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Commit 306505cf authored by Liam Mark's avatar Liam Mark
Browse files

iommu/iova: Limit IOVA alignment using CONFIG_ARM64_DMA_IOMMU_ALIGNMENT 



Currently IOVAs are aligned to the next power of two of the size of the
allocation. This can result in unnecessary fragmentation of the IOVA
space.

If defined use CONFIG_ARM64_DMA_IOMMU_ALIGNMENT to limit the maximum IOVA
alignment.

Change-Id: Ica7f6382237e37acac2d35972a564ca1e1f5e84f
Signed-off-by: default avatarLiam Mark <lmark@codeaurora.org>
parent f0a4ec7d

drivers/iommu/iova.c

+23 −5
Original line number Diff line number Diff line
@@ -182,14 +182,28 @@ iova_insert_rbtree(struct rb_root *root, struct iova *iova, 
	rb_insert_color(&iova->node, root);

}



#ifdef CONFIG_ARM64_DMA_IOMMU_ALIGNMENT

#define MAX_ALIGN(shift) (((1 << CONFIG_ARM64_DMA_IOMMU_ALIGNMENT) * PAGE_SIZE)\

			  >> (shift))

#else

#define MAX_ALIGN(shift) ULONG_MAX

#endif



/*

 * Computes the padding size required, to make the start address

 * naturally aligned on the power-of-two order of its size

 * naturally aligned on the minimum of the power-of-two order of its size and

 * max_align

 */

static unsigned int

iova_get_pad_size(unsigned int size, unsigned int limit_pfn)

iova_get_pad_size(unsigned int size, unsigned int limit_pfn,

		  unsigned int max_align)

{

	return (limit_pfn - size) & (__roundup_pow_of_two(size) - 1);

	unsigned int align = __roundup_pow_of_two(size);



	if (align > max_align)

		align = max_align;



	return (limit_pfn - size) & (align - 1);

}



static int __alloc_and_insert_iova_range(struct iova_domain *iovad,
@@ -200,12 +214,14 @@ static int __alloc_and_insert_iova_range(struct iova_domain *iovad, 
	unsigned long flags;

	unsigned long saved_pfn;

	unsigned int pad_size = 0;

	unsigned long shift = iova_shift(iovad);



	/* Walk the tree backwards */

	spin_lock_irqsave(&iovad->iova_rbtree_lock, flags);

	saved_pfn = limit_pfn;

	curr = __get_cached_rbnode(iovad, &limit_pfn);

	prev = curr;



	while (curr) {

		struct iova *curr_iova = rb_entry(curr, struct iova, node);
@@ -213,7 +229,8 @@ static int __alloc_and_insert_iova_range(struct iova_domain *iovad, 
			goto move_left;

		} else if (limit_pfn > curr_iova->pfn_hi) {

			if (size_aligned)

				pad_size = iova_get_pad_size(size, limit_pfn);

				pad_size = iova_get_pad_size(size, limit_pfn,

							     MAX_ALIGN(shift));

			if ((curr_iova->pfn_hi + size + pad_size) < limit_pfn)

				break;	/* found a free slot */

		}
@@ -225,7 +242,8 @@ static int __alloc_and_insert_iova_range(struct iova_domain *iovad, 


	if (!curr) {

		if (size_aligned)

			pad_size = iova_get_pad_size(size, limit_pfn);

			pad_size = iova_get_pad_size(size, limit_pfn,

						     MAX_ALIGN(shift));

		if ((iovad->start_pfn + size + pad_size) > limit_pfn) {

			spin_unlock_irqrestore(&iovad->iova_rbtree_lock, flags);

			return -ENOMEM;