Messages in this thread | | | Date | Wed, 8 Jan 2003 14:44:45 -0800 | From | William Lee Irwin III <> | Subject | Re: [RFC][PATCH] allow bigger PAGE_OFFSET with PAE |
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On Tue, Jan 07, 2003 at 12:06:38PM -0800, Dave Hansen wrote: >>>> Also, this gets the kernel's pagetables right, but neglects >>>> userspace's for now. pgd_alloc() needs to be fixed to allocate >>>> another PMD, if the split isn't PMD-alighed.
William Lee Irwin III wrote: >>> Um, that should be automatic when USER_PTRS_PER_PGD is increased.
On Wed, Jan 08, 2003 at 01:04:23PM -0800, Dave Hansen wrote: >> Nope, you need a little bit more. pgd_alloc() relies on its memcpy() >> to provide the kernel mappings. After the last user PMD is allocated, >> you still need to copy the kernel-shared part of it in.
On Wed, Jan 08, 2003 at 02:05:33PM -0800, William Lee Irwin III wrote: > See the bit about rounding up. Then again, the pmd entries don't get > filled in by any of that...
Okay, basically:
#define __USER_PTRS_PER_PGD (TASK_SIZE/PGDIR_SIZE) #define PARTIAL_PGD (TASK_SIZE > __USER_PTRS_PER_PGD*PGDIR_SIZE ? 1 : 0) #define PARTIAL_PMD ((TASK_SIZE % PGDIR_SIZE)/PMD_SIZE) #define USER_PTRS_PER_PGD (PARTIAL_PGD + __USER_PTRS_PER_PGD)
then
pgd_t *pgd_alloc(struct mm_struct *mm) { int i; pgd_t *pgd = kmem_cache_alloc(pae_pgd_cachep, GFP_KERNEL);
if (pgd) { for (i = 0; i < USER_PTRS_PER_PGD; i++) { unsigned long pmd = __get_free_page(GFP_KERNEL); if (!pmd) goto out_oom; clear_page(pmd); set_pgd(pgd + i, __pgd(1 + __pa(pmd))); }
if (USER_PTRS_PER_PGD < PTRS_PER_PGD) memcpy(pgd + USER_PTRS_PER_PGD, swapper_pg_dir + USER_PTRS_PER_PGD, (PTRS_PER_PGD-USER_PTRS_PER_PGD)*sizeof(pgd_t));
if (PARTIAL_PGD) { pgd_t *kpgd, *upgd; pmd_t *kpmd, *upmd;
kpgd = pgd_offset_k(TASK_SIZE); upgd = pgd_offset(mm, TASK_SIZE); kpmd = pmd_offset(kpgd, TASK_SIZE); upmd = pmd_offset(upgd, TASK_SIZE);
memcpy(upmd, kpmd, (PTRS_PER_PMD-PARTIAL_PMD)*sizeof(pmd_t));
} } return pgd; out_oom: for (i--; i >= 0; i--) free_page((unsigned long)__va(pgd_val(pgd[i])-1)); kmem_cache_free(pae_pgd_cachep, pgd); return NULL; }
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