[PATCH v6 07/16] dma-mapping: convert dma_direct_*map_page to be phys_addr_t based

Leon Romanovsky
2025-09-09T13:28:39Z

Convert the DMA direct mapping functions to accept physical addresses
directly instead of page+offset parameters. The functions were already
operating on physical addresses internally, so this change eliminates
the redundant page-to-physical conversion at the API boundary.

The functions dma_direct_map_page() and dma_direct_unmap_page() are
renamed to dma_direct_map_phys() and dma_direct_unmap_phys() respectively,
with their calling convention changed from (struct page *page,
unsigned long offset) to (phys_addr_t phys).

Architecture-specific functions arch_dma_map_page_direct() and
arch_dma_unmap_page_direct() are similarly renamed to
arch_dma_map_phys_direct() and arch_dma_unmap_phys_direct().

The is_pci_p2pdma_page() checks are replaced with DMA_ATTR_MMIO checks
to allow integration with dma_direct_map_resource and dma_direct_map_phys()
is extended to support MMIO path either.

Reviewed-by: Jason Gunthorpe <jgg@nvidia.com>
Signed-off-by: Leon Romanovsky <leonro@nvidia.com>
---
arch/powerpc/kernel/dma-iommu.c | 4 +--
include/linux/dma-map-ops.h | 8 ++---
kernel/dma/direct.c | 6 ++--
kernel/dma/direct.h | 57 +++++++++++++++++++++------------
kernel/dma/mapping.c | 8 ++---
5 files changed, 49 insertions(+), 34 deletions(-)

diff --git a/arch/powerpc/kernel/dma-iommu.c b/arch/powerpc/kernel/dma-iommu.c
index 4d64a5db50f38..0359ab72cd3ba 100644
--- a/arch/powerpc/kernel/dma-iommu.c
+++ b/arch/powerpc/kernel/dma-iommu.c
@@ -14,7 +14,7 @@
#define can_map_direct(dev, addr) \
((dev)->bus_dma_limit >= phys_to_dma((dev), (addr)))

-bool arch_dma_map_page_direct(struct device *dev, phys_addr_t addr)
+bool arch_dma_map_phys_direct(struct device *dev, phys_addr_t addr)
{
if (likely(!dev->bus_dma_limit))
return false;
@@ -24,7 +24,7 @@ bool arch_dma_map_page_direct(struct device *dev, phys_addr_t addr)

#define is_direct_handle(dev, h) ((h) >= (dev)->archdata.dma_offset)

-bool arch_dma_unmap_page_direct(struct device *dev, dma_addr_t dma_handle)
+bool arch_dma_unmap_phys_direct(struct device *dev, dma_addr_t dma_handle)
{
if (likely(!dev->bus_dma_limit))
return false;
diff --git a/include/linux/dma-map-ops.h b/include/linux/dma-map-ops.h
index f48e5fb88bd5d..71f5b30254159 100644
--- a/include/linux/dma-map-ops.h
+++ b/include/linux/dma-map-ops.h
@@ -392,15 +392,15 @@ void *arch_dma_set_uncached(void *addr, size_t size);
void arch_dma_clear_uncached(void *addr, size_t size);

#ifdef CONFIG_ARCH_HAS_DMA_MAP_DIRECT
-bool arch_dma_map_page_direct(struct device *dev, phys_addr_t addr);
-bool arch_dma_unmap_page_direct(struct device *dev, dma_addr_t dma_handle);
+bool arch_dma_map_phys_direct(struct device *dev, phys_addr_t addr);
+bool arch_dma_unmap_phys_direct(struct device *dev, dma_addr_t dma_handle);
bool arch_dma_map_sg_direct(struct device *dev, struct scatterlist *sg,
int nents);
bool arch_dma_unmap_sg_direct(struct device *dev, struct scatterlist *sg,
int nents);
#else
-#define arch_dma_map_page_direct(d, a) (false)
-#define arch_dma_unmap_page_direct(d, a) (false)
+#define arch_dma_map_phys_direct(d, a) (false)
+#define arch_dma_unmap_phys_direct(d, a) (false)
#define arch_dma_map_sg_direct(d, s, n) (false)
#define arch_dma_unmap_sg_direct(d, s, n) (false)
#endif
diff --git a/kernel/dma/direct.c b/kernel/dma/direct.c
index 24c359d9c8799..fa75e30700730 100644
--- a/kernel/dma/direct.c
+++ b/kernel/dma/direct.c
@@ -453,7 +453,7 @@ void dma_direct_unmap_sg(struct device *dev, struct scatterlist *sgl,
if (sg_dma_is_bus_address(sg))
sg_dma_unmark_bus_address(sg);
else
- dma_direct_unmap_page(dev, sg->dma_address,
+ dma_direct_unmap_phys(dev, sg->dma_address,
sg_dma_len(sg), dir, attrs);
}
}
@@ -476,8 +476,8 @@ int dma_direct_map_sg(struct device *dev, struct scatterlist *sgl, int nents,
*/
break;
case PCI_P2PDMA_MAP_NONE:
- sg->dma_address = dma_direct_map_page(dev, sg_page(sg),
- sg->offset, sg->length, dir, attrs);
+ sg->dma_address = dma_direct_map_phys(dev, sg_phys(sg),
+ sg->length, dir, attrs);
if (sg->dma_address == DMA_MAPPING_ERROR) {
ret = -EIO;
goto out_unmap;
diff --git a/kernel/dma/direct.h b/kernel/dma/direct.h
index d2c0b7e632fc0..da2fadf45bcd6 100644
--- a/kernel/dma/direct.h
+++ b/kernel/dma/direct.h
@@ -80,42 +80,57 @@ static inline void dma_direct_sync_single_for_cpu(struct device *dev,
arch_dma_mark_clean(paddr, size);
}

-static inline dma_addr_t dma_direct_map_page(struct device *dev,
- struct page *page, unsigned long offset, size_t size,
- enum dma_data_direction dir, unsigned long attrs)
+static inline dma_addr_t dma_direct_map_phys(struct device *dev,
+ phys_addr_t phys, size_t size, enum dma_data_direction dir,
+ unsigned long attrs)
{
- phys_addr_t phys = page_to_phys(page) + offset;
- dma_addr_t dma_addr = phys_to_dma(dev, phys);
+ dma_addr_t dma_addr;

if (is_swiotlb_force_bounce(dev)) {
- if (is_pci_p2pdma_page(page))
- return DMA_MAPPING_ERROR;
+ if (attrs & DMA_ATTR_MMIO)
+ goto err_overflow;
+
return swiotlb_map(dev, phys, size, dir, attrs);
}

- if (unlikely(!dma_capable(dev, dma_addr, size, true)) ||
- dma_kmalloc_needs_bounce(dev, size, dir)) {
- if (is_pci_p2pdma_page(page))
- return DMA_MAPPING_ERROR;
- if (is_swiotlb_active(dev))
- return swiotlb_map(dev, phys, size, dir, attrs);
-
- dev_WARN_ONCE(dev, 1,
- "DMA addr %pad+%zu overflow (mask %llx, bus limit %llx).\n",
- &dma_addr, size, *dev->dma_mask, dev->bus_dma_limit);
- return DMA_MAPPING_ERROR;
+ if (attrs & DMA_ATTR_MMIO) {
+ dma_addr = phys;
+ if (unlikely(!dma_capable(dev, dma_addr, size, false)))
+ goto err_overflow;
+ } else {
+ dma_addr = phys_to_dma(dev, phys);
+ if (unlikely(!dma_capable(dev, dma_addr, size, true)) ||
+ dma_kmalloc_needs_bounce(dev, size, dir)) {
+ if (is_swiotlb_active(dev))
+ return swiotlb_map(dev, phys, size, dir, attrs);
+
+ goto err_overflow;
+ }
}

- if (!dev_is_dma_coherent(dev) && !(attrs & DMA_ATTR_SKIP_CPU_SYNC))
+ if (!dev_is_dma_coherent(dev) &&
+ !(attrs & (DMA_ATTR_SKIP_CPU_SYNC | DMA_ATTR_MMIO)))
arch_sync_dma_for_device(phys, size, dir);
return dma_addr;
+
+err_overflow:
+ dev_WARN_ONCE(
+ dev, 1,
+ "DMA addr %pad+%zu overflow (mask %llx, bus limit %llx).\n",
+ &dma_addr, size, *dev->dma_mask, dev->bus_dma_limit);
+ return DMA_MAPPING_ERROR;
}

-static inline void dma_direct_unmap_page(struct device *dev, dma_addr_t addr,
+static inline void dma_direct_unmap_phys(struct device *dev, dma_addr_t addr,
size_t size, enum dma_data_direction dir, unsigned long attrs)
{
- phys_addr_t phys = dma_to_phys(dev, addr);
+ phys_addr_t phys;
+
+ if (attrs & DMA_ATTR_MMIO)
+ /* nothing to do: uncached and no swiotlb */
+ return;

+ phys = dma_to_phys(dev, addr);
if (!(attrs & DMA_ATTR_SKIP_CPU_SYNC))
dma_direct_sync_single_for_cpu(dev, addr, size, dir);

diff --git a/kernel/dma/mapping.c b/kernel/dma/mapping.c
index 90ad728205b93..3ac7d15e095f9 100644
--- a/kernel/dma/mapping.c
+++ b/kernel/dma/mapping.c
@@ -166,8 +166,8 @@ dma_addr_t dma_map_page_attrs(struct device *dev, struct page *page,
return DMA_MAPPING_ERROR;

if (dma_map_direct(dev, ops) ||
- arch_dma_map_page_direct(dev, phys + size))
- addr = dma_direct_map_page(dev, page, offset, size, dir, attrs);
+ arch_dma_map_phys_direct(dev, phys + size))
+ addr = dma_direct_map_phys(dev, phys, size, dir, attrs);
else if (use_dma_iommu(dev))
addr = iommu_dma_map_phys(dev, phys, size, dir, attrs);
else
@@ -187,8 +187,8 @@ void dma_unmap_page_attrs(struct device *dev, dma_addr_t addr, size_t size,

BUG_ON(!valid_dma_direction(dir));
if (dma_map_direct(dev, ops) ||
- arch_dma_unmap_page_direct(dev, addr + size))
- dma_direct_unmap_page(dev, addr, size, dir, attrs);
+ arch_dma_unmap_phys_direct(dev, addr + size))
+ dma_direct_unmap_phys(dev, addr, size, dir, attrs);
else if (use_dma_iommu(dev))
iommu_dma_unmap_phys(dev, addr, size, dir, attrs);
else
--
2.51.0