Commit f02ad36d authored by Logan Gunthorpe's avatar Logan Gunthorpe Committed by Christoph Hellwig
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dma-direct: support PCI P2PDMA pages in dma-direct map_sg 



Add PCI P2PDMA support for dma_direct_map_sg() so that it can map
PCI P2PDMA pages directly without a hack in the callers. This allows
for heterogeneous SGLs that contain both P2PDMA and regular pages.

A P2PDMA page may have three possible outcomes when being mapped:
  1) If the data path between the two devices doesn't go through the
     root port, then it should be mapped with a PCI bus address
  2) If the data path goes through the host bridge, it should be mapped
     normally, as though it were a CPU physical address
  3) It is not possible for the two devices to communicate and thus
     the mapping operation should fail (and it will return -EREMOTEIO).

SGL segments that contain PCI bus addresses are marked with
sg_dma_mark_pci_p2pdma() and are ignored when unmapped.

P2PDMA mappings are also failed if swiotlb needs to be used on the
mapping.

Signed-off-by: default avatarLogan Gunthorpe <logang@deltatee.com>
Reviewed-by: default avatarChristoph Hellwig <hch@lst.de>
Signed-off-by: default avatarChristoph Hellwig <hch@lst.de>
parent 7c2645a2

kernel/dma/direct.c

+37 −6
Original line number Diff line number Diff line
@@ -454,29 +454,60 @@ void dma_direct_sync_sg_for_cpu(struct device *dev, 
		arch_sync_dma_for_cpu_all();

}



/*

 * Unmaps segments, except for ones marked as pci_p2pdma which do not

 * require any further action as they contain a bus address.

 */

void dma_direct_unmap_sg(struct device *dev, struct scatterlist *sgl,

		int nents, enum dma_data_direction dir, unsigned long attrs)

{

	struct scatterlist *sg;

	int i;



	for_each_sg(sgl, sg, nents, i)

		dma_direct_unmap_page(dev, sg->dma_address, sg_dma_len(sg), dir,

			     attrs);

	for_each_sg(sgl,  sg, nents, i) {

		if (sg_is_dma_bus_address(sg))

			sg_dma_unmark_bus_address(sg);

		else

			dma_direct_unmap_page(dev, sg->dma_address,

					      sg_dma_len(sg), dir, attrs);

	}

}

#endif



int dma_direct_map_sg(struct device *dev, struct scatterlist *sgl, int nents,

		enum dma_data_direction dir, unsigned long attrs)

{

	int i;

	struct pci_p2pdma_map_state p2pdma_state = {};

	enum pci_p2pdma_map_type map;

	struct scatterlist *sg;

	int i, ret;



	for_each_sg(sgl, sg, nents, i) {

		if (is_pci_p2pdma_page(sg_page(sg))) {

			map = pci_p2pdma_map_segment(&p2pdma_state, dev, sg);

			switch (map) {

			case PCI_P2PDMA_MAP_BUS_ADDR:

				continue;

			case PCI_P2PDMA_MAP_THRU_HOST_BRIDGE:

				/*

				 * Any P2P mapping that traverses the PCI

				 * host bridge must be mapped with CPU physical

				 * address and not PCI bus addresses. This is

				 * done with dma_direct_map_page() below.

				 */

				break;

			default:

				ret = -EREMOTEIO;

				goto out_unmap;

			}

		}



		sg->dma_address = dma_direct_map_page(dev, sg_page(sg),

				sg->offset, sg->length, dir, attrs);

		if (sg->dma_address == DMA_MAPPING_ERROR)

		if (sg->dma_address == DMA_MAPPING_ERROR) {

			ret = -EIO;

			goto out_unmap;

		}

		sg_dma_len(sg) = sg->length;

	}
@@ -484,7 +515,7 @@ int dma_direct_map_sg(struct device *dev, struct scatterlist *sgl, int nents, 


out_unmap:

	dma_direct_unmap_sg(dev, sgl, i, dir, attrs | DMA_ATTR_SKIP_CPU_SYNC);

	return -EIO;

	return ret;

}



dma_addr_t dma_direct_map_resource(struct device *dev, phys_addr_t paddr,

kernel/dma/direct.h

+7 −1
Original line number Diff line number Diff line
@@ -8,6 +8,7 @@ 
#define _KERNEL_DMA_DIRECT_H



#include <linux/dma-direct.h>

#include <linux/memremap.h>



int dma_direct_get_sgtable(struct device *dev, struct sg_table *sgt,

		void *cpu_addr, dma_addr_t dma_addr, size_t size,
@@ -87,10 +88,15 @@ static inline dma_addr_t dma_direct_map_page(struct device *dev, 
	phys_addr_t phys = page_to_phys(page) + offset;

	dma_addr_t dma_addr = phys_to_dma(dev, phys);



	if (is_swiotlb_force_bounce(dev))

	if (is_swiotlb_force_bounce(dev)) {

		if (is_pci_p2pdma_page(page))

			return DMA_MAPPING_ERROR;

		return swiotlb_map(dev, phys, size, dir, attrs);

	}



	if (unlikely(!dma_capable(dev, dma_addr, size, true))) {

		if (is_pci_p2pdma_page(page))

			return DMA_MAPPING_ERROR;

		if (is_swiotlb_active(dev))

			return swiotlb_map(dev, phys, size, dir, attrs);