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: Logan Gunthorpe <logang@deltatee.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Christoph Hellwig <hch@lst.de>
This commit is contained in:
Logan Gunthorpe 2022-07-08 10:50:56 -06:00 committed by Christoph Hellwig
parent 7c2645a2a3
commit f02ad36d4f
2 changed files with 44 additions and 7 deletions

View File

@ -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,

View File

@ -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);