a few xen swiotlb cleanups

a few xen swiotlb cleanups

[Christoph Hellwig]

Hi all,

below are a couple of cleanups for swiotlb-xen.c.  They were done in
preparation of eventually using the dma-noncoherent.h cache flushing
hooks, but that final goal will need some major work to the arm32 code
first.  Until then I think these patches might be better in mainline
than in my local tree so that they don't bitrot.

a few xen swiotlb cleanups

[Christoph Hellwig]

Hi all,

below are a couple of cleanups for swiotlb-xen.c.  They were done in
preparation of eventually using the dma-noncoherent.h cache flushing
hooks, but that final goal will need some major work to the arm32 code
first.  Until then I think these patches might be better in mainline
than in my local tree so that they don't bitrot.
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[PATCH 1/4] swiotlb-xen: make instances match their method names

[Christoph Hellwig]

Just drop two pointless _attrs prefixes to make the code a little
more grep-able.

Signed-off-by: Christoph Hellwig <hch-jcswGhMUV9g@public.gmane.org>
---
 drivers/xen/swiotlb-xen.c | 17 +++++++----------
 1 file changed, 7 insertions(+), 10 deletions(-)

diff --git a/drivers/xen/swiotlb-xen.c b/drivers/xen/swiotlb-xen.c
index 877baf2a94f4..d4bc3aabd44d 100644
--- a/drivers/xen/swiotlb-xen.c
+++ b/drivers/xen/swiotlb-xen.c
@@ -504,9 +504,8 @@ xen_swiotlb_sync_single_for_device(struct device *hwdev, dma_addr_t dev_addr,
  * concerning calls here are the same as for swiotlb_unmap_page() above.
  */
 static void
-xen_swiotlb_unmap_sg_attrs(struct device *hwdev, struct scatterlist *sgl,
-			   int nelems, enum dma_data_direction dir,
-			   unsigned long attrs)
+xen_swiotlb_unmap_sg(struct device *hwdev, struct scatterlist *sgl, int nelems,
+		enum dma_data_direction dir, unsigned long attrs)
 {
 	struct scatterlist *sg;
 	int i;
@@ -535,9 +534,8 @@ xen_swiotlb_unmap_sg_attrs(struct device *hwdev, struct scatterlist *sgl,
  * same here.
  */
 static int
-xen_swiotlb_map_sg_attrs(struct device *hwdev, struct scatterlist *sgl,
-			 int nelems, enum dma_data_direction dir,
-			 unsigned long attrs)
+xen_swiotlb_map_sg(struct device *hwdev, struct scatterlist *sgl, int nelems,
+		enum dma_data_direction dir, unsigned long attrs)
 {
 	struct scatterlist *sg;
 	int i;
@@ -562,8 +560,7 @@ xen_swiotlb_map_sg_attrs(struct device *hwdev, struct scatterlist *sgl,
 				/* Don't panic here, we expect map_sg users
 				   to do proper error handling. */
 				attrs |= DMA_ATTR_SKIP_CPU_SYNC;
-				xen_swiotlb_unmap_sg_attrs(hwdev, sgl, i, dir,
-							   attrs);
+				xen_swiotlb_unmap_sg(hwdev, sgl, i, dir, attrs);
 				sg_dma_len(sgl) = 0;
 				return 0;
 			}
@@ -690,8 +687,8 @@ const struct dma_map_ops xen_swiotlb_dma_ops = {
 	.sync_single_for_device = xen_swiotlb_sync_single_for_device,
 	.sync_sg_for_cpu = xen_swiotlb_sync_sg_for_cpu,
 	.sync_sg_for_device = xen_swiotlb_sync_sg_for_device,
-	.map_sg = xen_swiotlb_map_sg_attrs,
-	.unmap_sg = xen_swiotlb_unmap_sg_attrs,
+	.map_sg = xen_swiotlb_map_sg,
+	.unmap_sg = xen_swiotlb_unmap_sg,
 	.map_page = xen_swiotlb_map_page,
 	.unmap_page = xen_swiotlb_unmap_page,
 	.dma_supported = xen_swiotlb_dma_supported,
-- 
2.20.1

[PATCH 1/4] swiotlb-xen: make instances match their method names

[Christoph Hellwig]

Just drop two pointless _attrs prefixes to make the code a little
more grep-able.

Signed-off-by: Christoph Hellwig <hch@lst.de>
---
 drivers/xen/swiotlb-xen.c | 17 +++++++----------
 1 file changed, 7 insertions(+), 10 deletions(-)

diff --git a/drivers/xen/swiotlb-xen.c b/drivers/xen/swiotlb-xen.c
index 877baf2a94f4..d4bc3aabd44d 100644
--- a/drivers/xen/swiotlb-xen.c
+++ b/drivers/xen/swiotlb-xen.c
@@ -504,9 +504,8 @@ xen_swiotlb_sync_single_for_device(struct device *hwdev, dma_addr_t dev_addr,
  * concerning calls here are the same as for swiotlb_unmap_page() above.
  */
 static void
-xen_swiotlb_unmap_sg_attrs(struct device *hwdev, struct scatterlist *sgl,
-			   int nelems, enum dma_data_direction dir,
-			   unsigned long attrs)
+xen_swiotlb_unmap_sg(struct device *hwdev, struct scatterlist *sgl, int nelems,
+		enum dma_data_direction dir, unsigned long attrs)
 {
 	struct scatterlist *sg;
 	int i;
@@ -535,9 +534,8 @@ xen_swiotlb_unmap_sg_attrs(struct device *hwdev, struct scatterlist *sgl,
  * same here.
  */
 static int
-xen_swiotlb_map_sg_attrs(struct device *hwdev, struct scatterlist *sgl,
-			 int nelems, enum dma_data_direction dir,
-			 unsigned long attrs)
+xen_swiotlb_map_sg(struct device *hwdev, struct scatterlist *sgl, int nelems,
+		enum dma_data_direction dir, unsigned long attrs)
 {
 	struct scatterlist *sg;
 	int i;
@@ -562,8 +560,7 @@ xen_swiotlb_map_sg_attrs(struct device *hwdev, struct scatterlist *sgl,
 				/* Don't panic here, we expect map_sg users
 				   to do proper error handling. */
 				attrs |= DMA_ATTR_SKIP_CPU_SYNC;
-				xen_swiotlb_unmap_sg_attrs(hwdev, sgl, i, dir,
-							   attrs);
+				xen_swiotlb_unmap_sg(hwdev, sgl, i, dir, attrs);
 				sg_dma_len(sgl) = 0;
 				return 0;
 			}
@@ -690,8 +687,8 @@ const struct dma_map_ops xen_swiotlb_dma_ops = {
 	.sync_single_for_device = xen_swiotlb_sync_single_for_device,
 	.sync_sg_for_cpu = xen_swiotlb_sync_sg_for_cpu,
 	.sync_sg_for_device = xen_swiotlb_sync_sg_for_device,
-	.map_sg = xen_swiotlb_map_sg_attrs,
-	.unmap_sg = xen_swiotlb_unmap_sg_attrs,
+	.map_sg = xen_swiotlb_map_sg,
+	.unmap_sg = xen_swiotlb_unmap_sg,
 	.map_page = xen_swiotlb_map_page,
 	.unmap_page = xen_swiotlb_unmap_page,
 	.dma_supported = xen_swiotlb_dma_supported,
-- 
2.20.1

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Re: [PATCH 1/4] swiotlb-xen: make instances match their method names

[Stefano Stabellini]

On Thu, 11 Apr 2019, Christoph Hellwig wrote:
> Just drop two pointless _attrs prefixes to make the code a little
> more grep-able.
> 
> Signed-off-by: Christoph Hellwig <hch-jcswGhMUV9g@public.gmane.org>

Reviewed-by: Stefano Stabellini <sstabellini-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org>

> ---
>  drivers/xen/swiotlb-xen.c | 17 +++++++----------
>  1 file changed, 7 insertions(+), 10 deletions(-)
> 
> diff --git a/drivers/xen/swiotlb-xen.c b/drivers/xen/swiotlb-xen.c
> index 877baf2a94f4..d4bc3aabd44d 100644
> --- a/drivers/xen/swiotlb-xen.c
> +++ b/drivers/xen/swiotlb-xen.c
> @@ -504,9 +504,8 @@ xen_swiotlb_sync_single_for_device(struct device *hwdev, dma_addr_t dev_addr,
>   * concerning calls here are the same as for swiotlb_unmap_page() above.
>   */
>  static void
> -xen_swiotlb_unmap_sg_attrs(struct device *hwdev, struct scatterlist *sgl,
> -			   int nelems, enum dma_data_direction dir,
> -			   unsigned long attrs)
> +xen_swiotlb_unmap_sg(struct device *hwdev, struct scatterlist *sgl, int nelems,
> +		enum dma_data_direction dir, unsigned long attrs)
>  {
>  	struct scatterlist *sg;
>  	int i;
> @@ -535,9 +534,8 @@ xen_swiotlb_unmap_sg_attrs(struct device *hwdev, struct scatterlist *sgl,
>   * same here.
>   */
>  static int
> -xen_swiotlb_map_sg_attrs(struct device *hwdev, struct scatterlist *sgl,
> -			 int nelems, enum dma_data_direction dir,
> -			 unsigned long attrs)
> +xen_swiotlb_map_sg(struct device *hwdev, struct scatterlist *sgl, int nelems,
> +		enum dma_data_direction dir, unsigned long attrs)
>  {
>  	struct scatterlist *sg;
>  	int i;
> @@ -562,8 +560,7 @@ xen_swiotlb_map_sg_attrs(struct device *hwdev, struct scatterlist *sgl,
>  				/* Don't panic here, we expect map_sg users
>  				   to do proper error handling. */
>  				attrs |= DMA_ATTR_SKIP_CPU_SYNC;
> -				xen_swiotlb_unmap_sg_attrs(hwdev, sgl, i, dir,
> -							   attrs);
> +				xen_swiotlb_unmap_sg(hwdev, sgl, i, dir, attrs);
>  				sg_dma_len(sgl) = 0;
>  				return 0;
>  			}
> @@ -690,8 +687,8 @@ const struct dma_map_ops xen_swiotlb_dma_ops = {
>  	.sync_single_for_device = xen_swiotlb_sync_single_for_device,
>  	.sync_sg_for_cpu = xen_swiotlb_sync_sg_for_cpu,
>  	.sync_sg_for_device = xen_swiotlb_sync_sg_for_device,
> -	.map_sg = xen_swiotlb_map_sg_attrs,
> -	.unmap_sg = xen_swiotlb_unmap_sg_attrs,
> +	.map_sg = xen_swiotlb_map_sg,
> +	.unmap_sg = xen_swiotlb_unmap_sg,
>  	.map_page = xen_swiotlb_map_page,
>  	.unmap_page = xen_swiotlb_unmap_page,
>  	.dma_supported = xen_swiotlb_dma_supported,
> -- 
> 2.20.1
> 

Re: [PATCH 1/4] swiotlb-xen: make instances match their method names

[Stefano Stabellini]

On Thu, 11 Apr 2019, Christoph Hellwig wrote:
> Just drop two pointless _attrs prefixes to make the code a little
> more grep-able.
> 
> Signed-off-by: Christoph Hellwig <hch@lst.de>

Reviewed-by: Stefano Stabellini <sstabellini@kernel.org>

> ---
>  drivers/xen/swiotlb-xen.c | 17 +++++++----------
>  1 file changed, 7 insertions(+), 10 deletions(-)
> 
> diff --git a/drivers/xen/swiotlb-xen.c b/drivers/xen/swiotlb-xen.c
> index 877baf2a94f4..d4bc3aabd44d 100644
> --- a/drivers/xen/swiotlb-xen.c
> +++ b/drivers/xen/swiotlb-xen.c
> @@ -504,9 +504,8 @@ xen_swiotlb_sync_single_for_device(struct device *hwdev, dma_addr_t dev_addr,
>   * concerning calls here are the same as for swiotlb_unmap_page() above.
>   */
>  static void
> -xen_swiotlb_unmap_sg_attrs(struct device *hwdev, struct scatterlist *sgl,
> -			   int nelems, enum dma_data_direction dir,
> -			   unsigned long attrs)
> +xen_swiotlb_unmap_sg(struct device *hwdev, struct scatterlist *sgl, int nelems,
> +		enum dma_data_direction dir, unsigned long attrs)
>  {
>  	struct scatterlist *sg;
>  	int i;
> @@ -535,9 +534,8 @@ xen_swiotlb_unmap_sg_attrs(struct device *hwdev, struct scatterlist *sgl,
>   * same here.
>   */
>  static int
> -xen_swiotlb_map_sg_attrs(struct device *hwdev, struct scatterlist *sgl,
> -			 int nelems, enum dma_data_direction dir,
> -			 unsigned long attrs)
> +xen_swiotlb_map_sg(struct device *hwdev, struct scatterlist *sgl, int nelems,
> +		enum dma_data_direction dir, unsigned long attrs)
>  {
>  	struct scatterlist *sg;
>  	int i;
> @@ -562,8 +560,7 @@ xen_swiotlb_map_sg_attrs(struct device *hwdev, struct scatterlist *sgl,
>  				/* Don't panic here, we expect map_sg users
>  				   to do proper error handling. */
>  				attrs |= DMA_ATTR_SKIP_CPU_SYNC;
> -				xen_swiotlb_unmap_sg_attrs(hwdev, sgl, i, dir,
> -							   attrs);
> +				xen_swiotlb_unmap_sg(hwdev, sgl, i, dir, attrs);
>  				sg_dma_len(sgl) = 0;
>  				return 0;
>  			}
> @@ -690,8 +687,8 @@ const struct dma_map_ops xen_swiotlb_dma_ops = {
>  	.sync_single_for_device = xen_swiotlb_sync_single_for_device,
>  	.sync_sg_for_cpu = xen_swiotlb_sync_sg_for_cpu,
>  	.sync_sg_for_device = xen_swiotlb_sync_sg_for_device,
> -	.map_sg = xen_swiotlb_map_sg_attrs,
> -	.unmap_sg = xen_swiotlb_unmap_sg_attrs,
> +	.map_sg = xen_swiotlb_map_sg,
> +	.unmap_sg = xen_swiotlb_unmap_sg,
>  	.map_page = xen_swiotlb_map_page,
>  	.unmap_page = xen_swiotlb_unmap_page,
>  	.dma_supported = xen_swiotlb_dma_supported,
> -- 
> 2.20.1
> 
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[PATCH 2/4] swiotlb-xen: use ->map_page to implement ->map_sg

[Christoph Hellwig]

We can simply loop over the segments and map them, removing lots of
duplicate code.

Signed-off-by: Christoph Hellwig <hch-jcswGhMUV9g@public.gmane.org>
---
 drivers/xen/swiotlb-xen.c | 68 ++++++---------------------------------
 1 file changed, 10 insertions(+), 58 deletions(-)

diff --git a/drivers/xen/swiotlb-xen.c b/drivers/xen/swiotlb-xen.c
index d4bc3aabd44d..97a55c225593 100644
--- a/drivers/xen/swiotlb-xen.c
+++ b/drivers/xen/swiotlb-xen.c
@@ -517,24 +517,8 @@ xen_swiotlb_unmap_sg(struct device *hwdev, struct scatterlist *sgl, int nelems,
 
 }
 
-/*
- * Map a set of buffers described by scatterlist in streaming mode for DMA.
- * This is the scatter-gather version of the above xen_swiotlb_map_page
- * interface.  Here the scatter gather list elements are each tagged with the
- * appropriate dma address and length.  They are obtained via
- * sg_dma_{address,length}(SG).
- *
- * NOTE: An implementation may be able to use a smaller number of
- *       DMA address/length pairs than there are SG table elements.
- *       (for example via virtual mapping capabilities)
- *       The routine returns the number of addr/length pairs actually
- *       used, at most nents.
- *
- * Device ownership issues as mentioned above for xen_swiotlb_map_page are the
- * same here.
- */
 static int
-xen_swiotlb_map_sg(struct device *hwdev, struct scatterlist *sgl, int nelems,
+xen_swiotlb_map_sg(struct device *dev, struct scatterlist *sgl, int nelems,
 		enum dma_data_direction dir, unsigned long attrs)
 {
 	struct scatterlist *sg;
@@ -543,50 +527,18 @@ xen_swiotlb_map_sg(struct device *hwdev, struct scatterlist *sgl, int nelems,
 	BUG_ON(dir == DMA_NONE);
 
 	for_each_sg(sgl, sg, nelems, i) {
-		phys_addr_t paddr = sg_phys(sg);
-		dma_addr_t dev_addr = xen_phys_to_bus(paddr);
-
-		if (swiotlb_force == SWIOTLB_FORCE ||
-		    xen_arch_need_swiotlb(hwdev, paddr, dev_addr) ||
-		    !dma_capable(hwdev, dev_addr, sg->length) ||
-		    range_straddles_page_boundary(paddr, sg->length)) {
-			phys_addr_t map = swiotlb_tbl_map_single(hwdev,
-								 start_dma_addr,
-								 sg_phys(sg),
-								 sg->length,
-								 dir, attrs);
-			if (map == DMA_MAPPING_ERROR) {
-				dev_warn(hwdev, "swiotlb buffer is full\n");
-				/* Don't panic here, we expect map_sg users
-				   to do proper error handling. */
-				attrs |= DMA_ATTR_SKIP_CPU_SYNC;
-				xen_swiotlb_unmap_sg(hwdev, sgl, i, dir, attrs);
-				sg_dma_len(sgl) = 0;
-				return 0;
-			}
-			dev_addr = xen_phys_to_bus(map);
-			xen_dma_map_page(hwdev, pfn_to_page(map >> PAGE_SHIFT),
-						dev_addr,
-						map & ~PAGE_MASK,
-						sg->length,
-						dir,
-						attrs);
-			sg->dma_address = dev_addr;
-		} else {
-			/* we are not interested in the dma_addr returned by
-			 * xen_dma_map_page, only in the potential cache flushes executed
-			 * by the function. */
-			xen_dma_map_page(hwdev, pfn_to_page(paddr >> PAGE_SHIFT),
-						dev_addr,
-						paddr & ~PAGE_MASK,
-						sg->length,
-						dir,
-						attrs);
-			sg->dma_address = dev_addr;
-		}
+		sg->dma_address = xen_swiotlb_map_page(dev, sg_page(sg),
+				sg->offset, sg->length, dir, attrs);
+		if (sg->dma_address == DMA_MAPPING_ERROR)
+			goto out_unmap;
 		sg_dma_len(sg) = sg->length;
 	}
+
 	return nelems;
+out_unmap:
+	xen_swiotlb_unmap_sg(dev, sgl, i, dir, attrs | DMA_ATTR_SKIP_CPU_SYNC);
+	sg_dma_len(sgl) = 0;
+	return 0;
 }
 
 /*
-- 
2.20.1

[PATCH 2/4] swiotlb-xen: use ->map_page to implement ->map_sg

[Christoph Hellwig]

We can simply loop over the segments and map them, removing lots of
duplicate code.

Signed-off-by: Christoph Hellwig <hch@lst.de>
---
 drivers/xen/swiotlb-xen.c | 68 ++++++---------------------------------
 1 file changed, 10 insertions(+), 58 deletions(-)

diff --git a/drivers/xen/swiotlb-xen.c b/drivers/xen/swiotlb-xen.c
index d4bc3aabd44d..97a55c225593 100644
--- a/drivers/xen/swiotlb-xen.c
+++ b/drivers/xen/swiotlb-xen.c
@@ -517,24 +517,8 @@ xen_swiotlb_unmap_sg(struct device *hwdev, struct scatterlist *sgl, int nelems,
 
 }
 
-/*
- * Map a set of buffers described by scatterlist in streaming mode for DMA.
- * This is the scatter-gather version of the above xen_swiotlb_map_page
- * interface.  Here the scatter gather list elements are each tagged with the
- * appropriate dma address and length.  They are obtained via
- * sg_dma_{address,length}(SG).
- *
- * NOTE: An implementation may be able to use a smaller number of
- *       DMA address/length pairs than there are SG table elements.
- *       (for example via virtual mapping capabilities)
- *       The routine returns the number of addr/length pairs actually
- *       used, at most nents.
- *
- * Device ownership issues as mentioned above for xen_swiotlb_map_page are the
- * same here.
- */
 static int
-xen_swiotlb_map_sg(struct device *hwdev, struct scatterlist *sgl, int nelems,
+xen_swiotlb_map_sg(struct device *dev, struct scatterlist *sgl, int nelems,
 		enum dma_data_direction dir, unsigned long attrs)
 {
 	struct scatterlist *sg;
@@ -543,50 +527,18 @@ xen_swiotlb_map_sg(struct device *hwdev, struct scatterlist *sgl, int nelems,
 	BUG_ON(dir == DMA_NONE);
 
 	for_each_sg(sgl, sg, nelems, i) {
-		phys_addr_t paddr = sg_phys(sg);
-		dma_addr_t dev_addr = xen_phys_to_bus(paddr);
-
-		if (swiotlb_force == SWIOTLB_FORCE ||
-		    xen_arch_need_swiotlb(hwdev, paddr, dev_addr) ||
-		    !dma_capable(hwdev, dev_addr, sg->length) ||
-		    range_straddles_page_boundary(paddr, sg->length)) {
-			phys_addr_t map = swiotlb_tbl_map_single(hwdev,
-								 start_dma_addr,
-								 sg_phys(sg),
-								 sg->length,
-								 dir, attrs);
-			if (map == DMA_MAPPING_ERROR) {
-				dev_warn(hwdev, "swiotlb buffer is full\n");
-				/* Don't panic here, we expect map_sg users
-				   to do proper error handling. */
-				attrs |= DMA_ATTR_SKIP_CPU_SYNC;
-				xen_swiotlb_unmap_sg(hwdev, sgl, i, dir, attrs);
-				sg_dma_len(sgl) = 0;
-				return 0;
-			}
-			dev_addr = xen_phys_to_bus(map);
-			xen_dma_map_page(hwdev, pfn_to_page(map >> PAGE_SHIFT),
-						dev_addr,
-						map & ~PAGE_MASK,
-						sg->length,
-						dir,
-						attrs);
-			sg->dma_address = dev_addr;
-		} else {
-			/* we are not interested in the dma_addr returned by
-			 * xen_dma_map_page, only in the potential cache flushes executed
-			 * by the function. */
-			xen_dma_map_page(hwdev, pfn_to_page(paddr >> PAGE_SHIFT),
-						dev_addr,
-						paddr & ~PAGE_MASK,
-						sg->length,
-						dir,
-						attrs);
-			sg->dma_address = dev_addr;
-		}
+		sg->dma_address = xen_swiotlb_map_page(dev, sg_page(sg),
+				sg->offset, sg->length, dir, attrs);
+		if (sg->dma_address == DMA_MAPPING_ERROR)
+			goto out_unmap;
 		sg_dma_len(sg) = sg->length;
 	}
+
 	return nelems;
+out_unmap:
+	xen_swiotlb_unmap_sg(dev, sgl, i, dir, attrs | DMA_ATTR_SKIP_CPU_SYNC);
+	sg_dma_len(sgl) = 0;
+	return 0;
 }
 
 /*
-- 
2.20.1

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Re: [PATCH 2/4] swiotlb-xen: use ->map_page to implement ->map_sg

[Stefano Stabellini]

On Thu, 11 Apr 2019, Christoph Hellwig wrote:
> We can simply loop over the segments and map them, removing lots of
> duplicate code.

Right, the only difference is the additional dma_capable check which is
good to have.

Reviewed-by: Stefano Stabellini <sstabellini-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org>


> Signed-off-by: Christoph Hellwig <hch-jcswGhMUV9g@public.gmane.org>
> ---
>  drivers/xen/swiotlb-xen.c | 68 ++++++---------------------------------
>  1 file changed, 10 insertions(+), 58 deletions(-)
> 
> diff --git a/drivers/xen/swiotlb-xen.c b/drivers/xen/swiotlb-xen.c
> index d4bc3aabd44d..97a55c225593 100644
> --- a/drivers/xen/swiotlb-xen.c
> +++ b/drivers/xen/swiotlb-xen.c
> @@ -517,24 +517,8 @@ xen_swiotlb_unmap_sg(struct device *hwdev, struct scatterlist *sgl, int nelems,
>  
>  }
>  
> -/*
> - * Map a set of buffers described by scatterlist in streaming mode for DMA.
> - * This is the scatter-gather version of the above xen_swiotlb_map_page
> - * interface.  Here the scatter gather list elements are each tagged with the
> - * appropriate dma address and length.  They are obtained via
> - * sg_dma_{address,length}(SG).
> - *
> - * NOTE: An implementation may be able to use a smaller number of
> - *       DMA address/length pairs than there are SG table elements.
> - *       (for example via virtual mapping capabilities)
> - *       The routine returns the number of addr/length pairs actually
> - *       used, at most nents.
> - *
> - * Device ownership issues as mentioned above for xen_swiotlb_map_page are the
> - * same here.
> - */
>  static int
> -xen_swiotlb_map_sg(struct device *hwdev, struct scatterlist *sgl, int nelems,
> +xen_swiotlb_map_sg(struct device *dev, struct scatterlist *sgl, int nelems,
>  		enum dma_data_direction dir, unsigned long attrs)
>  {
>  	struct scatterlist *sg;
> @@ -543,50 +527,18 @@ xen_swiotlb_map_sg(struct device *hwdev, struct scatterlist *sgl, int nelems,
>  	BUG_ON(dir == DMA_NONE);
>  
>  	for_each_sg(sgl, sg, nelems, i) {
> -		phys_addr_t paddr = sg_phys(sg);
> -		dma_addr_t dev_addr = xen_phys_to_bus(paddr);
> -
> -		if (swiotlb_force == SWIOTLB_FORCE ||
> -		    xen_arch_need_swiotlb(hwdev, paddr, dev_addr) ||
> -		    !dma_capable(hwdev, dev_addr, sg->length) ||
> -		    range_straddles_page_boundary(paddr, sg->length)) {
> -			phys_addr_t map = swiotlb_tbl_map_single(hwdev,
> -								 start_dma_addr,
> -								 sg_phys(sg),
> -								 sg->length,
> -								 dir, attrs);
> -			if (map == DMA_MAPPING_ERROR) {
> -				dev_warn(hwdev, "swiotlb buffer is full\n");
> -				/* Don't panic here, we expect map_sg users
> -				   to do proper error handling. */
> -				attrs |= DMA_ATTR_SKIP_CPU_SYNC;
> -				xen_swiotlb_unmap_sg(hwdev, sgl, i, dir, attrs);
> -				sg_dma_len(sgl) = 0;
> -				return 0;
> -			}
> -			dev_addr = xen_phys_to_bus(map);
> -			xen_dma_map_page(hwdev, pfn_to_page(map >> PAGE_SHIFT),
> -						dev_addr,
> -						map & ~PAGE_MASK,
> -						sg->length,
> -						dir,
> -						attrs);
> -			sg->dma_address = dev_addr;
> -		} else {
> -			/* we are not interested in the dma_addr returned by
> -			 * xen_dma_map_page, only in the potential cache flushes executed
> -			 * by the function. */
> -			xen_dma_map_page(hwdev, pfn_to_page(paddr >> PAGE_SHIFT),
> -						dev_addr,
> -						paddr & ~PAGE_MASK,
> -						sg->length,
> -						dir,
> -						attrs);
> -			sg->dma_address = dev_addr;
> -		}
> +		sg->dma_address = xen_swiotlb_map_page(dev, sg_page(sg),
> +				sg->offset, sg->length, dir, attrs);
> +		if (sg->dma_address == DMA_MAPPING_ERROR)
> +			goto out_unmap;
>  		sg_dma_len(sg) = sg->length;
>  	}
> +
>  	return nelems;
> +out_unmap:
> +	xen_swiotlb_unmap_sg(dev, sgl, i, dir, attrs | DMA_ATTR_SKIP_CPU_SYNC);
> +	sg_dma_len(sgl) = 0;
> +	return 0;
>  }
>  
>  /*
> -- 
> 2.20.1
> 

Re: [PATCH 2/4] swiotlb-xen: use ->map_page to implement ->map_sg

[Stefano Stabellini]

On Thu, 11 Apr 2019, Christoph Hellwig wrote:
> We can simply loop over the segments and map them, removing lots of
> duplicate code.

Right, the only difference is the additional dma_capable check which is
good to have.

Reviewed-by: Stefano Stabellini <sstabellini@kernel.org>


> Signed-off-by: Christoph Hellwig <hch@lst.de>
> ---
>  drivers/xen/swiotlb-xen.c | 68 ++++++---------------------------------
>  1 file changed, 10 insertions(+), 58 deletions(-)
> 
> diff --git a/drivers/xen/swiotlb-xen.c b/drivers/xen/swiotlb-xen.c
> index d4bc3aabd44d..97a55c225593 100644
> --- a/drivers/xen/swiotlb-xen.c
> +++ b/drivers/xen/swiotlb-xen.c
> @@ -517,24 +517,8 @@ xen_swiotlb_unmap_sg(struct device *hwdev, struct scatterlist *sgl, int nelems,
>  
>  }
>  
> -/*
> - * Map a set of buffers described by scatterlist in streaming mode for DMA.
> - * This is the scatter-gather version of the above xen_swiotlb_map_page
> - * interface.  Here the scatter gather list elements are each tagged with the
> - * appropriate dma address and length.  They are obtained via
> - * sg_dma_{address,length}(SG).
> - *
> - * NOTE: An implementation may be able to use a smaller number of
> - *       DMA address/length pairs than there are SG table elements.
> - *       (for example via virtual mapping capabilities)
> - *       The routine returns the number of addr/length pairs actually
> - *       used, at most nents.
> - *
> - * Device ownership issues as mentioned above for xen_swiotlb_map_page are the
> - * same here.
> - */
>  static int
> -xen_swiotlb_map_sg(struct device *hwdev, struct scatterlist *sgl, int nelems,
> +xen_swiotlb_map_sg(struct device *dev, struct scatterlist *sgl, int nelems,
>  		enum dma_data_direction dir, unsigned long attrs)
>  {
>  	struct scatterlist *sg;
> @@ -543,50 +527,18 @@ xen_swiotlb_map_sg(struct device *hwdev, struct scatterlist *sgl, int nelems,
>  	BUG_ON(dir == DMA_NONE);
>  
>  	for_each_sg(sgl, sg, nelems, i) {
> -		phys_addr_t paddr = sg_phys(sg);
> -		dma_addr_t dev_addr = xen_phys_to_bus(paddr);
> -
> -		if (swiotlb_force == SWIOTLB_FORCE ||
> -		    xen_arch_need_swiotlb(hwdev, paddr, dev_addr) ||
> -		    !dma_capable(hwdev, dev_addr, sg->length) ||
> -		    range_straddles_page_boundary(paddr, sg->length)) {
> -			phys_addr_t map = swiotlb_tbl_map_single(hwdev,
> -								 start_dma_addr,
> -								 sg_phys(sg),
> -								 sg->length,
> -								 dir, attrs);
> -			if (map == DMA_MAPPING_ERROR) {
> -				dev_warn(hwdev, "swiotlb buffer is full\n");
> -				/* Don't panic here, we expect map_sg users
> -				   to do proper error handling. */
> -				attrs |= DMA_ATTR_SKIP_CPU_SYNC;
> -				xen_swiotlb_unmap_sg(hwdev, sgl, i, dir, attrs);
> -				sg_dma_len(sgl) = 0;
> -				return 0;
> -			}
> -			dev_addr = xen_phys_to_bus(map);
> -			xen_dma_map_page(hwdev, pfn_to_page(map >> PAGE_SHIFT),
> -						dev_addr,
> -						map & ~PAGE_MASK,
> -						sg->length,
> -						dir,
> -						attrs);
> -			sg->dma_address = dev_addr;
> -		} else {
> -			/* we are not interested in the dma_addr returned by
> -			 * xen_dma_map_page, only in the potential cache flushes executed
> -			 * by the function. */
> -			xen_dma_map_page(hwdev, pfn_to_page(paddr >> PAGE_SHIFT),
> -						dev_addr,
> -						paddr & ~PAGE_MASK,
> -						sg->length,
> -						dir,
> -						attrs);
> -			sg->dma_address = dev_addr;
> -		}
> +		sg->dma_address = xen_swiotlb_map_page(dev, sg_page(sg),
> +				sg->offset, sg->length, dir, attrs);
> +		if (sg->dma_address == DMA_MAPPING_ERROR)
> +			goto out_unmap;
>  		sg_dma_len(sg) = sg->length;
>  	}
> +
>  	return nelems;
> +out_unmap:
> +	xen_swiotlb_unmap_sg(dev, sgl, i, dir, attrs | DMA_ATTR_SKIP_CPU_SYNC);
> +	sg_dma_len(sgl) = 0;
> +	return 0;
>  }
>  
>  /*
> -- 
> 2.20.1
> 
_______________________________________________
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iommu@lists.linux-foundation.org
https://lists.linuxfoundation.org/mailman/listinfo/iommu

[PATCH 3/4] swiotlb-xen: simplify the DMA sync method implementations

[Christoph Hellwig]

Get rid of the grand multiplexer and implement the sync_single_for_cpu
and sync_single_for_device methods directly, and then loop over them
for the scatterlist based variants.

Note that this also loses a few comments related to highlevel DMA API
concepts, which have nothing to do with the swiotlb-xen implementation
details.

Signed-off-by: Christoph Hellwig <hch-jcswGhMUV9g@public.gmane.org>
---
 drivers/xen/swiotlb-xen.c | 84 +++++++++++++--------------------------
 1 file changed, 28 insertions(+), 56 deletions(-)

diff --git a/drivers/xen/swiotlb-xen.c b/drivers/xen/swiotlb-xen.c
index 97a55c225593..9a951504dc12 100644
--- a/drivers/xen/swiotlb-xen.c
+++ b/drivers/xen/swiotlb-xen.c
@@ -455,48 +455,28 @@ static void xen_swiotlb_unmap_page(struct device *hwdev, dma_addr_t dev_addr,
 	xen_unmap_single(hwdev, dev_addr, size, dir, attrs);
 }
 
-/*
- * Make physical memory consistent for a single streaming mode DMA translation
- * after a transfer.
- *
- * If you perform a xen_swiotlb_map_page() but wish to interrogate the buffer
- * using the cpu, yet do not wish to teardown the dma mapping, you must
- * call this function before doing so.  At the next point you give the dma
- * address back to the card, you must first perform a
- * xen_swiotlb_dma_sync_for_device, and then the device again owns the buffer
- */
 static void
-xen_swiotlb_sync_single(struct device *hwdev, dma_addr_t dev_addr,
-			size_t size, enum dma_data_direction dir,
-			enum dma_sync_target target)
+xen_swiotlb_sync_single_for_cpu(struct device *dev, dma_addr_t dma_addr,
+		size_t size, enum dma_data_direction dir)
 {
-	phys_addr_t paddr = xen_bus_to_phys(dev_addr);
+	phys_addr_t paddr = xen_bus_to_phys(dma_addr);
 
-	BUG_ON(dir == DMA_NONE);
-
-	if (target == SYNC_FOR_CPU)
-		xen_dma_sync_single_for_cpu(hwdev, dev_addr, size, dir);
+	xen_dma_sync_single_for_cpu(dev, dma_addr, size, dir);
 
-	/* NOTE: We use dev_addr here, not paddr! */
-	if (is_xen_swiotlb_buffer(dev_addr))
-		swiotlb_tbl_sync_single(hwdev, paddr, size, dir, target);
-
-	if (target == SYNC_FOR_DEVICE)
-		xen_dma_sync_single_for_device(hwdev, dev_addr, size, dir);
+	if (is_xen_swiotlb_buffer(dma_addr))
+		swiotlb_tbl_sync_single(dev, paddr, size, dir, SYNC_FOR_CPU);
 }
 
-void
-xen_swiotlb_sync_single_for_cpu(struct device *hwdev, dma_addr_t dev_addr,
-				size_t size, enum dma_data_direction dir)
+static void
+xen_swiotlb_sync_single_for_device(struct device *dev, dma_addr_t dma_addr,
+		size_t size, enum dma_data_direction dir)
 {
-	xen_swiotlb_sync_single(hwdev, dev_addr, size, dir, SYNC_FOR_CPU);
-}
+	phys_addr_t paddr = xen_bus_to_phys(dma_addr);
 
-void
-xen_swiotlb_sync_single_for_device(struct device *hwdev, dma_addr_t dev_addr,
-				   size_t size, enum dma_data_direction dir)
-{
-	xen_swiotlb_sync_single(hwdev, dev_addr, size, dir, SYNC_FOR_DEVICE);
+	if (is_xen_swiotlb_buffer(dma_addr))
+		swiotlb_tbl_sync_single(dev, paddr, size, dir, SYNC_FOR_DEVICE);
+
+	xen_dma_sync_single_for_device(dev, dma_addr, size, dir);
 }
 
 /*
@@ -541,38 +521,30 @@ xen_swiotlb_map_sg(struct device *dev, struct scatterlist *sgl, int nelems,
 	return 0;
 }
 
-/*
- * Make physical memory consistent for a set of streaming mode DMA translations
- * after a transfer.
- *
- * The same as swiotlb_sync_single_* but for a scatter-gather list, same rules
- * and usage.
- */
 static void
-xen_swiotlb_sync_sg(struct device *hwdev, struct scatterlist *sgl,
-		    int nelems, enum dma_data_direction dir,
-		    enum dma_sync_target target)
+xen_swiotlb_sync_sg_for_cpu(struct device *dev, struct scatterlist *sgl,
+			    int nelems, enum dma_data_direction dir)
 {
 	struct scatterlist *sg;
 	int i;
 
-	for_each_sg(sgl, sg, nelems, i)
-		xen_swiotlb_sync_single(hwdev, sg->dma_address,
-					sg_dma_len(sg), dir, target);
-}
-
-static void
-xen_swiotlb_sync_sg_for_cpu(struct device *hwdev, struct scatterlist *sg,
-			    int nelems, enum dma_data_direction dir)
-{
-	xen_swiotlb_sync_sg(hwdev, sg, nelems, dir, SYNC_FOR_CPU);
+	for_each_sg(sgl, sg, nelems, i) {
+		xen_swiotlb_sync_single_for_cpu(dev, sg->dma_address,
+				sg->length, dir);
+	}
 }
 
 static void
-xen_swiotlb_sync_sg_for_device(struct device *hwdev, struct scatterlist *sg,
+xen_swiotlb_sync_sg_for_device(struct device *dev, struct scatterlist *sgl,
 			       int nelems, enum dma_data_direction dir)
 {
-	xen_swiotlb_sync_sg(hwdev, sg, nelems, dir, SYNC_FOR_DEVICE);
+	struct scatterlist *sg;
+	int i;
+
+	for_each_sg(sgl, sg, nelems, i) {
+		xen_swiotlb_sync_single_for_device(dev, sg->dma_address,
+				sg->length, dir);
+	}
 }
 
 /*
-- 
2.20.1

[PATCH 3/4] swiotlb-xen: simplify the DMA sync method implementations

[Christoph Hellwig]

Get rid of the grand multiplexer and implement the sync_single_for_cpu
and sync_single_for_device methods directly, and then loop over them
for the scatterlist based variants.

Note that this also loses a few comments related to highlevel DMA API
concepts, which have nothing to do with the swiotlb-xen implementation
details.

Signed-off-by: Christoph Hellwig <hch@lst.de>
---
 drivers/xen/swiotlb-xen.c | 84 +++++++++++++--------------------------
 1 file changed, 28 insertions(+), 56 deletions(-)

diff --git a/drivers/xen/swiotlb-xen.c b/drivers/xen/swiotlb-xen.c
index 97a55c225593..9a951504dc12 100644
--- a/drivers/xen/swiotlb-xen.c
+++ b/drivers/xen/swiotlb-xen.c
@@ -455,48 +455,28 @@ static void xen_swiotlb_unmap_page(struct device *hwdev, dma_addr_t dev_addr,
 	xen_unmap_single(hwdev, dev_addr, size, dir, attrs);
 }
 
-/*
- * Make physical memory consistent for a single streaming mode DMA translation
- * after a transfer.
- *
- * If you perform a xen_swiotlb_map_page() but wish to interrogate the buffer
- * using the cpu, yet do not wish to teardown the dma mapping, you must
- * call this function before doing so.  At the next point you give the dma
- * address back to the card, you must first perform a
- * xen_swiotlb_dma_sync_for_device, and then the device again owns the buffer
- */
 static void
-xen_swiotlb_sync_single(struct device *hwdev, dma_addr_t dev_addr,
-			size_t size, enum dma_data_direction dir,
-			enum dma_sync_target target)
+xen_swiotlb_sync_single_for_cpu(struct device *dev, dma_addr_t dma_addr,
+		size_t size, enum dma_data_direction dir)
 {
-	phys_addr_t paddr = xen_bus_to_phys(dev_addr);
+	phys_addr_t paddr = xen_bus_to_phys(dma_addr);
 
-	BUG_ON(dir == DMA_NONE);
-
-	if (target == SYNC_FOR_CPU)
-		xen_dma_sync_single_for_cpu(hwdev, dev_addr, size, dir);
+	xen_dma_sync_single_for_cpu(dev, dma_addr, size, dir);
 
-	/* NOTE: We use dev_addr here, not paddr! */
-	if (is_xen_swiotlb_buffer(dev_addr))
-		swiotlb_tbl_sync_single(hwdev, paddr, size, dir, target);
-
-	if (target == SYNC_FOR_DEVICE)
-		xen_dma_sync_single_for_device(hwdev, dev_addr, size, dir);
+	if (is_xen_swiotlb_buffer(dma_addr))
+		swiotlb_tbl_sync_single(dev, paddr, size, dir, SYNC_FOR_CPU);
 }
 
-void
-xen_swiotlb_sync_single_for_cpu(struct device *hwdev, dma_addr_t dev_addr,
-				size_t size, enum dma_data_direction dir)
+static void
+xen_swiotlb_sync_single_for_device(struct device *dev, dma_addr_t dma_addr,
+		size_t size, enum dma_data_direction dir)
 {
-	xen_swiotlb_sync_single(hwdev, dev_addr, size, dir, SYNC_FOR_CPU);
-}
+	phys_addr_t paddr = xen_bus_to_phys(dma_addr);
 
-void
-xen_swiotlb_sync_single_for_device(struct device *hwdev, dma_addr_t dev_addr,
-				   size_t size, enum dma_data_direction dir)
-{
-	xen_swiotlb_sync_single(hwdev, dev_addr, size, dir, SYNC_FOR_DEVICE);
+	if (is_xen_swiotlb_buffer(dma_addr))
+		swiotlb_tbl_sync_single(dev, paddr, size, dir, SYNC_FOR_DEVICE);
+
+	xen_dma_sync_single_for_device(dev, dma_addr, size, dir);
 }
 
 /*
@@ -541,38 +521,30 @@ xen_swiotlb_map_sg(struct device *dev, struct scatterlist *sgl, int nelems,
 	return 0;
 }
 
-/*
- * Make physical memory consistent for a set of streaming mode DMA translations
- * after a transfer.
- *
- * The same as swiotlb_sync_single_* but for a scatter-gather list, same rules
- * and usage.
- */
 static void
-xen_swiotlb_sync_sg(struct device *hwdev, struct scatterlist *sgl,
-		    int nelems, enum dma_data_direction dir,
-		    enum dma_sync_target target)
+xen_swiotlb_sync_sg_for_cpu(struct device *dev, struct scatterlist *sgl,
+			    int nelems, enum dma_data_direction dir)
 {
 	struct scatterlist *sg;
 	int i;
 
-	for_each_sg(sgl, sg, nelems, i)
-		xen_swiotlb_sync_single(hwdev, sg->dma_address,
-					sg_dma_len(sg), dir, target);
-}
-
-static void
-xen_swiotlb_sync_sg_for_cpu(struct device *hwdev, struct scatterlist *sg,
-			    int nelems, enum dma_data_direction dir)
-{
-	xen_swiotlb_sync_sg(hwdev, sg, nelems, dir, SYNC_FOR_CPU);
+	for_each_sg(sgl, sg, nelems, i) {
+		xen_swiotlb_sync_single_for_cpu(dev, sg->dma_address,
+				sg->length, dir);
+	}
 }
 
 static void
-xen_swiotlb_sync_sg_for_device(struct device *hwdev, struct scatterlist *sg,
+xen_swiotlb_sync_sg_for_device(struct device *dev, struct scatterlist *sgl,
 			       int nelems, enum dma_data_direction dir)
 {
-	xen_swiotlb_sync_sg(hwdev, sg, nelems, dir, SYNC_FOR_DEVICE);
+	struct scatterlist *sg;
+	int i;
+
+	for_each_sg(sgl, sg, nelems, i) {
+		xen_swiotlb_sync_single_for_device(dev, sg->dma_address,
+				sg->length, dir);
+	}
 }
 
 /*
-- 
2.20.1

_______________________________________________
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https://lists.linuxfoundation.org/mailman/listinfo/iommu

Re: [PATCH 3/4] swiotlb-xen: simplify the DMA sync method implementations

[Stefano Stabellini]

On Thu, 11 Apr 2019, Christoph Hellwig wrote:
> Get rid of the grand multiplexer and implement the sync_single_for_cpu
> and sync_single_for_device methods directly, and then loop over them
> for the scatterlist based variants.
> 
> Note that this also loses a few comments related to highlevel DMA API
> concepts, which have nothing to do with the swiotlb-xen implementation
> details.
> 
> Signed-off-by: Christoph Hellwig <hch-jcswGhMUV9g@public.gmane.org>

Reviewed-by: Stefano Stabellini <sstabellini-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org>

> ---
>  drivers/xen/swiotlb-xen.c | 84 +++++++++++++--------------------------
>  1 file changed, 28 insertions(+), 56 deletions(-)
> 
> diff --git a/drivers/xen/swiotlb-xen.c b/drivers/xen/swiotlb-xen.c
> index 97a55c225593..9a951504dc12 100644
> --- a/drivers/xen/swiotlb-xen.c
> +++ b/drivers/xen/swiotlb-xen.c
> @@ -455,48 +455,28 @@ static void xen_swiotlb_unmap_page(struct device *hwdev, dma_addr_t dev_addr,
>  	xen_unmap_single(hwdev, dev_addr, size, dir, attrs);
>  }
>  
> -/*
> - * Make physical memory consistent for a single streaming mode DMA translation
> - * after a transfer.
> - *
> - * If you perform a xen_swiotlb_map_page() but wish to interrogate the buffer
> - * using the cpu, yet do not wish to teardown the dma mapping, you must
> - * call this function before doing so.  At the next point you give the dma
> - * address back to the card, you must first perform a
> - * xen_swiotlb_dma_sync_for_device, and then the device again owns the buffer
> - */
>  static void
> -xen_swiotlb_sync_single(struct device *hwdev, dma_addr_t dev_addr,
> -			size_t size, enum dma_data_direction dir,
> -			enum dma_sync_target target)
> +xen_swiotlb_sync_single_for_cpu(struct device *dev, dma_addr_t dma_addr,
> +		size_t size, enum dma_data_direction dir)
>  {
> -	phys_addr_t paddr = xen_bus_to_phys(dev_addr);
> +	phys_addr_t paddr = xen_bus_to_phys(dma_addr);
>  
> -	BUG_ON(dir == DMA_NONE);
> -
> -	if (target == SYNC_FOR_CPU)
> -		xen_dma_sync_single_for_cpu(hwdev, dev_addr, size, dir);
> +	xen_dma_sync_single_for_cpu(dev, dma_addr, size, dir);
>  
> -	/* NOTE: We use dev_addr here, not paddr! */
> -	if (is_xen_swiotlb_buffer(dev_addr))
> -		swiotlb_tbl_sync_single(hwdev, paddr, size, dir, target);
> -
> -	if (target == SYNC_FOR_DEVICE)
> -		xen_dma_sync_single_for_device(hwdev, dev_addr, size, dir);
> +	if (is_xen_swiotlb_buffer(dma_addr))
> +		swiotlb_tbl_sync_single(dev, paddr, size, dir, SYNC_FOR_CPU);
>  }
>  
> -void
> -xen_swiotlb_sync_single_for_cpu(struct device *hwdev, dma_addr_t dev_addr,
> -				size_t size, enum dma_data_direction dir)
> +static void
> +xen_swiotlb_sync_single_for_device(struct device *dev, dma_addr_t dma_addr,
> +		size_t size, enum dma_data_direction dir)
>  {
> -	xen_swiotlb_sync_single(hwdev, dev_addr, size, dir, SYNC_FOR_CPU);
> -}
> +	phys_addr_t paddr = xen_bus_to_phys(dma_addr);
>  
> -void
> -xen_swiotlb_sync_single_for_device(struct device *hwdev, dma_addr_t dev_addr,
> -				   size_t size, enum dma_data_direction dir)
> -{
> -	xen_swiotlb_sync_single(hwdev, dev_addr, size, dir, SYNC_FOR_DEVICE);
> +	if (is_xen_swiotlb_buffer(dma_addr))
> +		swiotlb_tbl_sync_single(dev, paddr, size, dir, SYNC_FOR_DEVICE);
> +
> +	xen_dma_sync_single_for_device(dev, dma_addr, size, dir);
>  }
>  
>  /*
> @@ -541,38 +521,30 @@ xen_swiotlb_map_sg(struct device *dev, struct scatterlist *sgl, int nelems,
>  	return 0;
>  }
>  
> -/*
> - * Make physical memory consistent for a set of streaming mode DMA translations
> - * after a transfer.
> - *
> - * The same as swiotlb_sync_single_* but for a scatter-gather list, same rules
> - * and usage.
> - */
>  static void
> -xen_swiotlb_sync_sg(struct device *hwdev, struct scatterlist *sgl,
> -		    int nelems, enum dma_data_direction dir,
> -		    enum dma_sync_target target)
> +xen_swiotlb_sync_sg_for_cpu(struct device *dev, struct scatterlist *sgl,
> +			    int nelems, enum dma_data_direction dir)
>  {
>  	struct scatterlist *sg;
>  	int i;
>  
> -	for_each_sg(sgl, sg, nelems, i)
> -		xen_swiotlb_sync_single(hwdev, sg->dma_address,
> -					sg_dma_len(sg), dir, target);
> -}
> -
> -static void
> -xen_swiotlb_sync_sg_for_cpu(struct device *hwdev, struct scatterlist *sg,
> -			    int nelems, enum dma_data_direction dir)
> -{
> -	xen_swiotlb_sync_sg(hwdev, sg, nelems, dir, SYNC_FOR_CPU);
> +	for_each_sg(sgl, sg, nelems, i) {
> +		xen_swiotlb_sync_single_for_cpu(dev, sg->dma_address,
> +				sg->length, dir);
> +	}
>  }
>  
>  static void
> -xen_swiotlb_sync_sg_for_device(struct device *hwdev, struct scatterlist *sg,
> +xen_swiotlb_sync_sg_for_device(struct device *dev, struct scatterlist *sgl,
>  			       int nelems, enum dma_data_direction dir)
>  {
> -	xen_swiotlb_sync_sg(hwdev, sg, nelems, dir, SYNC_FOR_DEVICE);
> +	struct scatterlist *sg;
> +	int i;
> +
> +	for_each_sg(sgl, sg, nelems, i) {
> +		xen_swiotlb_sync_single_for_device(dev, sg->dma_address,
> +				sg->length, dir);
> +	}
>  }

Re: [PATCH 3/4] swiotlb-xen: simplify the DMA sync method implementations

[Stefano Stabellini]

On Thu, 11 Apr 2019, Christoph Hellwig wrote:
> Get rid of the grand multiplexer and implement the sync_single_for_cpu
> and sync_single_for_device methods directly, and then loop over them
> for the scatterlist based variants.
> 
> Note that this also loses a few comments related to highlevel DMA API
> concepts, which have nothing to do with the swiotlb-xen implementation
> details.
> 
> Signed-off-by: Christoph Hellwig <hch@lst.de>

Reviewed-by: Stefano Stabellini <sstabellini@kernel.org>

> ---
>  drivers/xen/swiotlb-xen.c | 84 +++++++++++++--------------------------
>  1 file changed, 28 insertions(+), 56 deletions(-)
> 
> diff --git a/drivers/xen/swiotlb-xen.c b/drivers/xen/swiotlb-xen.c
> index 97a55c225593..9a951504dc12 100644
> --- a/drivers/xen/swiotlb-xen.c
> +++ b/drivers/xen/swiotlb-xen.c
> @@ -455,48 +455,28 @@ static void xen_swiotlb_unmap_page(struct device *hwdev, dma_addr_t dev_addr,
>  	xen_unmap_single(hwdev, dev_addr, size, dir, attrs);
>  }
>  
> -/*
> - * Make physical memory consistent for a single streaming mode DMA translation
> - * after a transfer.
> - *
> - * If you perform a xen_swiotlb_map_page() but wish to interrogate the buffer
> - * using the cpu, yet do not wish to teardown the dma mapping, you must
> - * call this function before doing so.  At the next point you give the dma
> - * address back to the card, you must first perform a
> - * xen_swiotlb_dma_sync_for_device, and then the device again owns the buffer
> - */
>  static void
> -xen_swiotlb_sync_single(struct device *hwdev, dma_addr_t dev_addr,
> -			size_t size, enum dma_data_direction dir,
> -			enum dma_sync_target target)
> +xen_swiotlb_sync_single_for_cpu(struct device *dev, dma_addr_t dma_addr,
> +		size_t size, enum dma_data_direction dir)
>  {
> -	phys_addr_t paddr = xen_bus_to_phys(dev_addr);
> +	phys_addr_t paddr = xen_bus_to_phys(dma_addr);
>  
> -	BUG_ON(dir == DMA_NONE);
> -
> -	if (target == SYNC_FOR_CPU)
> -		xen_dma_sync_single_for_cpu(hwdev, dev_addr, size, dir);
> +	xen_dma_sync_single_for_cpu(dev, dma_addr, size, dir);
>  
> -	/* NOTE: We use dev_addr here, not paddr! */
> -	if (is_xen_swiotlb_buffer(dev_addr))
> -		swiotlb_tbl_sync_single(hwdev, paddr, size, dir, target);
> -
> -	if (target == SYNC_FOR_DEVICE)
> -		xen_dma_sync_single_for_device(hwdev, dev_addr, size, dir);
> +	if (is_xen_swiotlb_buffer(dma_addr))
> +		swiotlb_tbl_sync_single(dev, paddr, size, dir, SYNC_FOR_CPU);
>  }
>  
> -void
> -xen_swiotlb_sync_single_for_cpu(struct device *hwdev, dma_addr_t dev_addr,
> -				size_t size, enum dma_data_direction dir)
> +static void
> +xen_swiotlb_sync_single_for_device(struct device *dev, dma_addr_t dma_addr,
> +		size_t size, enum dma_data_direction dir)
>  {
> -	xen_swiotlb_sync_single(hwdev, dev_addr, size, dir, SYNC_FOR_CPU);
> -}
> +	phys_addr_t paddr = xen_bus_to_phys(dma_addr);
>  
> -void
> -xen_swiotlb_sync_single_for_device(struct device *hwdev, dma_addr_t dev_addr,
> -				   size_t size, enum dma_data_direction dir)
> -{
> -	xen_swiotlb_sync_single(hwdev, dev_addr, size, dir, SYNC_FOR_DEVICE);
> +	if (is_xen_swiotlb_buffer(dma_addr))
> +		swiotlb_tbl_sync_single(dev, paddr, size, dir, SYNC_FOR_DEVICE);
> +
> +	xen_dma_sync_single_for_device(dev, dma_addr, size, dir);
>  }
>  
>  /*
> @@ -541,38 +521,30 @@ xen_swiotlb_map_sg(struct device *dev, struct scatterlist *sgl, int nelems,
>  	return 0;
>  }
>  
> -/*
> - * Make physical memory consistent for a set of streaming mode DMA translations
> - * after a transfer.
> - *
> - * The same as swiotlb_sync_single_* but for a scatter-gather list, same rules
> - * and usage.
> - */
>  static void
> -xen_swiotlb_sync_sg(struct device *hwdev, struct scatterlist *sgl,
> -		    int nelems, enum dma_data_direction dir,
> -		    enum dma_sync_target target)
> +xen_swiotlb_sync_sg_for_cpu(struct device *dev, struct scatterlist *sgl,
> +			    int nelems, enum dma_data_direction dir)
>  {
>  	struct scatterlist *sg;
>  	int i;
>  
> -	for_each_sg(sgl, sg, nelems, i)
> -		xen_swiotlb_sync_single(hwdev, sg->dma_address,
> -					sg_dma_len(sg), dir, target);
> -}
> -
> -static void
> -xen_swiotlb_sync_sg_for_cpu(struct device *hwdev, struct scatterlist *sg,
> -			    int nelems, enum dma_data_direction dir)
> -{
> -	xen_swiotlb_sync_sg(hwdev, sg, nelems, dir, SYNC_FOR_CPU);
> +	for_each_sg(sgl, sg, nelems, i) {
> +		xen_swiotlb_sync_single_for_cpu(dev, sg->dma_address,
> +				sg->length, dir);
> +	}
>  }
>  
>  static void
> -xen_swiotlb_sync_sg_for_device(struct device *hwdev, struct scatterlist *sg,
> +xen_swiotlb_sync_sg_for_device(struct device *dev, struct scatterlist *sgl,
>  			       int nelems, enum dma_data_direction dir)
>  {
> -	xen_swiotlb_sync_sg(hwdev, sg, nelems, dir, SYNC_FOR_DEVICE);
> +	struct scatterlist *sg;
> +	int i;
> +
> +	for_each_sg(sgl, sg, nelems, i) {
> +		xen_swiotlb_sync_single_for_device(dev, sg->dma_address,
> +				sg->length, dir);
> +	}
>  }
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[PATCH 4/4] swiotlb-xen: ensure we have a single callsite for xen_dma_map_page

[Christoph Hellwig]

Refactor the code a bit to make further changes easier.

Signed-off-by: Christoph Hellwig <hch-jcswGhMUV9g@public.gmane.org>
---
 drivers/xen/swiotlb-xen.c | 31 ++++++++++++++++---------------
 1 file changed, 16 insertions(+), 15 deletions(-)

diff --git a/drivers/xen/swiotlb-xen.c b/drivers/xen/swiotlb-xen.c
index 9a951504dc12..5dcb06fe9667 100644
--- a/drivers/xen/swiotlb-xen.c
+++ b/drivers/xen/swiotlb-xen.c
@@ -391,13 +391,8 @@ static dma_addr_t xen_swiotlb_map_page(struct device *dev, struct page *page,
 	if (dma_capable(dev, dev_addr, size) &&
 	    !range_straddles_page_boundary(phys, size) &&
 		!xen_arch_need_swiotlb(dev, phys, dev_addr) &&
-		(swiotlb_force != SWIOTLB_FORCE)) {
-		/* we are not interested in the dma_addr returned by
-		 * xen_dma_map_page, only in the potential cache flushes executed
-		 * by the function. */
-		xen_dma_map_page(dev, page, dev_addr, offset, size, dir, attrs);
-		return dev_addr;
-	}
+		swiotlb_force != SWIOTLB_FORCE)
+		goto done;
 
 	/*
 	 * Oh well, have to allocate and map a bounce buffer.
@@ -410,19 +405,25 @@ static dma_addr_t xen_swiotlb_map_page(struct device *dev, struct page *page,
 		return DMA_MAPPING_ERROR;
 
 	dev_addr = xen_phys_to_bus(map);
-	xen_dma_map_page(dev, pfn_to_page(map >> PAGE_SHIFT),
-					dev_addr, map & ~PAGE_MASK, size, dir, attrs);
 
 	/*
 	 * Ensure that the address returned is DMA'ble
 	 */
-	if (dma_capable(dev, dev_addr, size))
-		return dev_addr;
-
-	attrs |= DMA_ATTR_SKIP_CPU_SYNC;
-	swiotlb_tbl_unmap_single(dev, map, size, dir, attrs);
+	if (unlikely(!dma_capable(dev, dev_addr, size))) {
+		swiotlb_tbl_unmap_single(dev, map, size, dir,
+				attrs | DMA_ATTR_SKIP_CPU_SYNC);
+		return DMA_MAPPING_ERROR;
+	}
 
-	return DMA_MAPPING_ERROR;
+	page = pfn_to_page(map >> PAGE_SHIFT);
+	offset = map & ~PAGE_MASK;
+done:
+	/*
+	 * we are not interested in the dma_addr returned by xen_dma_map_page,
+	 * only in the potential cache flushes executed by the function.
+	 */
+	xen_dma_map_page(dev, page, dev_addr, offset, size, dir, attrs);
+	return dev_addr;
 }
 
 /*
-- 
2.20.1

[PATCH 4/4] swiotlb-xen: ensure we have a single callsite for xen_dma_map_page

[Christoph Hellwig]

Refactor the code a bit to make further changes easier.

Signed-off-by: Christoph Hellwig <hch@lst.de>
---
 drivers/xen/swiotlb-xen.c | 31 ++++++++++++++++---------------
 1 file changed, 16 insertions(+), 15 deletions(-)

diff --git a/drivers/xen/swiotlb-xen.c b/drivers/xen/swiotlb-xen.c
index 9a951504dc12..5dcb06fe9667 100644
--- a/drivers/xen/swiotlb-xen.c
+++ b/drivers/xen/swiotlb-xen.c
@@ -391,13 +391,8 @@ static dma_addr_t xen_swiotlb_map_page(struct device *dev, struct page *page,
 	if (dma_capable(dev, dev_addr, size) &&
 	    !range_straddles_page_boundary(phys, size) &&
 		!xen_arch_need_swiotlb(dev, phys, dev_addr) &&
-		(swiotlb_force != SWIOTLB_FORCE)) {
-		/* we are not interested in the dma_addr returned by
-		 * xen_dma_map_page, only in the potential cache flushes executed
-		 * by the function. */
-		xen_dma_map_page(dev, page, dev_addr, offset, size, dir, attrs);
-		return dev_addr;
-	}
+		swiotlb_force != SWIOTLB_FORCE)
+		goto done;
 
 	/*
 	 * Oh well, have to allocate and map a bounce buffer.
@@ -410,19 +405,25 @@ static dma_addr_t xen_swiotlb_map_page(struct device *dev, struct page *page,
 		return DMA_MAPPING_ERROR;
 
 	dev_addr = xen_phys_to_bus(map);
-	xen_dma_map_page(dev, pfn_to_page(map >> PAGE_SHIFT),
-					dev_addr, map & ~PAGE_MASK, size, dir, attrs);
 
 	/*
 	 * Ensure that the address returned is DMA'ble
 	 */
-	if (dma_capable(dev, dev_addr, size))
-		return dev_addr;
-
-	attrs |= DMA_ATTR_SKIP_CPU_SYNC;
-	swiotlb_tbl_unmap_single(dev, map, size, dir, attrs);
+	if (unlikely(!dma_capable(dev, dev_addr, size))) {
+		swiotlb_tbl_unmap_single(dev, map, size, dir,
+				attrs | DMA_ATTR_SKIP_CPU_SYNC);
+		return DMA_MAPPING_ERROR;
+	}
 
-	return DMA_MAPPING_ERROR;
+	page = pfn_to_page(map >> PAGE_SHIFT);
+	offset = map & ~PAGE_MASK;
+done:
+	/*
+	 * we are not interested in the dma_addr returned by xen_dma_map_page,
+	 * only in the potential cache flushes executed by the function.
+	 */
+	xen_dma_map_page(dev, page, dev_addr, offset, size, dir, attrs);
+	return dev_addr;
 }
 
 /*
-- 
2.20.1

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Re: [PATCH 4/4] swiotlb-xen: ensure we have a single callsite for xen_dma_map_page

[Stefano Stabellini]

On Thu, 11 Apr 2019, Christoph Hellwig wrote:
> Refactor the code a bit to make further changes easier.
> 
> Signed-off-by: Christoph Hellwig <hch-jcswGhMUV9g@public.gmane.org>

Reviewed-by: Stefano Stabellini <sstabellini-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org>

> ---
>  drivers/xen/swiotlb-xen.c | 31 ++++++++++++++++---------------
>  1 file changed, 16 insertions(+), 15 deletions(-)
> 
> diff --git a/drivers/xen/swiotlb-xen.c b/drivers/xen/swiotlb-xen.c
> index 9a951504dc12..5dcb06fe9667 100644
> --- a/drivers/xen/swiotlb-xen.c
> +++ b/drivers/xen/swiotlb-xen.c
> @@ -391,13 +391,8 @@ static dma_addr_t xen_swiotlb_map_page(struct device *dev, struct page *page,
>  	if (dma_capable(dev, dev_addr, size) &&
>  	    !range_straddles_page_boundary(phys, size) &&
>  		!xen_arch_need_swiotlb(dev, phys, dev_addr) &&
> -		(swiotlb_force != SWIOTLB_FORCE)) {
> -		/* we are not interested in the dma_addr returned by
> -		 * xen_dma_map_page, only in the potential cache flushes executed
> -		 * by the function. */
> -		xen_dma_map_page(dev, page, dev_addr, offset, size, dir, attrs);
> -		return dev_addr;
> -	}
> +		swiotlb_force != SWIOTLB_FORCE)
> +		goto done;
>  
>  	/*
>  	 * Oh well, have to allocate and map a bounce buffer.
> @@ -410,19 +405,25 @@ static dma_addr_t xen_swiotlb_map_page(struct device *dev, struct page *page,
>  		return DMA_MAPPING_ERROR;
>  
>  	dev_addr = xen_phys_to_bus(map);
> -	xen_dma_map_page(dev, pfn_to_page(map >> PAGE_SHIFT),
> -					dev_addr, map & ~PAGE_MASK, size, dir, attrs);
>  
>  	/*
>  	 * Ensure that the address returned is DMA'ble
>  	 */
> -	if (dma_capable(dev, dev_addr, size))
> -		return dev_addr;
> -
> -	attrs |= DMA_ATTR_SKIP_CPU_SYNC;
> -	swiotlb_tbl_unmap_single(dev, map, size, dir, attrs);
> +	if (unlikely(!dma_capable(dev, dev_addr, size))) {
> +		swiotlb_tbl_unmap_single(dev, map, size, dir,
> +				attrs | DMA_ATTR_SKIP_CPU_SYNC);
> +		return DMA_MAPPING_ERROR;
> +	}
>  
> -	return DMA_MAPPING_ERROR;
> +	page = pfn_to_page(map >> PAGE_SHIFT);
> +	offset = map & ~PAGE_MASK;
> +done:
> +	/*
> +	 * we are not interested in the dma_addr returned by xen_dma_map_page,
> +	 * only in the potential cache flushes executed by the function.
> +	 */
> +	xen_dma_map_page(dev, page, dev_addr, offset, size, dir, attrs);
> +	return dev_addr;
>  }
>  
>  /*
> -- 
> 2.20.1
> 

Re: [PATCH 4/4] swiotlb-xen: ensure we have a single callsite for xen_dma_map_page

[Stefano Stabellini]

On Thu, 11 Apr 2019, Christoph Hellwig wrote:
> Refactor the code a bit to make further changes easier.
> 
> Signed-off-by: Christoph Hellwig <hch@lst.de>

Reviewed-by: Stefano Stabellini <sstabellini@kernel.org>

> ---
>  drivers/xen/swiotlb-xen.c | 31 ++++++++++++++++---------------
>  1 file changed, 16 insertions(+), 15 deletions(-)
> 
> diff --git a/drivers/xen/swiotlb-xen.c b/drivers/xen/swiotlb-xen.c
> index 9a951504dc12..5dcb06fe9667 100644
> --- a/drivers/xen/swiotlb-xen.c
> +++ b/drivers/xen/swiotlb-xen.c
> @@ -391,13 +391,8 @@ static dma_addr_t xen_swiotlb_map_page(struct device *dev, struct page *page,
>  	if (dma_capable(dev, dev_addr, size) &&
>  	    !range_straddles_page_boundary(phys, size) &&
>  		!xen_arch_need_swiotlb(dev, phys, dev_addr) &&
> -		(swiotlb_force != SWIOTLB_FORCE)) {
> -		/* we are not interested in the dma_addr returned by
> -		 * xen_dma_map_page, only in the potential cache flushes executed
> -		 * by the function. */
> -		xen_dma_map_page(dev, page, dev_addr, offset, size, dir, attrs);
> -		return dev_addr;
> -	}
> +		swiotlb_force != SWIOTLB_FORCE)
> +		goto done;
>  
>  	/*
>  	 * Oh well, have to allocate and map a bounce buffer.
> @@ -410,19 +405,25 @@ static dma_addr_t xen_swiotlb_map_page(struct device *dev, struct page *page,
>  		return DMA_MAPPING_ERROR;
>  
>  	dev_addr = xen_phys_to_bus(map);
> -	xen_dma_map_page(dev, pfn_to_page(map >> PAGE_SHIFT),
> -					dev_addr, map & ~PAGE_MASK, size, dir, attrs);
>  
>  	/*
>  	 * Ensure that the address returned is DMA'ble
>  	 */
> -	if (dma_capable(dev, dev_addr, size))
> -		return dev_addr;
> -
> -	attrs |= DMA_ATTR_SKIP_CPU_SYNC;
> -	swiotlb_tbl_unmap_single(dev, map, size, dir, attrs);
> +	if (unlikely(!dma_capable(dev, dev_addr, size))) {
> +		swiotlb_tbl_unmap_single(dev, map, size, dir,
> +				attrs | DMA_ATTR_SKIP_CPU_SYNC);
> +		return DMA_MAPPING_ERROR;
> +	}
>  
> -	return DMA_MAPPING_ERROR;
> +	page = pfn_to_page(map >> PAGE_SHIFT);
> +	offset = map & ~PAGE_MASK;
> +done:
> +	/*
> +	 * we are not interested in the dma_addr returned by xen_dma_map_page,
> +	 * only in the potential cache flushes executed by the function.
> +	 */
> +	xen_dma_map_page(dev, page, dev_addr, offset, size, dir, attrs);
> +	return dev_addr;
>  }
>  
>  /*
> -- 
> 2.20.1
> 
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Re: a few xen swiotlb cleanups

[Konrad Rzeszutek Wilk]

On Thu, Apr 11, 2019 at 09:19:56AM +0200, Christoph Hellwig wrote:
> Hi all,

I will slurp these up.. right after I test them for correctness.

> 
> below are a couple of cleanups for swiotlb-xen.c.  They were done in
> preparation of eventually using the dma-noncoherent.h cache flushing
> hooks, but that final goal will need some major work to the arm32 code
> first.  Until then I think these patches might be better in mainline
> than in my local tree so that they don't bitrot.

Re: a few xen swiotlb cleanups

[Konrad Rzeszutek Wilk]

On Thu, Apr 11, 2019 at 09:19:56AM +0200, Christoph Hellwig wrote:
> Hi all,

I will slurp these up.. right after I test them for correctness.

> 
> below are a couple of cleanups for swiotlb-xen.c.  They were done in
> preparation of eventually using the dma-noncoherent.h cache flushing
> hooks, but that final goal will need some major work to the arm32 code
> first.  Until then I think these patches might be better in mainline
> than in my local tree so that they don't bitrot.
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