[PATCH v5 04/13] DMA-API: Introduce dma_(un)map_peer_resource

[PATCH v5 04/13] DMA-API: Introduce dma_(un)map_peer_resource

[Will Davis]

Add functions to DMA-map and -unmap a peer device's resource for a given
device. This will allow devices to DMA-map, for example, another device's
BAR region on PCI to enable peer-to-peer transactions.

Guard these new functions behind CONFIG_HAS_DMA_P2P.

Signed-off-by: Will Davis <wdavis@nvidia.com>
---
 include/asm-generic/dma-mapping-common.h | 43 ++++++++++++++++++++++++++++++++
 include/linux/dma-mapping.h              | 12 +++++++++
 2 files changed, 55 insertions(+)

diff --git a/include/asm-generic/dma-mapping-common.h b/include/asm-generic/dma-mapping-common.h
index 940d5ec..45eec17 100644
--- a/include/asm-generic/dma-mapping-common.h
+++ b/include/asm-generic/dma-mapping-common.h
@@ -73,6 +73,42 @@ static inline void dma_unmap_sg_attrs(struct device *dev, struct scatterlist *sg
 		ops->unmap_sg(dev, sg, nents, dir, attrs);
 }
 
+#ifdef CONFIG_HAS_DMA_P2P
+static inline dma_peer_addr_t dma_map_peer_resource_attrs(struct device *dev,
+							  struct device *peer,
+							  struct resource *res,
+							  size_t offset,
+							  size_t size,
+							  enum dma_data_direction dir,
+							  struct dma_attrs *attrs)
+{
+	struct dma_map_ops *ops = get_dma_ops(dev);
+	dma_peer_addr_t addr;
+
+	BUG_ON(!valid_dma_direction(dir));
+	BUG_ON(ops->map_peer_resource == NULL);
+	addr = ops->map_peer_resource(dev, peer, res, offset, size, dir,
+				      attrs);
+	debug_dma_map_peer_resource(dev, peer, res, offset, size, dir, addr);
+
+	return addr;
+}
+
+static inline void dma_unmap_peer_resource_attrs(struct device *dev,
+						 dma_peer_addr_t addr,
+						 size_t size,
+						 enum dma_data_direction dir,
+						 struct dma_attrs *attrs)
+{
+	struct dma_map_ops *ops = get_dma_ops(dev);
+
+	BUG_ON(!valid_dma_direction(dir));
+	if (ops->unmap_peer_resource)
+		ops->unmap_peer_resource(dev, addr, size, dir, attrs);
+	debug_dma_unmap_peer_resource(dev, addr, size, dir);
+}
+#endif
+
 static inline dma_addr_t dma_map_page(struct device *dev, struct page *page,
 				      size_t offset, size_t size,
 				      enum dma_data_direction dir)
@@ -181,6 +217,13 @@ dma_sync_sg_for_device(struct device *dev, struct scatterlist *sg,
 #define dma_map_sg(d, s, n, r) dma_map_sg_attrs(d, s, n, r, NULL)
 #define dma_unmap_sg(d, s, n, r) dma_unmap_sg_attrs(d, s, n, r, NULL)
 
+#ifdef CONFIG_HAS_DMA_P2P
+#define dma_map_peer_resource(d, p, e, o, s, r) \
+	dma_map_peer_resource_attrs(d, p, e, o, s, r, NULL)
+#define dma_unmap_peer_resource(d, a, s, r) \
+	dma_unmap_peer_resource_attrs(d, a, s, r, NULL)
+#endif
+
 extern int dma_common_mmap(struct device *dev, struct vm_area_struct *vma,
 			   void *cpu_addr, dma_addr_t dma_addr, size_t size);
 
diff --git a/include/linux/dma-mapping.h b/include/linux/dma-mapping.h
index ac07ff0..7b8fddc 100644
--- a/include/linux/dma-mapping.h
+++ b/include/linux/dma-mapping.h
@@ -34,6 +34,18 @@ struct dma_map_ops {
 	void (*unmap_page)(struct device *dev, dma_addr_t dma_handle,
 			   size_t size, enum dma_data_direction dir,
 			   struct dma_attrs *attrs);
+#ifdef CONFIG_HAS_DMA_P2P
+	dma_peer_addr_t (*map_peer_resource)(struct device *dev,
+					     struct device *peer,
+					     struct resource *res,
+					     unsigned long offset, size_t size,
+					     enum dma_data_direction dir,
+					     struct dma_attrs *attrs);
+	void (*unmap_peer_resource)(struct device *dev,
+				    dma_peer_addr_t dma_handle,
+				    size_t size, enum dma_data_direction dir,
+				    struct dma_attrs *attrs);
+#endif
 	/*
 	 * map_sg returns 0 on error and a value > 0 on success.
 	 * It should never return a value < 0.
-- 
2.5.0

Re: [PATCH v5 04/13] DMA-API: Introduce dma_(un)map_peer_resource

[Konrad Wilk]

> +#ifdef CONFIG_HAS_DMA_P2P
> +static inline dma_peer_addr_t dma_map_peer_resource_attrs(struct
> device *dev,
> +							  struct device *peer,
> +							  struct resource *res,
> +							  size_t offset,
> +							  size_t size,
> +							  enum dma_data_direction dir,
> +							  struct dma_attrs *attrs)
> +{
> +	struct dma_map_ops *ops = get_dma_ops(dev);
> +	dma_peer_addr_t addr;
> +
> +	BUG_ON(!valid_dma_direction(dir));
> +	BUG_ON(ops->map_peer_resource == NULL);
> +	addr = ops->map_peer_resource(dev, peer, res, offset, size, dir,
> +				      attrs);
> +	debug_dma_map_peer_resource(dev, peer, res, offset, size, dir,
> addr);
> +
> +	return addr;
> +

With those 'BUG_ON' you need to make sure that every dma_map_ops has
this implemented. That means the calgary_dma_ops, gart_dma_ops, swiotlb_dma_ops,
and xen_swiotlb_dma_ops MUST have something implemented.

Please keep in mind that on one can do 'iommu=soft swiotbl=force' on the
command line which will force the IOMMUs to be ignored and only the
SWIOTLB code will be used.

RE: [PATCH v5 04/13] DMA-API: Introduce dma_(un)map_peer_resource

[William Davis]

> > +#ifdef CONFIG_HAS_DMA_P2P
> > +static inline dma_peer_addr_t dma_map_peer_resource_attrs(struct
> > device *dev,
> > +							  struct device *peer,
> > +							  struct resource *res,
> > +							  size_t offset,
> > +							  size_t size,
> > +							  enum dma_data_direction dir,
> > +							  struct dma_attrs *attrs)
> > +{
> > +	struct dma_map_ops *ops = get_dma_ops(dev);
> > +	dma_peer_addr_t addr;
> > +
> > +	BUG_ON(!valid_dma_direction(dir));
> > +	BUG_ON(ops->map_peer_resource == NULL);
> > +	addr = ops->map_peer_resource(dev, peer, res, offset, size, dir,
> > +				      attrs);
> > +	debug_dma_map_peer_resource(dev, peer, res, offset, size, dir,
> > addr);
> > +
> > +	return addr;
> > +
> 
> With those 'BUG_ON' you need to make sure that every dma_map_ops has
> this implemented. That means the calgary_dma_ops, gart_dma_ops, swiotlb_dma_ops,
> and xen_swiotlb_dma_ops MUST have something implemented.
> 
> Please keep in mind that on one can do 'iommu=soft swiotbl=force' on the
> command line which will force the IOMMUs to be ignored and only the
> SWIOTLB code will be used.

Thanks for the feedback, Konrad. I will add implementations for those
dma_map_ops in v6.

Will

--
nvpublic