Re: [PATCHv6 7/7] ARM: dma-mapping: add support for IOMMU mapper

[Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>]

> +static void __dma_clear_buffer(struct page *page, size_t size)
> +{
> +	void *ptr;
> +	/*
> +	 * Ensure that the allocated pages are zeroed, and that any data
> +	 * lurking in the kernel direct-mapped region is invalidated.
> +	 */
> +	ptr = page_address(page);

Should you check to see if the ptr is valid?

> +	memset(ptr, 0, size);
> +	dmac_flush_range(ptr, ptr + size);
> +	outer_flush_range(__pa(ptr), __pa(ptr) + size);
> +}
> +
>  /*
>   * Allocate a DMA buffer for 'dev' of size 'size' using the
>   * specified gfp mask.  Note that 'size' must be page aligned.
> @@ -164,7 +179,6 @@ static struct page *__dma_alloc_buffer(struct device *dev, size_t size, gfp_t gf
>  {
>  	unsigned long order = get_order(size);
>  	struct page *page, *p, *e;
> -	void *ptr;
>  	u64 mask = get_coherent_dma_mask(dev);
>  
>  #ifdef CONFIG_DMA_API_DEBUG
> @@ -193,14 +207,7 @@ static struct page *__dma_alloc_buffer(struct device *dev, size_t size, gfp_t gf
>  	for (p = page + (size >> PAGE_SHIFT), e = page + (1 << order); p < e; p++)
>  		__free_page(p);
>  
> -	/*
> -	 * Ensure that the allocated pages are zeroed, and that any data
> -	 * lurking in the kernel direct-mapped region is invalidated.
> -	 */
> -	ptr = page_address(page);
> -	memset(ptr, 0, size);
> -	dmac_flush_range(ptr, ptr + size);
> -	outer_flush_range(__pa(ptr), __pa(ptr) + size);
> +	__dma_clear_buffer(page, size);
>  
>  	return page;
>  }
> @@ -348,7 +355,7 @@ __dma_alloc_remap(struct page *page, size_t size, gfp_t gfp, pgprot_t prot)
>  		u32 off = CONSISTENT_OFFSET(c->vm_start) & (PTRS_PER_PTE-1);
>  
>  		pte = consistent_pte[idx] + off;
> -		c->vm_pages = page;
> +		c->priv = page;
>  
>  		do {
>  			BUG_ON(!pte_none(*pte));
> @@ -461,6 +468,14 @@ __dma_alloc(struct device *dev, size_t size, dma_addr_t *handle, gfp_t gfp,
>  	return addr;
>  }
>  
> +static inline pgprot_t __get_dma_pgprot(struct dma_attrs *attrs, pgprot_t prot)
> +{
> +	prot = dma_get_attr(DMA_ATTR_WRITE_COMBINE, attrs) ?
> +			    pgprot_writecombine(prot) :
> +			    pgprot_dmacoherent(prot);
> +	return prot;
> +}
> +
>  /*
>   * Allocate DMA-coherent memory space and return both the kernel remapped
>   * virtual and bus address for that space.
> @@ -468,9 +483,7 @@ __dma_alloc(struct device *dev, size_t size, dma_addr_t *handle, gfp_t gfp,
>  void *arm_dma_alloc(struct device *dev, size_t size, dma_addr_t *handle,
>  		    gfp_t gfp, struct dma_attrs *attrs)
>  {
> -	pgprot_t prot = dma_get_attr(DMA_ATTR_WRITE_COMBINE, attrs) ?
> -			pgprot_writecombine(pgprot_kernel) :
> -			pgprot_dmacoherent(pgprot_kernel);
> +	pgprot_t prot = __get_dma_pgprot(attrs, pgprot_kernel);
>  	void *memory;
>  
>  	if (dma_alloc_from_coherent(dev, size, handle, &memory))
> @@ -499,13 +512,14 @@ int arm_dma_mmap(struct device *dev, struct vm_area_struct *vma,
>  	c = arm_vmregion_find(&consistent_head, (unsigned long)cpu_addr);
>  	if (c) {
>  		unsigned long off = vma->vm_pgoff;
> +		struct page *pages = c->priv;
>  
>  		kern_size = (c->vm_end - c->vm_start) >> PAGE_SHIFT;
>  
>  		if (off < kern_size &&
>  		    user_size <= (kern_size - off)) {
>  			ret = remap_pfn_range(vma, vma->vm_start,
> -					      page_to_pfn(c->vm_pages) + off,
> +					      page_to_pfn(pages) + off,
>  					      user_size << PAGE_SHIFT,
>  					      vma->vm_page_prot);
>  		}
> @@ -644,6 +658,9 @@ int arm_dma_map_sg(struct device *dev, struct scatterlist *sg, int nents,
>  	int i, j;
>  
>  	for_each_sg(sg, s, nents, i) {
> +#ifdef CONFIG_NEED_SG_DMA_LENGTH
> +		s->dma_length = s->length;
> +#endif
>  		s->dma_address = ops->map_page(dev, sg_page(s), s->offset,
>  						s->length, dir, attrs);
>  		if (dma_mapping_error(dev, s->dma_address))
> @@ -749,3 +766,593 @@ static int __init dma_debug_do_init(void)
>  	return 0;
>  }
>  fs_initcall(dma_debug_do_init);
> +
> +#ifdef CONFIG_ARM_DMA_USE_IOMMU
> +
> +/* IOMMU */
> +
> +static inline dma_addr_t __alloc_iova(struct dma_iommu_mapping *mapping,
> +				      size_t size)
> +{
> +	unsigned int order = get_order(size);
> +	unsigned int align = 0;
> +	unsigned int count, start;
> +	unsigned long flags;
> +
> +	count = ((PAGE_ALIGN(size) >> PAGE_SHIFT) +
> +		 (1 << mapping->order) - 1) >> mapping->order;
> +
> +	if (order > mapping->order)
> +		align = (1 << (order - mapping->order)) - 1;
> +
> +	spin_lock_irqsave(&mapping->lock, flags);
> +	start = bitmap_find_next_zero_area(mapping->bitmap, mapping->bits, 0,
> +					   count, align);
> +	if (start > mapping->bits) {
> +		spin_unlock_irqrestore(&mapping->lock, flags);
> +		return ~0;

Would it make sense to use DMA_ERROR_CODE? Or a ARM variant of it.

> +	}
> +
> +	bitmap_set(mapping->bitmap, start, count);
> +	spin_unlock_irqrestore(&mapping->lock, flags);
> +
> +	return mapping->base + (start << (mapping->order + PAGE_SHIFT));
> +}
> +
> +static inline void __free_iova(struct dma_iommu_mapping *mapping,
> +			       dma_addr_t addr, size_t size)
> +{
> +	unsigned int start = (addr - mapping->base) >>
> +			     (mapping->order + PAGE_SHIFT);
> +	unsigned int count = ((size >> PAGE_SHIFT) +
> +			      (1 << mapping->order) - 1) >> mapping->order;
> +	unsigned long flags;
> +
> +	spin_lock_irqsave(&mapping->lock, flags);
> +	bitmap_clear(mapping->bitmap, start, count);
> +	spin_unlock_irqrestore(&mapping->lock, flags);
> +}
> +
> +static struct page **__iommu_alloc_buffer(struct device *dev, size_t size, gfp_t gfp)
> +{
> +	struct page **pages;
> +	int count = size >> PAGE_SHIFT;
> +	int i=0;
> +
> +	pages = kzalloc(count * sizeof(struct page*), gfp);
> +	if (!pages)
> +		return NULL;
> +
> +	while (count) {
> +		int j, order = __ffs(count);
> +
> +		pages[i] = alloc_pages(gfp | __GFP_NOWARN, order);
> +		while (!pages[i] && order)
> +			pages[i] = alloc_pages(gfp | __GFP_NOWARN, --order);
> +		if (!pages[i])
> +			goto error;
> +
> +		if (order)
> +			split_page(pages[i], order);
> +		j = 1 << order;
> +		while (--j)
> +			pages[i + j] = pages[i] + j;
> +
> +		__dma_clear_buffer(pages[i], PAGE_SIZE << order);
> +		i += 1 << order;
> +		count -= 1 << order;
> +	}
> +
> +	return pages;
> +error:
> +	while (--i)
> +		if (pages[i])
> +			__free_pages(pages[i], 0);
> +	kfree(pages);
> +	return NULL;
> +}
> +
> +static int __iommu_free_buffer(struct device *dev, struct page **pages, size_t size)
> +{
> +	int count = size >> PAGE_SHIFT;
> +	int i;
> +	for (i=0; i< count; i++)

That 'i< count' looks odd. Did checkpath miss that one?

> +		if (pages[i])
> +			__free_pages(pages[i], 0);
> +	kfree(pages);
> +	return 0;
> +}
> +
> +static void *
> +__iommu_alloc_remap(struct page **pages, size_t size, gfp_t gfp, pgprot_t prot)
> +{
> +	struct arm_vmregion *c;
> +	size_t align;
> +	size_t count = size >> PAGE_SHIFT;
> +	int bit;
> +
> +	if (!consistent_pte[0]) {
> +		printk(KERN_ERR "%s: not initialised\n", __func__);
> +		dump_stack();
> +		return NULL;
> +	}
> +
> +	/*
> +	 * Align the virtual region allocation - maximum alignment is
> +	 * a section size, minimum is a page size.  This helps reduce
> +	 * fragmentation of the DMA space, and also prevents allocations
> +	 * smaller than a section from crossing a section boundary.
> +	 */
> +	bit = fls(size - 1);
> +	if (bit > SECTION_SHIFT)
> +		bit = SECTION_SHIFT;
> +	align = 1 << bit;
> +
> +	/*
> +	 * Allocate a virtual address in the consistent mapping region.
> +	 */
> +	c = arm_vmregion_alloc(&consistent_head, align, size,
> +			    gfp & ~(__GFP_DMA | __GFP_HIGHMEM));
> +	if (c) {
> +		pte_t *pte;
> +		int idx = CONSISTENT_PTE_INDEX(c->vm_start);
> +		int i = 0;
> +		u32 off = CONSISTENT_OFFSET(c->vm_start) & (PTRS_PER_PTE-1);
> +
> +		pte = consistent_pte[idx] + off;
> +		c->priv = pages;
> +
> +		do {
> +			BUG_ON(!pte_none(*pte));
> +
> +			set_pte_ext(pte, mk_pte(pages[i], prot), 0);
> +			pte++;
> +			off++;
> +			i++;
> +			if (off >= PTRS_PER_PTE) {
> +				off = 0;
> +				pte = consistent_pte[++idx];
> +			}
> +		} while (i < count);
> +
> +		dsb();
> +
> +		return (void *)c->vm_start;
> +	}
> +	return NULL;
> +}
> +
> +static dma_addr_t __iommu_create_mapping(struct device *dev, struct page **pages, size_t size)
> +{
> +	struct dma_iommu_mapping *mapping = dev->archdata.mapping;
> +	unsigned int count = PAGE_ALIGN(size) >> PAGE_SHIFT;
> +	dma_addr_t dma_addr, iova;
> +	int i, ret = ~0;
> +
> +	dma_addr = __alloc_iova(mapping, size);
> +	if (dma_addr == ~0)
> +		goto fail;
> +
> +	iova = dma_addr;
> +	for (i=0; i<count; ) {
> +		unsigned int phys = page_to_phys(pages[i]);

phys_addr_t ?

> +		int j = i + 1;
> +
> +		while (j < count) {
> +			if (page_to_phys(pages[j]) != phys + (j - i) * PAGE_SIZE)
> +				break;

How about just using pfn values?
So:

	unsigned int next_pfn = page_to_pfn(pages[i])
	unsigned int pfn = i;

	for (j = 1; j < count; j++)
		if (page_to_pfn(pages[++pfn]) != ++next_pfn)
			break;

IMHO it looks easier to read.

> +			j++;
> +		}
> +
> +		ret = iommu_map(mapping->domain, iova, phys, (j - i) * PAGE_SIZE, 0);
> +		if (ret < 0)
> +			goto fail;
> +		iova += (j - i) * PAGE_SIZE;
> +		i = j;

Granted you would have to rework this a bit.
> +	}
> +
> +	return dma_addr;
> +fail:
> +	return ~0;

DMA_ERROR_CODE

> +}
> +
> +static int __iommu_remove_mapping(struct device *dev, dma_addr_t iova, size_t size)
> +{
> +	struct dma_iommu_mapping *mapping = dev->archdata.mapping;
> +	unsigned int count = PAGE_ALIGN(size) >> PAGE_SHIFT;
> +
> +	iova &= PAGE_MASK;
> +
> +	iommu_unmap(mapping->domain, iova, count * PAGE_SIZE);
> +
> +	__free_iova(mapping, iova, size);
> +	return 0;
> +}
> +
> +static void *arm_iommu_alloc_attrs(struct device *dev, size_t size,
> +	    dma_addr_t *handle, gfp_t gfp, struct dma_attrs *attrs)
> +{
> +	pgprot_t prot = __get_dma_pgprot(attrs, pgprot_kernel);
> +	struct page **pages;
> +	void *addr = NULL;
> +
> +	*handle = ~0;
> +	size = PAGE_ALIGN(size);
> +
> +	pages = __iommu_alloc_buffer(dev, size, gfp);
> +	if (!pages)
> +		return NULL;
> +
> +	*handle = __iommu_create_mapping(dev, pages, size);
> +	if (*handle == ~0)
> +		goto err_buffer;
> +
> +	addr = __iommu_alloc_remap(pages, size, gfp, prot);
> +	if (!addr)
> +		goto err_mapping;
> +
> +	return addr;
> +
> +err_mapping:
> +	__iommu_remove_mapping(dev, *handle, size);
> +err_buffer:
> +	__iommu_free_buffer(dev, pages, size);
> +	return NULL;
> +}
> +
> +static int arm_iommu_mmap_attrs(struct device *dev, struct vm_area_struct *vma,
> +		    void *cpu_addr, dma_addr_t dma_addr, size_t size,
> +		    struct dma_attrs *attrs)
> +{
> +	struct arm_vmregion *c;
> +
> +	vma->vm_page_prot = __get_dma_pgprot(attrs, vma->vm_page_prot);
> +	c = arm_vmregion_find(&consistent_head, (unsigned long)cpu_addr);
> +
> +	if (c) {
> +		struct page **pages = c->priv;
> +
> +		unsigned long uaddr = vma->vm_start;
> +		unsigned long usize = vma->vm_end - vma->vm_start;
> +		int i = 0;
> +
> +		do {
> +			int ret;
> +
> +			ret = vm_insert_page(vma, uaddr, pages[i++]);
> +			if (ret) {
> +				printk(KERN_ERR "Remapping memory, error: %d\n", ret);
> +				return ret;
> +			}
> +
> +			uaddr += PAGE_SIZE;
> +			usize -= PAGE_SIZE;
> +		} while (usize > 0);
> +	}
> +	return 0;
> +}
> +
> +/*
> + * free a page as defined by the above mapping.
> + * Must not be called with IRQs disabled.
> + */
> +void arm_iommu_free_attrs(struct device *dev, size_t size, void *cpu_addr,
> +			  dma_addr_t handle, struct dma_attrs *attrs)
> +{
> +	struct arm_vmregion *c;
> +	size = PAGE_ALIGN(size);
> +
> +	c = arm_vmregion_find(&consistent_head, (unsigned long)cpu_addr);
> +	if (c) {
> +		struct page **pages = c->priv;
> +		__dma_free_remap(cpu_addr, size);
> +		__iommu_remove_mapping(dev, handle, size);
> +		__iommu_free_buffer(dev, pages, size);
> +	}
> +}
> +
> +static int __map_sg_chunk(struct device *dev, struct scatterlist *sg,
> +			  size_t size, dma_addr_t *handle,
> +			  enum dma_data_direction dir)
> +{
> +	struct dma_iommu_mapping *mapping = dev->archdata.mapping;
> +	dma_addr_t iova, iova_base;
> +	int ret = 0;
> +	unsigned int count;
> +	struct scatterlist *s;
> +
> +	size = PAGE_ALIGN(size);
> +	*handle = ~0;
> +
> +	iova_base = iova = __alloc_iova(mapping, size);
> +	if (iova == ~0)
> +		return -ENOMEM;
> +
> +	for (count = 0, s = sg; count < (size >> PAGE_SHIFT); s = sg_next(s))
> +	{
> +		phys_addr_t phys = page_to_phys(sg_page(s));
> +		unsigned int len = PAGE_ALIGN(s->offset + s->length);
> +
> +		if (!arch_is_coherent())
> +			__dma_page_cpu_to_dev(sg_page(s), s->offset, s->length, dir);
> +
> +		ret = iommu_map(mapping->domain, iova, phys, len, 0);
> +		if (ret < 0)
> +			goto fail;
> +		count += len >> PAGE_SHIFT;
> +		iova += len;
> +	}
> +	*handle = iova_base;
> +
> +	return 0;
> +fail:
> +	iommu_unmap(mapping->domain, iova_base, count * PAGE_SIZE);
> +	__free_iova(mapping, iova_base, size);
> +	return ret;
> +}
> +
> +int arm_iommu_map_sg(struct device *dev, struct scatterlist *sg, int nents,
> +		     enum dma_data_direction dir, struct dma_attrs *attrs)
> +{
> +	struct scatterlist *s = sg, *dma = sg, *start = sg;
> +	int i, count = 0;
> +	unsigned int offset = s->offset;
> +	unsigned int size = s->offset + s->length;
> +	unsigned int max = dma_get_max_seg_size(dev);
> +
> +	s->dma_address = ~0;
> +	s->dma_length = 0;

Not zero just in case somebody does not check the values and tries to use them?
> +
> +	for (i = 1; i < nents; i++) {
> +		s->dma_address = ~0;
> +		s->dma_length = 0;
> +
> +		s = sg_next(s);
> +
> +		if (s->offset || (size & ~PAGE_MASK) || size + s->length > max) {
> +			if (__map_sg_chunk(dev, start, size, &dma->dma_address,
> +			    dir) < 0)
> +				goto bad_mapping;
> +
> +			dma->dma_address += offset;
> +			dma->dma_length = size - offset;
> +
> +			size = offset = s->offset;
> +			start = s;
> +			dma = sg_next(dma);
> +			count += 1;
> +		}
> +		size += s->length;
> +	}
> +	if (__map_sg_chunk(dev, start, size, &dma->dma_address, dir) < 0)
> +		goto bad_mapping;
> +
> +	dma->dma_address += offset;
> +	dma->dma_length = size - offset;
> +
> +	return count+1;
> +
> +bad_mapping:
> +	for_each_sg(sg, s, count, i)
> +		__iommu_remove_mapping(dev, sg_dma_address(s), sg_dma_len(s));
> +	return 0;
> +}
> +
> +void arm_iommu_unmap_sg(struct device *dev, struct scatterlist *sg, int nents,
> +			enum dma_data_direction dir, struct dma_attrs *attrs)
> +{
> +	struct scatterlist *s;
> +	int i;
> +
> +	for_each_sg(sg, s, nents, i) {
> +		if (sg_dma_len(s))
> +			__iommu_remove_mapping(dev, sg_dma_address(s),
> +					       sg_dma_len(s));
> +		if (!arch_is_coherent())
> +			__dma_page_dev_to_cpu(sg_page(s), s->offset,
> +					      s->length, dir);
> +	}
> +}
> +
> +
> +/**
> + * dma_sync_sg_for_cpu
> + * @dev: valid struct device pointer, or NULL for ISA and EISA-like devices

Uhhh, Won't that conflict with patch #1 which BUGs if dev != NULL?

> + * @sg: list of buffers
> + * @nents: number of buffers to map (returned from dma_map_sg)
> + * @dir: DMA transfer direction (same as was passed to dma_map_sg)
> + */
> +void arm_iommu_sync_sg_for_cpu(struct device *dev, struct scatterlist *sg,
> +			int nents, enum dma_data_direction dir)
> +{
> +	struct scatterlist *s;
> +	int i;
> +
> +	for_each_sg(sg, s, nents, i)
> +		if (!arch_is_coherent())
> +			__dma_page_dev_to_cpu(sg_page(s), s->offset, s->length, dir);

Uh, I thought you would need to pass in the 'dev'?

> +
> +}
> +
> +/**
> + * dma_sync_sg_for_device
> + * @dev: valid struct device pointer, or NULL for ISA and EISA-like devices
> + * @sg: list of buffers
> + * @nents: number of buffers to map (returned from dma_map_sg)
> + * @dir: DMA transfer direction (same as was passed to dma_map_sg)
> + */
> +void arm_iommu_sync_sg_for_device(struct device *dev, struct scatterlist *sg,
> +			int nents, enum dma_data_direction dir)
> +{
> +	struct scatterlist *s;
> +	int i;
> +
> +	for_each_sg(sg, s, nents, i)
> +		if (!arch_is_coherent())
> +			__dma_page_cpu_to_dev(sg_page(s), s->offset, s->length, dir);
> +}
> +
> +static dma_addr_t arm_iommu_map_page(struct device *dev, struct page *page,
> +	     unsigned long offset, size_t size, enum dma_data_direction dir,
> +	     struct dma_attrs *attrs)
> +{
> +	struct dma_iommu_mapping *mapping = dev->archdata.mapping;
> +	dma_addr_t dma_addr, iova;
> +	unsigned int phys;
> +	int ret, len = PAGE_ALIGN(size + offset);
> +
> +	if (!arch_is_coherent())
> +		__dma_page_cpu_to_dev(page, offset, size, dir);
> +
> +	dma_addr = iova = __alloc_iova(mapping, len);
> +	if (iova == ~0)
> +		goto fail;
> +
> +	dma_addr += offset;
> +	phys = page_to_phys(page);
> +	ret = iommu_map(mapping->domain, iova, phys, size, 0);
> +	if (ret < 0)
> +		goto fail;
> +
> +	return dma_addr;
> +fail:
> +	return ~0;
> +}
> +
> +static void arm_iommu_unmap_page(struct device *dev, dma_addr_t handle,
> +		size_t size, enum dma_data_direction dir,
> +		struct dma_attrs *attrs)
> +{
> +	struct dma_iommu_mapping *mapping = dev->archdata.mapping;
> +	dma_addr_t iova = handle & PAGE_MASK;
> +	struct page *page = phys_to_page(iommu_iova_to_phys(mapping->domain, iova));
> +	int offset = handle & ~PAGE_MASK;
> +
> +	if (!iova)
> +		return;
> +
> +	if (!arch_is_coherent())
> +		__dma_page_dev_to_cpu(page, offset, size, dir);
> +
> +	iommu_unmap(mapping->domain, iova, size);
> +	__free_iova(mapping, iova, size);
> +}
> +
> +static void arm_iommu_sync_single_for_cpu(struct device *dev,
> +		dma_addr_t handle, size_t size, enum dma_data_direction dir)
> +{
> +	struct dma_iommu_mapping *mapping = dev->archdata.mapping;
> +	dma_addr_t iova = handle & PAGE_MASK;
> +	struct page *page = phys_to_page(iommu_iova_to_phys(mapping->domain, iova));
> +	unsigned int offset = handle & ~PAGE_MASK;
> +
> +	if (!iova)
> +		return;
> +
> +	if (!arch_is_coherent())
> +		__dma_page_dev_to_cpu(page, offset, size, dir);
> +}
> +
> +static void arm_iommu_sync_single_for_device(struct device *dev,
> +		dma_addr_t handle, size_t size, enum dma_data_direction dir)
> +{
> +	struct dma_iommu_mapping *mapping = dev->archdata.mapping;
> +	dma_addr_t iova = handle & PAGE_MASK;
> +	struct page *page = phys_to_page(iommu_iova_to_phys(mapping->domain, iova));
> +	unsigned int offset = handle & ~PAGE_MASK;
> +
> +	if (!iova)
> +		return;
> +
> +	__dma_page_cpu_to_dev(page, offset, size, dir);
> +}
> +
> +struct dma_map_ops iommu_ops = {
> +	.alloc		= arm_iommu_alloc_attrs,
> +	.free		= arm_iommu_free_attrs,
> +	.mmap		= arm_iommu_mmap_attrs,
> +
> +	.map_page		= arm_iommu_map_page,
> +	.unmap_page		= arm_iommu_unmap_page,
> +	.sync_single_for_cpu	= arm_iommu_sync_single_for_cpu,
> +	.sync_single_for_device	= arm_iommu_sync_single_for_device,
> +
> +	.map_sg			= arm_iommu_map_sg,
> +	.unmap_sg		= arm_iommu_unmap_sg,
> +	.sync_sg_for_cpu	= arm_iommu_sync_sg_for_cpu,
> +	.sync_sg_for_device	= arm_iommu_sync_sg_for_device,
> +};
> +
> +struct dma_iommu_mapping *
> +arm_iommu_create_mapping(struct bus_type *bus, dma_addr_t base, size_t size,
> +			 int order)
> +{
> +	unsigned int count = (size >> PAGE_SHIFT) - order;
> +	unsigned int bitmap_size = BITS_TO_LONGS(count) * sizeof(long);
> +	struct dma_iommu_mapping *mapping;
> +	int err = -ENOMEM;
> +
> +	mapping = kzalloc(sizeof(struct dma_iommu_mapping), GFP_KERNEL);
> +	if (!mapping)
> +		goto err;
> +
> +	mapping->bitmap = kzalloc(bitmap_size, GFP_KERNEL);
> +	if (!mapping->bitmap)
> +		goto err2;
> +
> +	mapping->base = base;
> +	mapping->bits = bitmap_size;
> +	mapping->order = order;
> +	spin_lock_init(&mapping->lock);
> +
> +	mapping->domain = iommu_domain_alloc(bus);
> +	if (!mapping->domain)
> +		goto err3;
> +
> +	kref_init(&mapping->kref);
> +	return mapping;
> +err3:
> +	kfree(mapping->bitmap);
> +err2:
> +	kfree(mapping);
> +err:
> +	return ERR_PTR(err);
> +}
> +EXPORT_SYMBOL(arm_iommu_create_mapping);
> +
> +static void release_iommu_mapping(struct kref *kref)
> +{
> +	struct dma_iommu_mapping *mapping =
> +		container_of(kref, struct dma_iommu_mapping, kref);
> +
> +	iommu_domain_free(mapping->domain);
> +	kfree(mapping->bitmap);
> +	kfree(mapping);
> +}
> +
> +void arm_iommu_release_mapping(struct dma_iommu_mapping *mapping)
> +{
> +	if (mapping)
> +		kref_put(&mapping->kref, release_iommu_mapping);
> +}
> +EXPORT_SYMBOL(arm_iommu_release_mapping);
> +
> +int arm_iommu_attach_device(struct device *dev,
> +			    struct dma_iommu_mapping *mapping)
> +{
> +	int err;
> +
> +	err = iommu_attach_device(mapping->domain, dev);
> +	if (err)
> +		return err;
> +
> +	kref_get(&mapping->kref);
> +	dev->archdata.mapping = mapping;
> +	set_dma_ops(dev, &iommu_ops);
> +
> +	printk(KERN_INFO "Attached IOMMU controller to %s device.\n", dev_name(dev));

pr_debug?

> +	return 0;
> +}
> +EXPORT_SYMBOL(arm_iommu_attach_device);
> +
> +#endif
> diff --git a/arch/arm/mm/vmregion.h b/arch/arm/mm/vmregion.h
> index 15e9f04..6bbc402 100644
> --- a/arch/arm/mm/vmregion.h
> +++ b/arch/arm/mm/vmregion.h
> @@ -17,7 +17,7 @@ struct arm_vmregion {
>  	struct list_head	vm_list;
>  	unsigned long		vm_start;
>  	unsigned long		vm_end;
> -	struct page		*vm_pages;
> +	void			*priv;
>  	int			vm_active;
>  };

You might want to CC the ARM MM maintainers here to get their feedback.

Besides the comments I made, it looks good. You can stick Reviewed-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
if you would like on the patch.

>  
> -- 
> 1.7.1.569.g6f426
> 
> _______________________________________________
> iommu mailing list
> iommu@lists.linux-foundation.org
> https://lists.linuxfoundation.org/mailman/listinfo/iommu

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