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Commit 2a0b5c0d authored by Catalin Marinas's avatar Catalin Marinas
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arm64: Align less than PAGE_SIZE pgds naturally 



When the pgd size is smaller than PAGE_SIZE, pgd_alloc() uses kzalloc()
to save space. However, this is not always naturally aligned as required
by the architecture. This patch creates a kmem_cache for pgd allocations
with the correct alignment.

The current kernel configurations with 4K pages + 39-bit VA and 64K
pages + 42-bit VA use a full page for the pgd and are not affected. The
patch is required for 48-bit VA with 64K pages where the pgd is 512
bytes.

Reported-by: default avatarChristoffer Dall <christoffer.dall@linaro.org>
Reviewed-by: default avatarChristoffer Dall <christoffer.dall@linaro.org>
Signed-off-by: default avatarCatalin Marinas <catalin.marinas@arm.com>
parent 04f905a9

arch/arm64/mm/pgd.c

+16 −2
Original line number Diff line number Diff line
@@ -30,12 +30,14 @@ 


#define PGD_SIZE	(PTRS_PER_PGD * sizeof(pgd_t))



static struct kmem_cache *pgd_cache;



pgd_t *pgd_alloc(struct mm_struct *mm)

{

	if (PGD_SIZE == PAGE_SIZE)

		return (pgd_t *)get_zeroed_page(GFP_KERNEL);

	else

		return kzalloc(PGD_SIZE, GFP_KERNEL);

		return kmem_cache_zalloc(pgd_cache, GFP_KERNEL);

}



void pgd_free(struct mm_struct *mm, pgd_t *pgd)
@@ -43,5 +45,17 @@ void pgd_free(struct mm_struct *mm, pgd_t *pgd) 
	if (PGD_SIZE == PAGE_SIZE)

		free_page((unsigned long)pgd);

	else

		kfree(pgd);

		kmem_cache_free(pgd_cache, pgd);

}



static int __init pgd_cache_init(void)

{

	/*

	 * Naturally aligned pgds required by the architecture.

	 */

	if (PGD_SIZE != PAGE_SIZE)

		pgd_cache = kmem_cache_create("pgd_cache", PGD_SIZE, PGD_SIZE,

					      SLAB_PANIC, NULL);

	return 0;

}

core_initcall(pgd_cache_init);