netdev - [swiotlb PATCH v3 2/3] swiotlb-xen: Enforce return of DMA_ERROR

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Message-ID: <20161109152015.25151.73103.stgit@ahduyck-blue-test.jf.intel.com>
Date:   Wed, 09 Nov 2016 10:20:34 -0500
From:   Alexander Duyck <alexander.h.duyck@...el.com>
To:     linux-mm@...ck.org, konrad.wilk@...cle.com
Cc:     netdev@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: [swiotlb PATCH v3 2/3] swiotlb-xen: Enforce return of
 DMA_ERROR_CODE in mapping function

The mapping function should always return DMA_ERROR_CODE when a mapping has
failed as this is what the DMA API expects when a DMA error has occurred.
The current function for mapping a page in Xen was returning either
DMA_ERROR_CODE or 0 depending on where it failed.

On x86 DMA_ERROR_CODE is 0, but on other architectures such as ARM it is
~0. We need to make sure we return the same error value if either the
mapping failed or the device is not capable of accessing the mapping.

If we are returning DMA_ERROR_CODE as our error value we can drop the
function for checking the error code as the default is to compare the
return value against DMA_ERROR_CODE if no function is defined.

Signed-off-by: Alexander Duyck <alexander.h.duyck@...el.com>
---

v1: Added this patch which was part of an earlier patch.
v3: Undid changes to xen_swiotlb_map_page and only changed return value

 arch/arm/xen/mm.c              |    1 -
 arch/x86/xen/pci-swiotlb-xen.c |    1 -
 drivers/xen/swiotlb-xen.c      |    9 +--------
 include/xen/swiotlb-xen.h      |    3 ---
 4 files changed, 1 insertion(+), 13 deletions(-)

diff --git a/arch/arm/xen/mm.c b/arch/arm/xen/mm.c
index d062f08..bd62d94 100644
--- a/arch/arm/xen/mm.c
+++ b/arch/arm/xen/mm.c
@@ -186,7 +186,6 @@ struct dma_map_ops *xen_dma_ops;
 EXPORT_SYMBOL(xen_dma_ops);
 
 static struct dma_map_ops xen_swiotlb_dma_ops = {
-	.mapping_error = xen_swiotlb_dma_mapping_error,
 	.alloc = xen_swiotlb_alloc_coherent,
 	.free = xen_swiotlb_free_coherent,
 	.sync_single_for_cpu = xen_swiotlb_sync_single_for_cpu,
diff --git a/arch/x86/xen/pci-swiotlb-xen.c b/arch/x86/xen/pci-swiotlb-xen.c
index 0e98e5d..a9fafb5 100644
--- a/arch/x86/xen/pci-swiotlb-xen.c
+++ b/arch/x86/xen/pci-swiotlb-xen.c
@@ -19,7 +19,6 @@
 int xen_swiotlb __read_mostly;
 
 static struct dma_map_ops xen_swiotlb_dma_ops = {
-	.mapping_error = xen_swiotlb_dma_mapping_error,
 	.alloc = xen_swiotlb_alloc_coherent,
 	.free = xen_swiotlb_free_coherent,
 	.sync_single_for_cpu = xen_swiotlb_sync_single_for_cpu,
diff --git a/drivers/xen/swiotlb-xen.c b/drivers/xen/swiotlb-xen.c
index 87e6035..c36caa5 100644
--- a/drivers/xen/swiotlb-xen.c
+++ b/drivers/xen/swiotlb-xen.c
@@ -418,7 +418,7 @@ dma_addr_t xen_swiotlb_map_page(struct device *dev, struct page *page,
 	 */
 	if (!dma_capable(dev, dev_addr, size)) {
 		swiotlb_tbl_unmap_single(dev, map, size, dir);
-		dev_addr = 0;
+		return DMA_ERROR_CODE;
 	}
 	return dev_addr;
 }
@@ -648,13 +648,6 @@ xen_swiotlb_sync_sg_for_device(struct device *hwdev, struct scatterlist *sg,
 }
 EXPORT_SYMBOL_GPL(xen_swiotlb_sync_sg_for_device);
 
-int
-xen_swiotlb_dma_mapping_error(struct device *hwdev, dma_addr_t dma_addr)
-{
-	return !dma_addr;
-}
-EXPORT_SYMBOL_GPL(xen_swiotlb_dma_mapping_error);
-
 /*
  * Return whether the given device DMA address mask can be supported
  * properly.  For example, if your device can only drive the low 24-bits
diff --git a/include/xen/swiotlb-xen.h b/include/xen/swiotlb-xen.h
index 7c35e27..a0083be 100644
--- a/include/xen/swiotlb-xen.h
+++ b/include/xen/swiotlb-xen.h
@@ -51,9 +51,6 @@ xen_swiotlb_sync_sg_for_device(struct device *hwdev, struct scatterlist *sg,
 			       int nelems, enum dma_data_direction dir);
 
 extern int
-xen_swiotlb_dma_mapping_error(struct device *hwdev, dma_addr_t dma_addr);
-
-extern int
 xen_swiotlb_dma_supported(struct device *hwdev, u64 mask);
 
 extern int