[BUGFIX][PATCH] flush icache before set_pte() in ia64 take7, [2/2]sync icache dcache

From: KAMEZAWA Hiroyuki
Date: Tue Aug 07 2007 - 04:26:53 EST

flush icache for ia64 take7.

Changes V6 -> V7:
- adjusted against 2.6.23-rc2

Changes V5 -> V6:
- no changes. (added new patches to the patch set)

Changes V4 -> V5:
- removed sync_icache_dcache from do_wp_page() page reuse case.

Changes v3 -> v4:
- avoid implementing flush_(i)cache_pages().
- added sync_icache_dcache() call.
- change Documentation/cachetlb.txt

Current ia64 kernel flushes icache by lazy_mmu_prot_update() *after*
set_pte(). This is wrong. This patch removes lazy_mmu_prot_update and
add sync_icache_dcache(). sync_icache_dcache() is called before set_pte()
if necessary and synchronize icache with dcache (fc.i instruction).

This patch fixes SIGILL problem on NFS/ia64.

About Icache-Dcache inconsistency in ia64
- When the cache line is modified, Icache and Dcache are purged.

- When I-cache misses, I-cache will access just the lower layer cache(memory).
Then, If the lower_layer_cache is not up-to-date, I-cache will see
old information. For avoiding this case, Icache-Dcache synchronization(fc.i)
is necessary. (Icache-Dcache synchronization means making Dcache and lower
layer unified cache(memory) consistent.)

Details:
- In general, cache flushing macro are used for virtually tagged caches.
IA64 has physically tagged caches but doesn't guarantee consistency
between Icache and Dcache. So, new macro, sync_icache_dcache() is added.
This is NO-OP in other archs.
- sync_icache_dcache() only works if pte is executable.
- sync_icache_dcache must be called before set_pte().
- A page which is consistent is marked as PG_arch_1.

About changes in generic codes:
- do_wp_page() ....need to sync newly copied page.
Here, lazy_mmu_prot_update() was done before set_pte().
This was because SIGILL in JAVA was reported and quick
fix was applied.

- do_anonymous_page() .... newly installed anon pages doesn't contains any
instruction when set_pte() is executed, icache-dcache
synchronization is not necessary.

- __do_fault() .... need to sync newly-installed page.

- handle_pte_fault() .... just changes access bit...then, no need to sync.

- remove_migration_pte().... need to sync newly-installed page.


- change_pte_range() .... need to sync icache-dcache. When a user writes
instruction into the page and modifies protection to be
executable, it should be synced.

- hugetlb_change_protection() .... Maybe cache will be expired...but
it is safe to sync Icache before set_pte().

- page_mkclean_one() .... no need to sync icache-dcache. There is no page
contents modification. And there is no protection
change.

Thanks to Zoltan Menyhart for his advices.

Signed-off-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@xxxxxxxxxxxxxx>

---
Documentation/cachetlb.txt | 11 +++++++----
arch/ia64/mm/init.c | 6 ++----
include/asm-generic/pgtable.h | 8 ++++----
include/asm-ia64/pgtable.h | 15 ++++++++++-----
mm/hugetlb.c | 3 +--
mm/memory.c | 7 ++-----
mm/migrate.c | 2 +-
mm/mprotect.c | 2 +-
mm/rmap.c | 1 -
9 files changed, 28 insertions(+), 27 deletions(-)

Index: linux-2.6.23-rc2.test/include/asm-generic/pgtable.h
===================================================================
--- linux-2.6.23-rc2.test.orig/include/asm-generic/pgtable.h
+++ linux-2.6.23-rc2.test/include/asm-generic/pgtable.h
@@ -124,14 +124,14 @@ static inline void ptep_set_wrprotect(st
#define pgd_offset_gate(mm, addr) pgd_offset(mm, addr)
#endif

-#ifndef __HAVE_ARCH_LAZY_MMU_PROT_UPDATE
-#define lazy_mmu_prot_update(pte) do { } while (0)
-#endif
-
#ifndef __HAVE_ARCH_MOVE_PTE
#define move_pte(pte, prot, old_addr, new_addr) (pte)
#endif

+#ifndef __HAVE_ARCH_SYNC_ICACHE_DCACHE
+#define sync_icache_dcache(pte) do {} while (0)
+#endif
+
/*
* A facility to provide lazy MMU batching. This allows PTE updates and
* page invalidations to be delayed until a call to leave lazy MMU mode
Index: linux-2.6.23-rc2.test/include/asm-ia64/pgtable.h
===================================================================
--- linux-2.6.23-rc2.test.orig/include/asm-ia64/pgtable.h
+++ linux-2.6.23-rc2.test/include/asm-ia64/pgtable.h
@@ -484,11 +484,18 @@ extern struct page *zero_page_memmap_ptr
#endif

/*
- * IA-64 doesn't have any external MMU info: the page tables contain all the necessary
- * information. However, we use this routine to take care of any (delayed) i-cache
- * flushing that may be necessary.
+ * IA-64 doesn't guarantee Icache is consistent with Dcache. For ensure
+ * Icache consistency, we have to synchronize them before setting pte
+ * as an executable pte.
*/
-extern void lazy_mmu_prot_update (pte_t pte);
+extern void __sync_icache_dcache(pte_t pte);
+static inline void sync_icache_dcache(pte_t pte)
+{
+ if (pte_exec(pte))
+ __sync_icache_dcache(pte);
+}
+#define __HAVE_ARCH_SYNC_ICACHE_DCACHE
+

#define __HAVE_ARCH_PTEP_SET_ACCESS_FLAGS
/*
@@ -578,7 +585,6 @@ extern void lazy_mmu_prot_update (pte_t
#define __HAVE_ARCH_PTEP_SET_WRPROTECT
#define __HAVE_ARCH_PTE_SAME
#define __HAVE_ARCH_PGD_OFFSET_GATE
-#define __HAVE_ARCH_LAZY_MMU_PROT_UPDATE

#ifndef CONFIG_PGTABLE_4
#include <asm-generic/pgtable-nopud.h>
Index: linux-2.6.23-rc2.test/Documentation/cachetlb.txt
===================================================================
--- linux-2.6.23-rc2.test.orig/Documentation/cachetlb.txt
+++ linux-2.6.23-rc2.test/Documentation/cachetlb.txt
@@ -133,11 +133,14 @@ changes occur:
The ia64 sn2 platform is one example of a platform
that uses this interface.

-8) void lazy_mmu_prot_update(pte_t pte)
- This interface is called whenever the protection on
- any user PTEs change. This interface provides a notification
- to architecture specific code to take appropriate action.
+8) void sync_icache_dcache(pte_t pte)
+ This interface is used for synchronize icache and dcache.
+ Even if the cache is physically tagged, some archs doesn't
+ guarantee consistency between I-cache and D-cache. In such arch,
+ we need to synchronize I-cache and D-cache before installing
+ executable pages.

+ This is used only for ia64 now.

Next, we have the cache flushing interfaces. In general, when Linux
is changing an existing virtual-->physical mapping to a new value,
Index: linux-2.6.23-rc2.test/mm/memory.c
===================================================================
--- linux-2.6.23-rc2.test.orig/mm/memory.c
+++ linux-2.6.23-rc2.test/mm/memory.c
@@ -1699,7 +1699,6 @@ static int do_wp_page(struct mm_struct *
entry = maybe_mkwrite(pte_mkdirty(entry), vma);
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;
@@ -1741,7 +1740,7 @@ gotten:
flush_cache_page(vma, address, pte_pfn(orig_pte));
entry = mk_pte(new_page, vma->vm_page_prot);
entry = maybe_mkwrite(pte_mkdirty(entry), vma);
- lazy_mmu_prot_update(entry);
+ sync_icache_dcache(entry);
/*
* Clear the pte entry and flush it first, before updating the
* pte with the new entry. This will avoid a race condition
@@ -2286,7 +2285,6 @@ static int do_anonymous_page(struct mm_s

/* No need to invalidate - it was non-present before */
update_mmu_cache(vma, address, entry);
- lazy_mmu_prot_update(entry);
unlock:
pte_unmap_unlock(page_table, ptl);
return 0;
@@ -2419,6 +2417,7 @@ static int __do_fault(struct mm_struct *
if (likely(pte_same(*page_table, orig_pte))) {
flush_icache_page(vma, page);
entry = mk_pte(page, vma->vm_page_prot);
+ sync_icache_dcache(entry);
if (flags & FAULT_FLAG_WRITE)
entry = maybe_mkwrite(pte_mkdirty(entry), vma);
set_pte_at(mm, address, page_table, entry);
@@ -2437,7 +2436,6 @@ static int __do_fault(struct mm_struct *

/* no need to invalidate: a not-present page won't be cached */
update_mmu_cache(vma, address, entry);
- lazy_mmu_prot_update(entry);
} else {
if (anon)
page_cache_release(page);
@@ -2611,7 +2609,6 @@ static inline int handle_pte_fault(struc
entry = pte_mkyoung(entry);
if (ptep_set_access_flags(vma, address, pte, entry, write_access)) {
update_mmu_cache(vma, address, entry);
- lazy_mmu_prot_update(entry);
} else {
/*
* This is needed only for protection faults but the arch code
Index: linux-2.6.23-rc2.test/mm/migrate.c
===================================================================
--- linux-2.6.23-rc2.test.orig/mm/migrate.c
+++ linux-2.6.23-rc2.test/mm/migrate.c
@@ -172,6 +172,7 @@ static void remove_migration_pte(struct
if (is_write_migration_entry(entry))
pte = pte_mkwrite(pte);
flush_cache_page(vma, addr, pte_pfn(pte));
+ sync_icache_dcache(pte);
set_pte_at(mm, addr, ptep, pte);

if (PageAnon(new))
@@ -181,7 +182,6 @@ static void remove_migration_pte(struct

/* No need to invalidate - it was non-present before */
update_mmu_cache(vma, addr, pte);
- lazy_mmu_prot_update(pte);

out:
pte_unmap_unlock(ptep, ptl);
Index: linux-2.6.23-rc2.test/mm/hugetlb.c
===================================================================
--- linux-2.6.23-rc2.test.orig/mm/hugetlb.c
+++ linux-2.6.23-rc2.test/mm/hugetlb.c
@@ -353,7 +353,6 @@ static void set_huge_ptep_writable(struc
entry = pte_mkwrite(pte_mkdirty(*ptep));
if (ptep_set_access_flags(vma, address, ptep, entry, 1)) {
update_mmu_cache(vma, address, entry);
- lazy_mmu_prot_update(entry);
}
}

@@ -705,8 +704,8 @@ void hugetlb_change_protection(struct vm
if (!pte_none(*ptep)) {
pte = huge_ptep_get_and_clear(mm, address, ptep);
pte = pte_mkhuge(pte_modify(pte, newprot));
+ sync_icache_dcache(pte);
set_huge_pte_at(mm, address, ptep, pte);
- lazy_mmu_prot_update(pte);
}
}
spin_unlock(&mm->page_table_lock);
Index: linux-2.6.23-rc2.test/arch/ia64/mm/init.c
===================================================================
--- linux-2.6.23-rc2.test.orig/arch/ia64/mm/init.c
+++ linux-2.6.23-rc2.test/arch/ia64/mm/init.c
@@ -53,16 +53,13 @@ EXPORT_SYMBOL(vmem_map);
struct page *zero_page_memmap_ptr; /* map entry for zero page */
EXPORT_SYMBOL(zero_page_memmap_ptr);

-void
-lazy_mmu_prot_update (pte_t pte)
+void __sync_icache_dcache(pte_t pte)
{
unsigned long addr;
struct page *page;
unsigned long order;

- if (!pte_exec(pte))
- return; /* not an executable page... */
-
+ BUG_ON(!pte_exec(pte));
page = pte_page(pte);
addr = (unsigned long) page_address(page);

Index: linux-2.6.23-rc2.test/mm/mprotect.c
===================================================================
--- linux-2.6.23-rc2.test.orig/mm/mprotect.c
+++ linux-2.6.23-rc2.test/mm/mprotect.c
@@ -52,8 +52,8 @@ static void change_pte_range(struct mm_s
*/
if (dirty_accountable && pte_dirty(ptent))
ptent = pte_mkwrite(ptent);
+ sync_icache_dcache(ptent);
set_pte_at(mm, addr, pte, ptent);
- lazy_mmu_prot_update(ptent);
#ifdef CONFIG_MIGRATION
} else if (!pte_file(oldpte)) {
swp_entry_t entry = pte_to_swp_entry(oldpte);
Index: linux-2.6.23-rc2.test/mm/rmap.c
===================================================================
--- linux-2.6.23-rc2.test.orig/mm/rmap.c
+++ linux-2.6.23-rc2.test/mm/rmap.c
@@ -436,7 +436,6 @@ static int page_mkclean_one(struct page
entry = pte_wrprotect(entry);
entry = pte_mkclean(entry);
set_pte_at(mm, address, pte, entry);
- lazy_mmu_prot_update(entry);
ret = 1;
}


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