[PATCH v4 03/14] PCI/P2PDMA: Add PCI p2pmem dma mappings to adjust the bus offset

Logan Gunthorpe
2018-04-23T23:30:35Z

The DMA address used when mapping PCI P2P memory must be the PCI bus
address. Thus, introduce pci_p2pmem_[un]map_sg() to map the correct
addresses when using P2P memory.

For this, we assume that an SGL passed to these functions contain all
P2P memory or no P2P memory.

Signed-off-by: Logan Gunthorpe <logang-OTvnGxWRz7hWk0Htik3J/w@public.gmane.org>
---
drivers/pci/p2pdma.c | 51 ++++++++++++++++++++++++++++++++++++++++++++++
include/linux/memremap.h | 1 +
include/linux/pci-p2pdma.h | 13 ++++++++++++
3 files changed, 65 insertions(+)

diff --git a/drivers/pci/p2pdma.c b/drivers/pci/p2pdma.c
index 4daad6374869..ed9dce8552a2 100644
--- a/drivers/pci/p2pdma.c
+++ b/drivers/pci/p2pdma.c
@@ -190,6 +190,8 @@ int pci_p2pdma_add_resource(struct pci_dev *pdev, int bar, size_t size,
pgmap->res.flags = pci_resource_flags(pdev, bar);
pgmap->ref = &pdev->p2pdma->devmap_ref;
pgmap->type = MEMORY_DEVICE_PCI_P2PDMA;
+ pgmap->pci_p2pdma_bus_offset = pci_bus_address(pdev, bar) -
+ pci_resource_start(pdev, bar);

addr = devm_memremap_pages(&pdev->dev, pgmap);
if (IS_ERR(addr)) {
@@ -746,3 +748,52 @@ void pci_p2pmem_publish(struct pci_dev *pdev, bool publish)
pdev->p2pdma->p2pmem_published = publish;
}
EXPORT_SYMBOL_GPL(pci_p2pmem_publish);
+
+/**
+ * pci_p2pdma_map_sg - map a PCI peer-to-peer sg for DMA
+ * @dev: device doing the DMA request
+ * @sg: scatter list to map
+ * @nents: elements in the scatterlist
+ * @dir: DMA direction
+ *
+ * Returns the number of SG entries mapped
+ */
+int pci_p2pdma_map_sg(struct device *dev, struct scatterlist *sg, int nents,
+ enum dma_data_direction dir)
+{
+ struct dev_pagemap *pgmap;
+ struct scatterlist *s;
+ phys_addr_t paddr;
+ int i;
+
+ /*
+ * p2pdma mappings are not compatible with devices that use
+ * dma_virt_ops.
+ */
+ if (IS_ENABLED(CONFIG_DMA_VIRT_OPS) && dev->dma_ops == &dma_virt_ops)
+ return 0;
+
+ for_each_sg(sg, s, nents, i) {
+ pgmap = sg_page(s)->pgmap;
+ paddr = sg_phys(s);
+
+ s->dma_address = paddr - pgmap->pci_p2pdma_bus_offset;
+ sg_dma_len(s) = s->length;
+ }
+
+ return nents;
+}
+EXPORT_SYMBOL_GPL(pci_p2pdma_map_sg);
+
+/**
+ * pci_p2pdma_unmap_sg - unmap a PCI peer-to-peer sg for DMA
+ * @dev: device doing the DMA request
+ * @sg: scatter list to map
+ * @nents: elements in the scatterlist
+ * @dir: DMA direction
+ */
+void pci_p2pdma_unmap_sg(struct device *dev, struct scatterlist *sg, int nents,
+ enum dma_data_direction dir)
+{
+}
+EXPORT_SYMBOL_GPL(pci_p2pdma_unmap_sg);
diff --git a/include/linux/memremap.h b/include/linux/memremap.h
index 9e907c338a44..1660f64ce96f 100644
--- a/include/linux/memremap.h
+++ b/include/linux/memremap.h
@@ -125,6 +125,7 @@ struct dev_pagemap {
struct device *dev;
void *data;
enum memory_type type;
+ u64 pci_p2pdma_bus_offset;
};

#ifdef CONFIG_ZONE_DEVICE
diff --git a/include/linux/pci-p2pdma.h b/include/linux/pci-p2pdma.h
index 80e931cb1235..0cde88341eeb 100644
--- a/include/linux/pci-p2pdma.h
+++ b/include/linux/pci-p2pdma.h
@@ -35,6 +35,10 @@ struct scatterlist *pci_p2pmem_alloc_sgl(struct pci_dev *pdev,
unsigned int *nents, u32 length);
void pci_p2pmem_free_sgl(struct pci_dev *pdev, struct scatterlist *sgl);
void pci_p2pmem_publish(struct pci_dev *pdev, bool publish);
+int pci_p2pdma_map_sg(struct device *dev, struct scatterlist *sg, int nents,
+ enum dma_data_direction dir);
+void pci_p2pdma_unmap_sg(struct device *dev, struct scatterlist *sg, int nents,
+ enum dma_data_direction dir);
#else /* CONFIG_PCI_P2PDMA */
static inline int pci_p2pdma_add_resource(struct pci_dev *pdev, int bar,
size_t size, u64 offset)
@@ -96,5 +100,14 @@ static inline void pci_p2pmem_free_sgl(struct pci_dev *pdev,
static inline void pci_p2pmem_publish(struct pci_dev *pdev, bool publish)
{
}
+static inline int pci_p2pdma_map_sg(struct device *dev,
+ struct scatterlist *sg, int nents, enum dma_data_direction dir)
+{
+ return 0;
+}
+static inline void pci_p2pdma_unmap_sg(struct device *dev,
+ struct scatterlist *sg, int nents, enum dma_data_direction dir)
+{
+}
#endif /* CONFIG_PCI_P2PDMA */
#endif /* _LINUX_PCI_P2P_H */
--
2.11.0