[PATCH -v2 05/10] m68k,mm: Restructure Motorola MMU page-table layout

Peter Zijlstra
2020-01-31T12:56:08Z

The Motorola 68xxx MMUs, 040 (and later) have a fixed 7,7,{5,6}
page-table setup, where the last depends on the page-size selected (8k
vs 4k resp.), and head.S selects 4K pages. For 030 (and earlier) we
explicitly program 7,7,6 and 4K pages in %tc.

However, the current code implements this mightily weird. What it does
is group 16 of those (6 bit) pte tables into one 4k page to not waste
space. The down-side is that that forces pmd_t to be a 16-tuple
pointing to consecutive pte tables.

This breaks the generic code which assumes READ_ONCE(*pmd) will be
word sized.

Therefore implement a straight forward 7,7,6 3 level page-table setup,
with the addition (for 020/030) of (partial) large-page support. For
now this increases the memory footprint for pte-tables 15 fold.

Tested with ARAnyM/68040 emulation.

Suggested-by: Will Deacon <will@kernel.org>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
---
arch/m68k/include/asm/motorola_pgtable.h | 15 +-----------
arch/m68k/include/asm/page.h | 6 ++---
arch/m68k/include/asm/pgtable_mm.h | 10 ++++----
arch/m68k/mm/kmap.c | 36 +++++++++++++------------------
arch/m68k/mm/motorola.c | 28 +++++++++++-------------
5 files changed, 39 insertions(+), 56 deletions(-)

--- a/arch/m68k/include/asm/motorola_pgtable.h
+++ b/arch/m68k/include/asm/motorola_pgtable.h
@@ -108,13 +108,7 @@ static inline pte_t pte_modify(pte_t pte

static inline void pmd_set(pmd_t *pmdp, pte_t *ptep)
{
- unsigned long ptbl = virt_to_phys(ptep) | _PAGE_TABLE | _PAGE_ACCESSED;
- unsigned long *ptr = pmdp->pmd;
- short i = 16;
- while (--i >= 0) {
- *ptr++ = ptbl;
- ptbl += (sizeof(pte_t)*PTRS_PER_PTE/16);
- }
+ pmd_val(*pmdp) = virt_to_phys(ptep) | _PAGE_TABLE | _PAGE_ACCESSED;
}

static inline void pud_set(pud_t *pudp, pmd_t *pmdp)
@@ -138,12 +132,7 @@ static inline void pud_set(pud_t *pudp,
#define pmd_none(pmd) (!pmd_val(pmd))
#define pmd_bad(pmd) ((pmd_val(pmd) & _DESCTYPE_MASK) != _PAGE_TABLE)
#define pmd_present(pmd) (pmd_val(pmd) & _PAGE_TABLE)
-#define pmd_clear(pmdp) ({ \
- unsigned long *__ptr = pmdp->pmd; \
- short __i = 16; \
- while (--__i >= 0) \
- *__ptr++ = 0; \
-})
+#define pmd_clear(pmdp) ({ pmd_val(*pmdp) = 0; })
#define pmd_page(pmd) virt_to_page(__va(pmd_val(pmd)))

--- a/arch/m68k/include/asm/page.h
+++ b/arch/m68k/include/asm/page.h
@@ -22,9 +22,9 @@
* These are used to make use of C type-checking..
*/
#if !defined(CONFIG_MMU) || CONFIG_PGTABLE_LEVELS == 3
-typedef struct { unsigned long pmd[16]; } pmd_t;
-#define pmd_val(x) ((&x)->pmd[0])
-#define __pmd(x) ((pmd_t) { { (x) }, })
+typedef struct { unsigned long pmd; } pmd_t;
+#define pmd_val(x) ((&x)->pmd)
+#define __pmd(x) ((pmd_t) { (x) } )
#endif

typedef struct { unsigned long pte; } pte_t;
--- a/arch/m68k/include/asm/pgtable_mm.h
+++ b/arch/m68k/include/asm/pgtable_mm.h
@@ -36,7 +36,7 @@

/* PMD_SHIFT determines the size of the area a second-level page table can map */
#if CONFIG_PGTABLE_LEVELS == 3
-#define PMD_SHIFT 22
+#define PMD_SHIFT 18
#endif
#define PMD_SIZE (1UL << PMD_SHIFT)
#define PMD_MASK (~(PMD_SIZE-1))
@@ -67,8 +67,8 @@
#define PTRS_PER_PMD 1
#define PTRS_PER_PGD 1024
#else
-#define PTRS_PER_PTE 1024
-#define PTRS_PER_PMD 8
+#define PTRS_PER_PTE 64
+#define PTRS_PER_PMD 128
#define PTRS_PER_PGD 128
#endif
#define USER_PTRS_PER_PGD (TASK_SIZE/PGDIR_SIZE)
@@ -76,8 +76,8 @@

/* Virtual address region for use by kernel_map() */
#ifdef CONFIG_SUN3
-#define KMAP_START 0x0DC00000
-#define KMAP_END 0x0E000000
+#define KMAP_START 0x0dc00000
+#define KMAP_END 0x0e000000
#elif defined(CONFIG_COLDFIRE)
#define KMAP_START 0xe0000000
#define KMAP_END 0xf0000000
--- a/arch/m68k/mm/kmap.c
+++ b/arch/m68k/mm/kmap.c
@@ -24,8 +24,6 @@

#undef DEBUG

-#define PTRTREESIZE (256*1024)
-
/*
* For 040/060 we can use the virtual memory area like other architectures,
* but for 020/030 we want to use early termination page descriptors and we
@@ -50,7 +48,7 @@ static inline void free_io_area(void *ad

#else

-#define IO_SIZE (256*1024)
+#define IO_SIZE PMD_SIZE

static struct vm_struct *iolist;

@@ -81,14 +79,13 @@ static void __free_io_area(void *addr, u

#if CONFIG_PGTABLE_LEVELS == 3
if (CPU_IS_020_OR_030) {
- int pmd_off = (virtaddr/PTRTREESIZE) & 15;
- int pmd_type = pmd_dir->pmd[pmd_off] & _DESCTYPE_MASK;
+ int pmd_type = pmd_val(*pmd_dir) & _DESCTYPE_MASK;

if (pmd_type == _PAGE_PRESENT) {
- pmd_dir->pmd[pmd_off] = 0;
- virtaddr += PTRTREESIZE;
- size -= PTRTREESIZE;
- continue;
+ pmd_clear(pmd_dir);
+ virtaddr += PMD_SIZE;
+ size -= PMD_SIZE;
+
} else if (pmd_type == 0)
continue;
}
@@ -249,7 +246,7 @@ void __iomem *__ioremap(unsigned long ph

while ((long)size > 0) {
#ifdef DEBUG
- if (!(virtaddr & (PTRTREESIZE-1)))
+ if (!(virtaddr & (PMD_SIZE-1)))
printk ("\npa=%#lx va=%#lx ", physaddr, virtaddr);
#endif
pgd_dir = pgd_offset_k(virtaddr);
@@ -263,10 +260,10 @@ void __iomem *__ioremap(unsigned long ph

#if CONFIG_PGTABLE_LEVELS == 3
if (CPU_IS_020_OR_030) {
- pmd_dir->pmd[(virtaddr/PTRTREESIZE) & 15] = physaddr;
- physaddr += PTRTREESIZE;
- virtaddr += PTRTREESIZE;
- size -= PTRTREESIZE;
+ pmd_val(*pmd_dir) = physaddr;
+ physaddr += PMD_SIZE;
+ virtaddr += PMD_SIZE;
+ size -= PMD_SIZE;
} else
#endif
{
@@ -367,13 +364,12 @@ void kernel_set_cachemode(void *addr, un

#if CONFIG_PGTABLE_LEVELS == 3
if (CPU_IS_020_OR_030) {
- int pmd_off = (virtaddr/PTRTREESIZE) & 15;
+ unsigned long pmd = pmd_val(*pmd_dir);

- if ((pmd_dir->pmd[pmd_off] & _DESCTYPE_MASK) == _PAGE_PRESENT) {
- pmd_dir->pmd[pmd_off] = (pmd_dir->pmd[pmd_off] &
- _CACHEMASK040) | cmode;
- virtaddr += PTRTREESIZE;
- size -= PTRTREESIZE;
+ if ((pmd & _DESCTYPE_MASK) == _PAGE_PRESENT) {
+ *pmd_dir = __pmd((pmd & _CACHEMASK040) | cmode);
+ virtaddr += PMD_SIZE;
+ size -= PMD_SIZE;
continue;
}
}
--- a/arch/m68k/mm/motorola.c
+++ b/arch/m68k/mm/motorola.c
@@ -236,8 +236,6 @@ static pmd_t * __init kernel_ptr_table(v

static void __init map_node(int node)
{
-#define PTRTREESIZE (256*1024)
-#define ROOTTREESIZE (32*1024*1024)
unsigned long physaddr, virtaddr, size;
pgd_t *pgd_dir;
p4d_t *p4d_dir;
@@ -255,21 +253,21 @@ static void __init map_node(int node)

while (size > 0) {
#ifdef DEBUG
- if (!(virtaddr & (PTRTREESIZE-1)))
+ if (!(virtaddr & (PMD_SIZE-1)))
printk ("\npa=%#lx va=%#lx ", physaddr & PAGE_MASK,
virtaddr);
#endif
pgd_dir = pgd_offset_k(virtaddr);
if (virtaddr && CPU_IS_020_OR_030) {
- if (!(virtaddr & (ROOTTREESIZE-1)) &&
- size >= ROOTTREESIZE) {
+ if (!(virtaddr & (PGDIR_SIZE-1)) &&
+ size >= PGDIR_SIZE) {
#ifdef DEBUG
printk ("[very early term]");
#endif
pgd_val(*pgd_dir) = physaddr;
- size -= ROOTTREESIZE;
- virtaddr += ROOTTREESIZE;
- physaddr += ROOTTREESIZE;
+ size -= PGDIR_SIZE;
+ virtaddr += PGDIR_SIZE;
+ physaddr += PGDIR_SIZE;
continue;
}
}
@@ -289,8 +287,8 @@ static void __init map_node(int node)
#ifdef DEBUG
printk ("[early term]");
#endif
- pmd_dir->pmd[(virtaddr/PTRTREESIZE) & 15] = physaddr;
- physaddr += PTRTREESIZE;
+ pmd_val(*pmd_dir) = physaddr;
+ physaddr += PMD_SIZE;
} else {
int i;
#ifdef DEBUG
@@ -298,15 +296,15 @@ static void __init map_node(int node)
#endif
zero_pgtable = kernel_ptr_table();
pte_dir = (pte_t *)zero_pgtable;
- pmd_dir->pmd[0] = virt_to_phys(pte_dir) |
- _PAGE_TABLE | _PAGE_ACCESSED;
+ pmd_set(pmd_dir, pte_dir);
+
pte_val(*pte_dir++) = 0;
physaddr += PAGE_SIZE;
- for (i = 1; i < 64; physaddr += PAGE_SIZE, i++)
+ for (i = 1; i < PTRS_PER_PTE; physaddr += PAGE_SIZE, i++)
pte_val(*pte_dir++) = physaddr;
}
- size -= PTRTREESIZE;
- virtaddr += PTRTREESIZE;
+ size -= PMD_SIZE;
+ virtaddr += PMD_SIZE;
} else {
if (!pmd_present(*pmd_dir)) {
#ifdef DEBUG