arm64: Align less than PAGE_SIZE pgds naturally (2a0b5c0d) · Commits · 戴 / test

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:

Christoffer Dall <christoffer.dall@linaro.org> Reviewed-by:

Christoffer Dall <christoffer.dall@linaro.org> Signed-off-by:

Catalin Marinas <catalin.marinas@arm.com>

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);

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