| Message ID | alpine.DEB.2.02.1411111644490.26318@kaball.uk.xensource.com |
|---|---|
| State | New |
| Headers | show |
On Mon, 17 Nov 2014, Stefano Stabellini wrote: > Hi all, > I am writing this email to ask for your advice. > > On architectures where dma addresses are different from physical > addresses, it can be difficult to retrieve the physical address of a > page from its dma address. > > Specifically this is the case for Xen on arm and arm64 but I think that > other architectures might have the same issue. > > Knowing the physical address is necessary to be able to issue any > required cache maintenance operations when unmap_page, > sync_single_for_cpu and sync_single_for_device are called. > > Adding a struct page* parameter to unmap_page, sync_single_for_cpu and > sync_single_for_device would make Linux dma handling on Xen on arm and > arm64 much easier and quicker. > > I think that other drivers have similar problems, such as the Intel > IOMMU driver having to call find_iova and walking down an rbtree to get > the physical address in its implementation of unmap_page. > > Callers have the struct page* in their hands already from the previous > map_page call so it shouldn't be an issue for them. A problem does > exist however: there are about 280 callers of dma_unmap_page and > pci_unmap_page. We have even more callers of the dma_sync_single_for_* > functions. > > > > Is such a change even conceivable? How would one go about it? > > I think that Xen would not be the only one to gain from it, but I would > like to have a confirmation from others: given the magnitude of the > changes involved I would actually prefer to avoid them unless multiple > drivers/archs/subsystems could really benefit from them. Given the lack of interest from the community, I am going to drop this idea. > Cheers, > > Stefano > > > diff --git a/include/linux/dma-mapping.h b/include/linux/dma-mapping.h > index d5d3881..158a765 100644 > --- a/include/linux/dma-mapping.h > +++ b/include/linux/dma-mapping.h > @@ -31,8 +31,9 @@ struct dma_map_ops { > unsigned long offset, size_t size, > enum dma_data_direction dir, > struct dma_attrs *attrs); > - void (*unmap_page)(struct device *dev, dma_addr_t dma_handle, > - size_t size, enum dma_data_direction dir, > + void (*unmap_page)(struct device *dev, struct page *page, > + dma_addr_t dma_handle, size_t size, > + enum dma_data_direction dir, > struct dma_attrs *attrs); > int (*map_sg)(struct device *dev, struct scatterlist *sg, > int nents, enum dma_data_direction dir, > @@ -41,10 +42,10 @@ struct dma_map_ops { > struct scatterlist *sg, int nents, > enum dma_data_direction dir, > struct dma_attrs *attrs); > - void (*sync_single_for_cpu)(struct device *dev, > + void (*sync_single_for_cpu)(struct device *dev, struct page *page, > dma_addr_t dma_handle, size_t size, > enum dma_data_direction dir); > - void (*sync_single_for_device)(struct device *dev, > + void (*sync_single_for_device)(struct device *dev, struct page *page, > dma_addr_t dma_handle, size_t size, > enum dma_data_direction dir); > void (*sync_sg_for_cpu)(struct device *dev, > -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
diff --git a/include/linux/dma-mapping.h b/include/linux/dma-mapping.h index d5d3881..158a765 100644 --- a/include/linux/dma-mapping.h +++ b/include/linux/dma-mapping.h @@ -31,8 +31,9 @@ struct dma_map_ops { unsigned long offset, size_t size, enum dma_data_direction dir, struct dma_attrs *attrs); - void (*unmap_page)(struct device *dev, dma_addr_t dma_handle, - size_t size, enum dma_data_direction dir, + void (*unmap_page)(struct device *dev, struct page *page, + dma_addr_t dma_handle, size_t size, + enum dma_data_direction dir, struct dma_attrs *attrs); int (*map_sg)(struct device *dev, struct scatterlist *sg, int nents, enum dma_data_direction dir, @@ -41,10 +42,10 @@ struct dma_map_ops { struct scatterlist *sg, int nents, enum dma_data_direction dir, struct dma_attrs *attrs); - void (*sync_single_for_cpu)(struct device *dev, + void (*sync_single_for_cpu)(struct device *dev, struct page *page, dma_addr_t dma_handle, size_t size, enum dma_data_direction dir); - void (*sync_single_for_device)(struct device *dev, + void (*sync_single_for_device)(struct device *dev, struct page *page, dma_addr_t dma_handle, size_t size, enum dma_data_direction dir); void (*sync_sg_for_cpu)(struct device *dev,