linux-kernel - Re: [PATCH 04/19] dma-iommu: remove the flush

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Date:   Fri, 1 Feb 2019 15:28:24 +0000
From:   Robin Murphy <robin.murphy@....com>
To:     Christoph Hellwig <hch@....de>
Cc:     Joerg Roedel <joro@...tes.org>,
        Catalin Marinas <catalin.marinas@....com>,
        Will Deacon <will.deacon@....com>,
        Tom Lendacky <thomas.lendacky@....com>,
        iommu@...ts.linux-foundation.org,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 04/19] dma-iommu: remove the flush_page callback

On 14/01/2019 09:41, Christoph Hellwig wrote:
> We now have a arch_dma_prep_coherent architecture hook that is used
> for the generic DMA remap allocator, and we should use the same
> interface for the dma-iommu code.

Agreed - I'd definitely ack a version of this change which didn't depend 
on patch #3 ;)

Robin.

> Signed-off-by: Christoph Hellwig <hch@....de>
> ---
>   arch/arm64/mm/dma-mapping.c |  8 +-------
>   drivers/iommu/dma-iommu.c   | 14 ++++----------
>   include/linux/dma-iommu.h   |  3 +--
>   3 files changed, 6 insertions(+), 19 deletions(-)
> 
> diff --git a/arch/arm64/mm/dma-mapping.c b/arch/arm64/mm/dma-mapping.c
> index fb0908456a1f..75fe7273a1e4 100644
> --- a/arch/arm64/mm/dma-mapping.c
> +++ b/arch/arm64/mm/dma-mapping.c
> @@ -104,12 +104,6 @@ arch_initcall(arm64_dma_init);
>   #include <linux/platform_device.h>
>   #include <linux/amba/bus.h>
>   
> -/* Thankfully, all cache ops are by VA so we can ignore phys here */
> -static void flush_page(struct device *dev, const void *virt, phys_addr_t phys)
> -{
> -	__dma_flush_area(virt, PAGE_SIZE);
> -}
> -
>   static void *__iommu_alloc_attrs(struct device *dev, size_t size,
>   				 dma_addr_t *handle, gfp_t gfp,
>   				 unsigned long attrs)
> @@ -186,7 +180,7 @@ static void *__iommu_alloc_attrs(struct device *dev, size_t size,
>   		struct page **pages;
>   
>   		pages = iommu_dma_alloc(dev, iosize, gfp, attrs, ioprot,
> -					handle, flush_page);
> +					handle);
>   		if (!pages)
>   			return NULL;
>   
> diff --git a/drivers/iommu/dma-iommu.c b/drivers/iommu/dma-iommu.c
> index 4f5546a103d8..d6a437385b26 100644
> --- a/drivers/iommu/dma-iommu.c
> +++ b/drivers/iommu/dma-iommu.c
> @@ -22,6 +22,7 @@
>   #include <linux/acpi_iort.h>
>   #include <linux/device.h>
>   #include <linux/dma-iommu.h>
> +#include <linux/dma-noncoherent.h>
>   #include <linux/gfp.h>
>   #include <linux/huge_mm.h>
>   #include <linux/iommu.h>
> @@ -533,8 +534,6 @@ void iommu_dma_free(struct device *dev, struct page **pages, size_t size,
>    * @attrs: DMA attributes for this allocation
>    * @prot: IOMMU mapping flags
>    * @handle: Out argument for allocated DMA handle
> - * @flush_page: Arch callback which must ensure PAGE_SIZE bytes from the
> - *		given VA/PA are visible to the given non-coherent device.
>    *
>    * If @size is less than PAGE_SIZE, then a full CPU page will be allocated,
>    * but an IOMMU which supports smaller pages might not map the whole thing.
> @@ -543,8 +542,7 @@ void iommu_dma_free(struct device *dev, struct page **pages, size_t size,
>    *	   or NULL on failure.
>    */
>   struct page **iommu_dma_alloc(struct device *dev, size_t size, gfp_t gfp,
> -		unsigned long attrs, int prot, dma_addr_t *handle,
> -		void (*flush_page)(struct device *, const void *, phys_addr_t))
> +		unsigned long attrs, int prot, dma_addr_t *handle)
>   {
>   	struct iommu_domain *domain = iommu_get_dma_domain(dev);
>   	struct iommu_dma_cookie *cookie = domain->iova_cookie;
> @@ -580,12 +578,8 @@ struct page **iommu_dma_alloc(struct device *dev, size_t size, gfp_t gfp,
>   	for (i = 0; i < count; i++) {
>   		phys_addr_t phys = page_to_phys(pages[i]);
>   
> -		if (!(prot & IOMMU_CACHE)) {
> -			void *vaddr = kmap_atomic(pages[i]);
> -
> -			flush_page(dev, vaddr, phys);
> -			kunmap_atomic(vaddr);
> -		}
> +		if (!(prot & IOMMU_CACHE))
> +			arch_dma_prep_coherent(pages[i], PAGE_SIZE);
>   
>   		if (iommu_map(domain, iova + mapped, phys, PAGE_SIZE, prot))
>   			goto out_unmap;
> diff --git a/include/linux/dma-iommu.h b/include/linux/dma-iommu.h
> index 65aa888c2768..59e606f78626 100644
> --- a/include/linux/dma-iommu.h
> +++ b/include/linux/dma-iommu.h
> @@ -43,8 +43,7 @@ int dma_info_to_prot(enum dma_data_direction dir, bool coherent,
>    * the arch code to take care of attributes and cache maintenance
>    */
>   struct page **iommu_dma_alloc(struct device *dev, size_t size, gfp_t gfp,
> -		unsigned long attrs, int prot, dma_addr_t *handle,
> -		void (*flush_page)(struct device *, const void *, phys_addr_t));
> +		unsigned long attrs, int prot, dma_addr_t *handle);
>   void iommu_dma_free(struct device *dev, struct page **pages, size_t size,
>   		dma_addr_t *handle);
>   
>