linux-kernel - Re: [PATCH V7 5/8] arm64/dma-mapping: Implement DMA_ATTR

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Message-ID: <7d09fc5a-9425-c171-e469-2759534de2dc@arm.com>
Date:   Tue, 13 Dec 2016 14:02:33 +0000
From:   Robin Murphy <robin.murphy@....com>
To:     Sricharan R <sricharan@...eaurora.org>, jcrouse@...eaurora.org,
        pdaly@...eaurora.org, jgebben@...eaurora.org, joro@...tes.org,
        linux-kernel@...r.kernel.org, pratikp@...eaurora.org,
        iommu@...ts.linux-foundation.org, tzeng@...eaurora.org,
        linux-arm-kernel@...ts.infradead.org, will.deacon@....com,
        mitchelh@...eaurora.org, vinod.koul@...el.com
Cc:     dan.j.williams@...el.com
Subject: Re: [PATCH V7 5/8] arm64/dma-mapping: Implement DMA_ATTR_PRIVILEGED

On 12/12/16 18:38, Sricharan R wrote:
> From: Mitchel Humpherys <mitchelh@...eaurora.org>
> 
> The newly added DMA_ATTR_PRIVILEGED is useful for creating mappings that
> are only accessible to privileged DMA engines.  Implement it in
> dma-iommu.c so that the ARM64 DMA IOMMU mapper can make use of it.
> 
> Reviewed-by: Robin Murphy <robin.murphy@....com>
> Tested-by: Robin Murphy <robin.murphy@....com>
> Acked-by: Will Deacon <will.deacon@....com>
> Signed-off-by: Mitchel Humpherys <mitchelh@...eaurora.org>
> ---
>  arch/arm64/mm/dma-mapping.c |  6 +++---
>  drivers/iommu/dma-iommu.c   | 10 ++++++++--
>  include/linux/dma-iommu.h   |  3 ++-
>  3 files changed, 13 insertions(+), 6 deletions(-)
> 
> diff --git a/arch/arm64/mm/dma-mapping.c b/arch/arm64/mm/dma-mapping.c
> index 401f79a..ae76ead 100644
> --- a/arch/arm64/mm/dma-mapping.c
> +++ b/arch/arm64/mm/dma-mapping.c
> @@ -557,7 +557,7 @@ static void *__iommu_alloc_attrs(struct device *dev, size_t size,
>  				 unsigned long attrs)
>  {
>  	bool coherent = is_device_dma_coherent(dev);
> -	int ioprot = dma_direction_to_prot(DMA_BIDIRECTIONAL, coherent);
> +	int ioprot = dma_info_to_prot(DMA_BIDIRECTIONAL, coherent, attrs);
>  	size_t iosize = size;
>  	void *addr;
>  
> @@ -711,7 +711,7 @@ static dma_addr_t __iommu_map_page(struct device *dev, struct page *page,
>  				   unsigned long attrs)
>  {
>  	bool coherent = is_device_dma_coherent(dev);
> -	int prot = dma_direction_to_prot(dir, coherent);
> +	int prot = dma_info_to_prot(dir, coherent, attrs);
>  	dma_addr_t dev_addr = iommu_dma_map_page(dev, page, offset, size, prot);
>  
>  	if (!iommu_dma_mapping_error(dev, dev_addr) &&
> @@ -769,7 +769,7 @@ static int __iommu_map_sg_attrs(struct device *dev, struct scatterlist *sgl,
>  		__iommu_sync_sg_for_device(dev, sgl, nelems, dir);
>  
>  	return iommu_dma_map_sg(dev, sgl, nelems,
> -			dma_direction_to_prot(dir, coherent));
> +				dma_info_to_prot(dir, coherent, attrs));
>  }
>  
>  static void __iommu_unmap_sg_attrs(struct device *dev,
> diff --git a/drivers/iommu/dma-iommu.c b/drivers/iommu/dma-iommu.c
> index d2a7a46..756d5e0 100644
> --- a/drivers/iommu/dma-iommu.c
> +++ b/drivers/iommu/dma-iommu.c
> @@ -182,16 +182,22 @@ int iommu_dma_init_domain(struct iommu_domain *domain, dma_addr_t base,
>  EXPORT_SYMBOL(iommu_dma_init_domain);
>  
>  /**
> - * dma_direction_to_prot - Translate DMA API directions to IOMMU API page flags
> + * dma_info_to_prot - Translate DMA API directions and attributes to IOMMU API
> + *                    page flags.
>   * @dir: Direction of DMA transfer
>   * @coherent: Is the DMA master cache-coherent?
> + * @attrs: DMA attributes for the mapping
>   *
>   * Return: corresponding IOMMU API page protection flags
>   */
> -int dma_direction_to_prot(enum dma_data_direction dir, bool coherent)
> +int dma_info_to_prot(enum dma_data_direction dir, bool coherent,
> +		     unsigned long attrs)
>  {
>  	int prot = coherent ? IOMMU_CACHE : 0;
>  
> +	if (attrs & DMA_ATTR_PRIVILEGED)
> +		prot |= IOMMU_PRIV;
> +
>  	switch (dir) {
>  	case DMA_BIDIRECTIONAL:
>  		return prot | IOMMU_READ | IOMMU_WRITE;

...and applying against -next now also needs this hunk:

@@ -639,7 +639,7 @@ dma_addr_t iommu_dma_map_resource(struct device
*dev, phys_addr_t phys,
 		size_t size, enum dma_data_direction dir, unsigned long attrs)
 {
 	return __iommu_dma_map(dev, phys, size,
-			dma_direction_to_prot(dir, false) | IOMMU_MMIO);
+			dma_info_to_prot(dir, false, attrs) | IOMMU_MMIO);
 }

 void iommu_dma_unmap_resource(struct device *dev, dma_addr_t handle,

With those two issues fixed up, I've given the series (applied to
next-20161213) a spin on a SMMUv3/PL330 fast model and it still checks out.

Robin.

> diff --git a/include/linux/dma-iommu.h b/include/linux/dma-iommu.h
> index 32c5890..a203181 100644
> --- a/include/linux/dma-iommu.h
> +++ b/include/linux/dma-iommu.h
> @@ -34,7 +34,8 @@ int iommu_dma_init_domain(struct iommu_domain *domain, dma_addr_t base,
>  		u64 size, struct device *dev);
>  
>  /* General helpers for DMA-API <-> IOMMU-API interaction */
> -int dma_direction_to_prot(enum dma_data_direction dir, bool coherent);
> +int dma_info_to_prot(enum dma_data_direction dir, bool coherent,
> +		     unsigned long attrs);
>  
>  /*
>   * These implement the bulk of the relevant DMA mapping callbacks, but require
>