Subject: [RFC/PATCH 2/9] arm: dma-mapping: Support IOMMU mappings spanning the full 32 bits range

From: [email-masked] (Robin Murphy)
Date: Tue, 19 May 2015 11:17:32 +0100

Hi Laurent,

On 15/05/15 00:00, Laurent Pinchart wrote:
> The arm_iommu_create_mapping() function takes the IOMMU mapping size as
> a size_t, limiting the size to 4GB - 1 on 32 bit platforms while most
> bus masters would support the full 32 bits range. Fix this by passing
> the size as a 64 bits integer, and limiting it to 4GB for now.

FYI there's already an almost-identical patch in -rc3 from Marek fixing 
this: 1424532b2163 ("ARM: 8347/1: dma-mapping: fix off-by-one check in 
arm_setup_iommu_dma_ops").

Robin.

>
> Signed-off-by: Laurent Pinchart <[email-masked]>
> ---
>   arch/arm/include/asm/dma-iommu.h |  2 +-
>   arch/arm/mm/dma-mapping.c        | 12 +++---------
>   2 files changed, 4 insertions(+), 10 deletions(-)
>
> diff --git a/arch/arm/include/asm/dma-iommu.h b/arch/arm/include/asm/dma-iommu.h
> index 8e3fcb924db6..2ef282f96651 100644
> --- a/arch/arm/include/asm/dma-iommu.h
> +++ b/arch/arm/include/asm/dma-iommu.h
> @@ -25,7 +25,7 @@ struct dma_iommu_mapping {
>   };
>
>   struct dma_iommu_mapping *
> -arm_iommu_create_mapping(struct bus_type *bus, dma_addr_t base, size_t size);
> +arm_iommu_create_mapping(struct bus_type *bus, dma_addr_t base, u64 size);
>
>   void arm_iommu_release_mapping(struct dma_iommu_mapping *mapping);
>
> diff --git a/arch/arm/mm/dma-mapping.c b/arch/arm/mm/dma-mapping.c
> index 7aa5e339a596..c69e216a0cf9 100644
> --- a/arch/arm/mm/dma-mapping.c
> +++ b/arch/arm/mm/dma-mapping.c
> @@ -1878,7 +1878,7 @@ struct dma_map_ops iommu_coherent_ops = {
>    * arm_iommu_attach_device function.
>    */
>   struct dma_iommu_mapping *
> -arm_iommu_create_mapping(struct bus_type *bus, dma_addr_t base, size_t size)
> +arm_iommu_create_mapping(struct bus_type *bus, dma_addr_t base, u64 size)
>   {
>   	unsigned int bits = size >> PAGE_SHIFT;
>   	unsigned int bitmap_size = BITS_TO_LONGS(bits) * sizeof(long);
> @@ -1886,7 +1886,8 @@ arm_iommu_create_mapping(struct bus_type *bus, dma_addr_t base, size_t size)
>   	int extensions = 1;
>   	int err = -ENOMEM;
>
> -	if (!bitmap_size)
> +	/* Limit the size to 4GB for now. */
> +	if (!size || size > (1ULL << 32))
>   		return ERR_PTR(-EINVAL);
>
>   	if (bitmap_size > PAGE_SIZE) {
> @@ -2057,13 +2058,6 @@ static bool arm_setup_iommu_dma_ops(struct device *dev, u64 dma_base, u64 size,
>   	if (!iommu)
>   		return false;
>
> -	/*
> -	 * currently arm_iommu_create_mapping() takes a max of size_t
> -	 * for size param. So check this limit for now.
> -	 */
> -	if (size > SIZE_MAX)
> -		return false;
> -
>   	mapping = arm_iommu_create_mapping(dev->bus, dma_base, size);
>   	if (IS_ERR(mapping)) {
>   		pr_warn("Failed to create %llu-byte IOMMU mapping for device %s\n",
>