+ flush_tlb_page(__vma, __address); \
+ } \
+ __changed; \
+})

/* Encode and de-code a swap entry */
#define __swp_type(x) (((x).val >> 1) & 0x3f)