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m68k: mm: Improve kernel_page_table() 

With the PTE-tables now only being 256 bytes, allocating a full page
for them is a giant waste. Start by improving the boot time allocator
such that init_mm initialization will at least have optimal memory
density.

Much thanks to Will Deacon in help with debugging and ferreting out
lost information on these dusty MMUs.

Notes:

 - _TABLE_MASK is reduced to account for the shorter (256 byte)
   alignment of pte-tables, per the manual, table entries should only
   ever have state in the low 4 bits (Used,WrProt,Desc1,Desc0) so it is
   still longer than strictly required. (Thanks Will!!!)

 - Also use kernel_page_table() for the 020/030 zero_pgtable case and
   consequently remove the zero_pgtable init hack (will fix up later).

Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Acked-by: Will Deacon <will@kernel.org>
Acked-by: Greg Ungerer <gerg@linux-m68k.org>
Tested-by: Michael Schmitz <schmitzmic@gmail.com>
Tested-by: Greg Ungerer <gerg@linux-m68k.org>
Link: https://lore.kernel.org/r/20200131125403.768263973@infradead.org
Signed-off-by: Geert Uytterhoeven <geert@linux-m68k.org>
This commit is contained in:
Peter Zijlstra 2020-01-31 13:45:37 +01:00 committed by Geert Uytterhoeven
parent ef22d8abd8
commit ef9285f69f
3 changed files with 41 additions and 28 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

13
arch/m68k/include/asm/motorola_pgtable.h
View File

@ -23,7 +23,18 @@
#define _DESCTYPE_MASK 0x003
#define _CACHEMASK040 (~0x060)
#define _TABLE_MASK (0xfffffe00)
/*
* Currently set to the minimum alignment of table pointers (256 bytes).
* The hardware only uses the low 4 bits for state:
*
* 3 - Used
* 2 - Write Protected
* 0,1 - Descriptor Type
*
* and has the rest of the bits reserved.
*/
#define _TABLE_MASK (0xffffff00)
#define _PAGE_TABLE (_PAGE_SHORT)
#define _PAGE_CHG_MASK (PAGE_MASK | _PAGE_ACCESSED | _PAGE_DIRTY | _PAGE_NOCACHE)

5
arch/m68k/mm/init.c
View File

@ -42,7 +42,6 @@ EXPORT_SYMBOL(empty_zero_page);
#if !defined(CONFIG_SUN3) && !defined(CONFIG_COLDFIRE)
extern void init_pointer_table(unsigned long ptable);
extern pmd_t *zero_pgtable;
#endif
#ifdef CONFIG_MMU
@ -135,10 +134,6 @@ static inline void init_pointer_tables(void)
if (pud_present(*pud))
init_pointer_table(pgd_page_vaddr(kernel_pg_dir[i]));
}
/* insert also pointer table that we used to unmap the zero page */
if (zero_pgtable)
init_pointer_table((unsigned long)zero_pgtable);
#endif
}

51
arch/m68k/mm/motorola.c
View File

@ -174,27 +174,35 @@ extern __initdata unsigned long m68k_init_mapped_size;
extern unsigned long availmem;
static pte_t *last_pte_table __initdata = NULL;
static pte_t * __init kernel_page_table(void)
{
pte_t *ptablep;
pte_t *pte_table = last_pte_table;
ptablep = (pte_t *)memblock_alloc_low(PAGE_SIZE, PAGE_SIZE);
if (!ptablep)
panic("%s: Failed to allocate %lu bytes align=%lx\n",
__func__, PAGE_SIZE, PAGE_SIZE);
if (((unsigned long)last_pte_table & ~PAGE_MASK) == 0) {
pte_table = (pte_t *)memblock_alloc_low(PAGE_SIZE, PAGE_SIZE);
if (!pte_table) {
panic("%s: Failed to allocate %lu bytes align=%lx\n",
__func__, PAGE_SIZE, PAGE_SIZE);
}
clear_page(ptablep);
mmu_page_ctor(ptablep);
clear_page(pte_table);
mmu_page_ctor(pte_table);
return ptablep;
last_pte_table = pte_table;
}
last_pte_table += PTRS_PER_PTE;
return pte_table;
}
static pmd_t *last_pgtable __initdata = NULL;
pmd_t *zero_pgtable __initdata = NULL;
static pmd_t *last_pmd_table __initdata = NULL;
static pmd_t * __init kernel_ptr_table(void)
{
if (!last_pgtable) {
if (!last_pmd_table) {
unsigned long pmd, last;
int i;
@ -213,25 +221,25 @@ static pmd_t * __init kernel_ptr_table(void)
last = pmd;
}
last_pgtable = (pmd_t *)last;
last_pmd_table = (pmd_t *)last;
#ifdef DEBUG
printk("kernel_ptr_init: %p\n", last_pgtable);
printk("kernel_ptr_init: %p\n", last_pmd_table);
#endif
}
last_pgtable += PTRS_PER_PMD;
if (((unsigned long)last_pgtable & ~PAGE_MASK) == 0) {
last_pgtable = (pmd_t *)memblock_alloc_low(PAGE_SIZE,
last_pmd_table += PTRS_PER_PMD;
if (((unsigned long)last_pmd_table & ~PAGE_MASK) == 0) {
last_pmd_table = (pmd_t *)memblock_alloc_low(PAGE_SIZE,
PAGE_SIZE);
if (!last_pgtable)
if (!last_pmd_table)
panic("%s: Failed to allocate %lu bytes align=%lx\n",
__func__, PAGE_SIZE, PAGE_SIZE);
clear_page(last_pgtable);
mmu_page_ctor(last_pgtable);
clear_page(last_pmd_table);
mmu_page_ctor(last_pmd_table);
}
return last_pgtable;
return last_pmd_table;
}
static void __init map_node(int node)
@ -294,8 +302,7 @@ static void __init map_node(int node)
#ifdef DEBUG
printk ("[zero map]");
#endif
zero_pgtable = kernel_ptr_table();
pte_dir = (pte_t *)zero_pgtable;
pte_dir = kernel_page_table();
pmd_set(pmd_dir, pte_dir);
pte_val(*pte_dir++) = 0;