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SubjectRe: [PATCH v2 04/20] ARM: LPAE: Do not assume Linux PTEs are always at PTRS_PER_PTE offset
On Fri, Nov 12, 2010 at 06:00:24PM +0000, Catalin Marinas wrote:
> Placing the Linux PTEs at a 2KB offset inside a page is a workaround for
> the 2-level page table format where not enough spare bits are available.
> With LPAE this is no longer required. This patch changes such assumption
> by using a different macro, LINUX_PTE_OFFSET, which is defined to
> PTRS_PER_PTE for the 2-level page tables.

Hmm. I think we should be doing this a different way - in fact, I think
we should switch the order of the linux vs hardware page tables. This
actually simplifies the code a bit too - notice that we lose the arith.
in __pte_map, __pte_unmap, pmd_page_vaddr, which is all page table
walking stuff.

arch/arm/include/asm/pgalloc.h | 34 +++++++++++++++-------------------
arch/arm/include/asm/pgtable.h | 30 +++++++++++++++---------------
arch/arm/mm/fault.c | 2 +-
arch/arm/mm/mmu.c | 2 +-
arch/arm/mm/proc-macros.S | 10 +++++-----
arch/arm/mm/proc-v7.S | 8 +++-----
6 files changed, 40 insertions(+), 46 deletions(-)

diff --git a/arch/arm/include/asm/pgalloc.h b/arch/arm/include/asm/pgalloc.h
index b12cc98..e2a6613 100644
--- a/arch/arm/include/asm/pgalloc.h
+++ b/arch/arm/include/asm/pgalloc.h
@@ -38,6 +38,11 @@ extern void free_pgd_slow(struct mm_struct *mm, pgd_t *pgd);

#define PGALLOC_GFP (GFP_KERNEL | __GFP_NOTRACK | __GFP_REPEAT | __GFP_ZERO)

+static inline void clean_pte_table(void *ptr)
+{
+ clean_dcache_area(ptr + PTE_HWTABLE_OFF, PTE_HWTABLE_SIZE);
+}
+
/*
* Allocate one PTE table.
*
@@ -60,10 +65,8 @@ pte_alloc_one_kernel(struct mm_struct *mm, unsigned long addr)
pte_t *pte;

pte = (pte_t *)__get_free_page(PGALLOC_GFP);
- if (pte) {
- clean_dcache_area(pte, sizeof(pte_t) * PTRS_PER_PTE);
- pte += PTRS_PER_PTE;
- }
+ if (pte)
+ clean_pte_table(pte);

return pte;
}
@@ -79,10 +82,8 @@ pte_alloc_one(struct mm_struct *mm, unsigned long addr)
pte = alloc_pages(PGALLOC_GFP, 0);
#endif
if (pte) {
- if (!PageHighMem(pte)) {
- void *page = page_address(pte);
- clean_dcache_area(page, sizeof(pte_t) * PTRS_PER_PTE);
- }
+ if (!PageHighMem(pte))
+ clean_pte_table(page_address(pte));
pgtable_page_ctor(pte);
}

@@ -94,10 +95,8 @@ pte_alloc_one(struct mm_struct *mm, unsigned long addr)
*/
static inline void pte_free_kernel(struct mm_struct *mm, pte_t *pte)
{
- if (pte) {
- pte -= PTRS_PER_PTE;
+ if (pte)
free_page((unsigned long)pte);
- }
}

static inline void pte_free(struct mm_struct *mm, pgtable_t pte)
@@ -106,8 +105,9 @@ static inline void pte_free(struct mm_struct *mm, pgtable_t pte)
__free_page(pte);
}

-static inline void __pmd_populate(pmd_t *pmdp, unsigned long pmdval)
+static inline void __pmd_populate(pmd_t *pmdp, unsigned long pte, unsigned long prot)
{
+ unsigned long pmdval = (pte + PTE_HWTABLE_OFF) | prot;
pmdp[0] = __pmd(pmdval);
pmdp[1] = __pmd(pmdval + 256 * sizeof(pte_t));
flush_pmd_entry(pmdp);
@@ -122,20 +122,16 @@ static inline void __pmd_populate(pmd_t *pmdp, unsigned long pmdval)
static inline void
pmd_populate_kernel(struct mm_struct *mm, pmd_t *pmdp, pte_t *ptep)
{
- unsigned long pte_ptr = (unsigned long)ptep;
-
/*
- * The pmd must be loaded with the physical
- * address of the PTE table
+ * The pmd must be loaded with the physical address of the PTE table
*/
- pte_ptr -= PTRS_PER_PTE * sizeof(void *);
- __pmd_populate(pmdp, __pa(pte_ptr) | _PAGE_KERNEL_TABLE);
+ __pmd_populate(pmdp, __pa(ptep), _PAGE_KERNEL_TABLE);
}

static inline void
pmd_populate(struct mm_struct *mm, pmd_t *pmdp, pgtable_t ptep)
{
- __pmd_populate(pmdp, page_to_pfn(ptep) << PAGE_SHIFT | _PAGE_USER_TABLE);
+ __pmd_populate(pmdp, page_to_pfn(ptep) << PAGE_SHIFT, _PAGE_USER_TABLE);
}
#define pmd_pgtable(pmd) pmd_page(pmd)

diff --git a/arch/arm/include/asm/pgtable.h b/arch/arm/include/asm/pgtable.h
index b155414..d9f1bfa 100644
--- a/arch/arm/include/asm/pgtable.h
+++ b/arch/arm/include/asm/pgtable.h
@@ -54,7 +54,7 @@
* Therefore, we tweak the implementation slightly - we tell Linux that we
* have 2048 entries in the first level, each of which is 8 bytes (iow, two
* hardware pointers to the second level.) The second level contains two
- * hardware PTE tables arranged contiguously, followed by Linux versions
+ * hardware PTE tables arranged contiguously, preceded by Linux versions
* which contain the state information Linux needs. We, therefore, end up
* with 512 entries in the "PTE" level.
*
@@ -62,15 +62,15 @@
*
* pgd pte
* | |
- * +--------+ +0
- * | |-----> +------------+ +0
+ * +--------+
+ * | | +------------+ +0
+ * +- - - - + | Linux pt 0 |
+ * | | +------------+ +1024
+ * +--------+ +0 | Linux pt 1 |
+ * | |-----> +------------+ +2048
* +- - - - + +4 | h/w pt 0 |
- * | |-----> +------------+ +1024
+ * | |-----> +------------+ +3072
* +--------+ +8 | h/w pt 1 |
- * | | +------------+ +2048
- * +- - - - + | Linux pt 0 |
- * | | +------------+ +3072
- * +--------+ | Linux pt 1 |
* | | +------------+ +4096
*
* See L_PTE_xxx below for definitions of bits in the "Linux pt", and
@@ -102,6 +102,10 @@
#define PTRS_PER_PMD 1
#define PTRS_PER_PGD 2048

+#define PTE_HWTABLE_PTRS (PTRS_PER_PTE)
+#define PTE_HWTABLE_OFF (PTE_HWTABLE_PTRS * sizeof(pte_t))
+#define PTE_HWTABLE_SIZE (PTRS_PER_PTE * sizeof(u32))
+
/*
* PMD_SHIFT determines the size of the area a second-level page table can map
* PGDIR_SHIFT determines what a third-level page table entry can map
@@ -270,8 +274,8 @@ extern struct page *empty_zero_page;
#define __pte_map(dir) pmd_page_vaddr(*(dir))
#define __pte_unmap(pte) do { } while (0)
#else
-#define __pte_map(dir) ((pte_t *)kmap_atomic(pmd_page(*(dir))) + PTRS_PER_PTE)
-#define __pte_unmap(pte) kunmap_atomic((pte - PTRS_PER_PTE))
+#define __pte_map(dir) (pte_t *)kmap_atomic(pmd_page(*(dir)))
+#define __pte_unmap(pte) kunmap_atomic(pte)
#endif

#define set_pte_ext(ptep,pte,ext) cpu_set_pte_ext(ptep,pte,ext)
@@ -364,11 +368,7 @@ extern pgprot_t phys_mem_access_prot(struct file *file, unsigned long pfn,

static inline pte_t *pmd_page_vaddr(pmd_t pmd)
{
- unsigned long ptr;
-
- ptr = pmd_val(pmd) & ~(PTRS_PER_PTE * sizeof(void *) - 1);
- ptr += PTRS_PER_PTE * sizeof(void *);
-
+ unsigned long ptr = pmd_val(pmd) & PAGE_MASK;
return __va(ptr);
}

diff --git a/arch/arm/mm/fault.c b/arch/arm/mm/fault.c
index 1e21e12..f10f9ba 100644
--- a/arch/arm/mm/fault.c
+++ b/arch/arm/mm/fault.c
@@ -108,7 +108,7 @@ void show_pte(struct mm_struct *mm, unsigned long addr)

pte = pte_offset_map(pmd, addr);
printk(", *pte=%08lx", pte_val(*pte));
- printk(", *ppte=%08lx", pte_val(pte[-PTRS_PER_PTE]));
+ printk(", *ppte=%08lx", pte_val(pte[PTE_HWTABLE_PTRS]));
pte_unmap(pte);
} while(0);

diff --git a/arch/arm/mm/mmu.c b/arch/arm/mm/mmu.c
index 72ad3e1..9963189 100644
--- a/arch/arm/mm/mmu.c
+++ b/arch/arm/mm/mmu.c
@@ -535,7 +535,7 @@ static pte_t * __init early_pte_alloc(pmd_t *pmd, unsigned long addr, unsigned l
{
if (pmd_none(*pmd)) {
pte_t *pte = early_alloc(2 * PTRS_PER_PTE * sizeof(pte_t));
- __pmd_populate(pmd, __pa(pte) | prot);
+ __pmd_populate(pmd, __pa(pte), prot);
}
BUG_ON(pmd_bad(*pmd));
return pte_offset_kernel(pmd, addr);
diff --git a/arch/arm/mm/proc-macros.S b/arch/arm/mm/proc-macros.S
index 7d63bea..cbedf9c 100644
--- a/arch/arm/mm/proc-macros.S
+++ b/arch/arm/mm/proc-macros.S
@@ -121,7 +121,7 @@
.endm

.macro armv6_set_pte_ext pfx
- str r1, [r0], #-2048 @ linux version
+ str r1, [r0], #2048 @ linux version

bic r3, r1, #0x000003fc
bic r3, r3, #PTE_TYPE_MASK
@@ -170,7 +170,7 @@
* 1111 0xff r/w r/w
*/
.macro armv3_set_pte_ext wc_disable=1
- str r1, [r0], #-2048 @ linux version
+ str r1, [r0], #2048 @ linux version

eor r3, r1, #L_PTE_PRESENT | L_PTE_YOUNG | L_PTE_WRITE | L_PTE_DIRTY

@@ -193,7 +193,7 @@
bicne r2, r2, #PTE_BUFFERABLE
#endif
.endif
- str r2, [r0] @ hardware version
+ str r2, [r0] @ hardware version
.endm


@@ -213,7 +213,7 @@
* 1111 11 r/w r/w
*/
.macro xscale_set_pte_ext_prologue
- str r1, [r0], #-2048 @ linux version
+ str r1, [r0] @ linux version

eor r3, r1, #L_PTE_PRESENT | L_PTE_YOUNG | L_PTE_WRITE | L_PTE_DIRTY

@@ -232,7 +232,7 @@
tst r3, #L_PTE_PRESENT | L_PTE_YOUNG @ present and young?
movne r2, #0 @ no -> fault

- str r2, [r0] @ hardware version
+ str r2, [r0, #2048]! @ hardware version
mov ip, #0
mcr p15, 0, r0, c7, c10, 1 @ clean L1 D line
mcr p15, 0, ip, c7, c10, 4 @ data write barrier
diff --git a/arch/arm/mm/proc-v7.S b/arch/arm/mm/proc-v7.S
index 53cbe22..89c31a6 100644
--- a/arch/arm/mm/proc-v7.S
+++ b/arch/arm/mm/proc-v7.S
@@ -124,15 +124,13 @@ ENDPROC(cpu_v7_switch_mm)
* Set a level 2 translation table entry.
*
* - ptep - pointer to level 2 translation table entry
- * (hardware version is stored at -1024 bytes)
+ * (hardware version is stored at +2048 bytes)
* - pte - PTE value to store
* - ext - value for extended PTE bits
*/
ENTRY(cpu_v7_set_pte_ext)
#ifdef CONFIG_MMU
- ARM( str r1, [r0], #-2048 ) @ linux version
- THUMB( str r1, [r0] ) @ linux version
- THUMB( sub r0, r0, #2048 )
+ str r1, [r0] @ linux version

bic r3, r1, #0x000003f0
bic r3, r3, #PTE_TYPE_MASK
@@ -158,7 +156,7 @@ ENTRY(cpu_v7_set_pte_ext)
tstne r1, #L_PTE_PRESENT
moveq r3, #0

- str r3, [r0]
+ str r3, [r0, #2048]!
mcr p15, 0, r0, c7, c10, 1 @ flush_pte
#endif
mov pc, lr


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