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.
The DMA_ATTR_P2PDMA flag is added to allow callers to indicate support
for P2PDMA pages. In order for a caller to support P2PDMA pages they
must ensure no segment is greater than 2GB such that the high bit
of the dma length can be used as a flag to indicate a P2PDMA segment.
Such code must then ensure to use sg_dma_p2pdma_len() instead of
sg_dma_len() to filter out the flag.
Signed-off-by: Logan Gunthorpe <logang@xxxxxxxxxxxx>
---
include/linux/dma-mapping.h | 11 +++++++++++
kernel/dma/direct.c | 33 +++++++++++++++++++++++++++++++--
2 files changed, 42 insertions(+), 2 deletions(-)
diff --git a/include/linux/dma-mapping.h b/include/linux/dma-mapping.h
index 956151052d45..8d028e15b531 100644
--- a/include/linux/dma-mapping.h
+++ b/include/linux/dma-mapping.h
@@ -61,6 +61,17 @@
*/
#define DMA_ATTR_PRIVILEGED (1UL << 9)
+/*
+ * DMA_ATTR_P2PDMA: specifies that dma_map_sg() may return p2pdma
+ * bus addresses. Code that specifies this must ensure to
+ * use sg_dma_p2pdma_len() instead of sg_dma_len() as the high
+ * bit of the length will indicate a P2PDMA bus address.
+ *
+ * If this attribute is not set and P2PDMA pages are encountered,
+ * dma_map_sg() will return an error.
+ */
+#define DMA_ATTR_P2PDMA (1UL << 10)
+
/*
* A dma_addr_t can hold any valid DMA or bus address for the platform. It can
* be given to a device to use as a DMA source or target. It is specific to a
diff --git a/kernel/dma/direct.c b/kernel/dma/direct.c
index 06c111544f61..2fcb31789436 100644
--- a/kernel/dma/direct.c
+++ b/kernel/dma/direct.c
@@ -13,6 +13,7 @@
#include <linux/vmalloc.h>
#include <linux/set_memory.h>
#include <linux/slab.h>
+#include <linux/pci-p2pdma.h>
#include "direct.h"
/*
@@ -387,19 +388,47 @@ void dma_direct_unmap_sg(struct device *dev, struct scatterlist *sgl,
struct scatterlist *sg;
int i;
- for_each_sg(sgl, sg, nents, i)
+ for_each_sg(sgl, sg, nents, i) {
+ if (attrs & DMA_ATTR_P2PDMA && sg_dma_is_p2pdma(sg)) {
+ sg_dma_len(sg) &= ~SG_P2PDMA_FLAG;
+ continue;
+ }
+
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 dev_pagemap *pgmap = NULL;
+ int i, map = -1;
struct scatterlist *sg;
+ u64 bus_off;
for_each_sg(sgl, sg, nents, i) {
+ if (is_pci_p2pdma_page(sg_page(sg))) {
+ if (sg_page(sg)->pgmap != pgmap) {
+ pgmap = sg_page(sg)->pgmap;
+ map = pci_p2pdma_should_map_bus(dev, pgmap);
+ bus_off = pci_p2pdma_bus_offset(sg_page(sg));
+ }
+
+ if (map < 0 || !(attrs & DMA_ATTR_P2PDMA)) {
+ sg->dma_address = DMA_MAPPING_ERROR;
+ goto out_unmap;
+ }
+
+ if (map) {
+ sg->dma_address = sg_phys(sg) + sg->offset -
+ bus_off;
+ sg_dma_len(sg) = sg->length | SG_P2PDMA_FLAG;
+ continue;
+ }
+ }
+
sg->dma_address = dma_direct_map_page(dev, sg_page(sg),
sg->offset, sg->length, dir, attrs);
if (sg->dma_address == DMA_MAPPING_ERROR)
--
2.20.1
