[PATCH 1/8] dma-debug: refactor to use physical addresses for page mapping

Leon Romanovsky
2025-06-25T13:19:27Z

From: Leon Romanovsky <leonro@nvidia.com>

Convert the DMA debug infrastructure from page-based to physical address-based
mapping as a preparation to rely on physical address for DMA mapping routines.

The refactoring renames debug_dma_map_page() to debug_dma_map_phys() and
changes its signature to accept a phys_addr_t parameter instead of struct page
and offset. Similarly, debug_dma_unmap_page() becomes debug_dma_unmap_phys().
A new dma_debug_phy type is introduced to distinguish physical address mappings
from other debug entry types. All callers throughout the codebase are updated
to pass physical addresses directly, eliminating the need for page-to-physical
conversion in the debug layer.

This refactoring eliminates the need to convert between page pointers and
physical addresses in the debug layer, making the code more efficient and
consistent with the DMA mapping API's physical address focus.

Signed-off-by: Leon Romanovsky <leonro@nvidia.com>
---
Documentation/core-api/dma-api.rst | 4 ++--
kernel/dma/debug.c | 28 +++++++++++++++++-----------
kernel/dma/debug.h | 16 +++++++---------
kernel/dma/mapping.c | 15 ++++++++-------
4 files changed, 34 insertions(+), 29 deletions(-)

diff --git a/Documentation/core-api/dma-api.rst b/Documentation/core-api/dma-api.rst
index 2ad08517e626..7491ee85ab25 100644
--- a/Documentation/core-api/dma-api.rst
+++ b/Documentation/core-api/dma-api.rst
@@ -816,7 +816,7 @@ example warning message may look like this::
[<ffffffff80235177>] find_busiest_group+0x207/0x8a0
[<ffffffff8064784f>] _spin_lock_irqsave+0x1f/0x50
[<ffffffff803c7ea3>] check_unmap+0x203/0x490
- [<ffffffff803c8259>] debug_dma_unmap_page+0x49/0x50
+ [<ffffffff803c8259>] debug_dma_unmap_phys+0x49/0x50
[<ffffffff80485f26>] nv_tx_done_optimized+0xc6/0x2c0
[<ffffffff80486c13>] nv_nic_irq_optimized+0x73/0x2b0
[<ffffffff8026df84>] handle_IRQ_event+0x34/0x70
@@ -910,7 +910,7 @@ that a driver may be leaking mappings.
dma-debug interface debug_dma_mapping_error() to debug drivers that fail
to check DMA mapping errors on addresses returned by dma_map_single() and
dma_map_page() interfaces. This interface clears a flag set by
-debug_dma_map_page() to indicate that dma_mapping_error() has been called by
+debug_dma_map_phys() to indicate that dma_mapping_error() has been called by
the driver. When driver does unmap, debug_dma_unmap() checks the flag and if
this flag is still set, prints warning message that includes call trace that
leads up to the unmap. This interface can be called from dma_mapping_error()
diff --git a/kernel/dma/debug.c b/kernel/dma/debug.c
index e43c6de2bce4..517dc58329e0 100644
--- a/kernel/dma/debug.c
+++ b/kernel/dma/debug.c
@@ -39,6 +39,7 @@ enum {
dma_debug_sg,
dma_debug_coherent,
dma_debug_resource,
+ dma_debug_phy,
};

enum map_err_types {
@@ -141,6 +142,7 @@ static const char *type2name[] = {
[dma_debug_sg] = "scatter-gather",
[dma_debug_coherent] = "coherent",
[dma_debug_resource] = "resource",
+ [dma_debug_phy] = "phy",
};

static const char *dir2name[] = {
@@ -1201,9 +1203,8 @@ void debug_dma_map_single(struct device *dev, const void *addr,
}
EXPORT_SYMBOL(debug_dma_map_single);

-void debug_dma_map_page(struct device *dev, struct page *page, size_t offset,
- size_t size, int direction, dma_addr_t dma_addr,
- unsigned long attrs)
+void debug_dma_map_phys(struct device *dev, phys_addr_t phys, size_t size,
+ int direction, dma_addr_t dma_addr, unsigned long attrs)
{
struct dma_debug_entry *entry;

@@ -1218,19 +1219,24 @@ void debug_dma_map_page(struct device *dev, struct page *page, size_t offset,
return;

entry->dev = dev;
- entry->type = dma_debug_single;
- entry->paddr = page_to_phys(page) + offset;
+ entry->type = dma_debug_phy;
+ entry->paddr = phys;
entry->dev_addr = dma_addr;
entry->size = size;
entry->direction = direction;
entry->map_err_type = MAP_ERR_NOT_CHECKED;

- check_for_stack(dev, page, offset);
+ if (pfn_valid(PHYS_PFN(phys))) {
+ struct page *page = phys_to_page(phys);
+ size_t offset = offset_in_page(page);

- if (!PageHighMem(page)) {
- void *addr = page_address(page) + offset;
+ check_for_stack(dev, page, offset);

- check_for_illegal_area(dev, addr, size);
+ if (!PageHighMem(page)) {
+ void *addr = page_address(page) + offset;
+
+ check_for_illegal_area(dev, addr, size);
+ }
}

add_dma_entry(entry, attrs);
@@ -1274,11 +1280,11 @@ void debug_dma_mapping_error(struct device *dev, dma_addr_t dma_addr)
}
EXPORT_SYMBOL(debug_dma_mapping_error);

-void debug_dma_unmap_page(struct device *dev, dma_addr_t dma_addr,
+void debug_dma_unmap_phys(struct device *dev, dma_addr_t dma_addr,
size_t size, int direction)
{
struct dma_debug_entry ref = {
- .type = dma_debug_single,
+ .type = dma_debug_phy,
.dev = dev,
.dev_addr = dma_addr,
.size = size,
diff --git a/kernel/dma/debug.h b/kernel/dma/debug.h
index f525197d3cae..76adb42bffd5 100644
--- a/kernel/dma/debug.h
+++ b/kernel/dma/debug.h
@@ -9,12 +9,11 @@
#define _KERNEL_DMA_DEBUG_H

#ifdef CONFIG_DMA_API_DEBUG
-extern void debug_dma_map_page(struct device *dev, struct page *page,
- size_t offset, size_t size,
- int direction, dma_addr_t dma_addr,
+extern void debug_dma_map_phys(struct device *dev, phys_addr_t phys,
+ size_t size, int direction, dma_addr_t dma_addr,
unsigned long attrs);

-extern void debug_dma_unmap_page(struct device *dev, dma_addr_t addr,
+extern void debug_dma_unmap_phys(struct device *dev, dma_addr_t addr,
size_t size, int direction);

extern void debug_dma_map_sg(struct device *dev, struct scatterlist *sg,
@@ -55,14 +54,13 @@ extern void debug_dma_sync_sg_for_device(struct device *dev,
struct scatterlist *sg,
int nelems, int direction);
#else /* CONFIG_DMA_API_DEBUG */
-static inline void debug_dma_map_page(struct device *dev, struct page *page,
- size_t offset, size_t size,
- int direction, dma_addr_t dma_addr,
- unsigned long attrs)
+static inline void debug_dma_map_phys(struct device *dev, phys_addr_t phys,
+ size_t size, int direction,
+ dma_addr_t dma_addr, unsigned long attrs)
{
}

-static inline void debug_dma_unmap_page(struct device *dev, dma_addr_t addr,
+static inline void debug_dma_unmap_phys(struct device *dev, dma_addr_t addr,
size_t size, int direction)
{
}
diff --git a/kernel/dma/mapping.c b/kernel/dma/mapping.c
index 107e4a4d251d..4c1dfbabb8ae 100644
--- a/kernel/dma/mapping.c
+++ b/kernel/dma/mapping.c
@@ -157,6 +157,7 @@ dma_addr_t dma_map_page_attrs(struct device *dev, struct page *page,
unsigned long attrs)
{
const struct dma_map_ops *ops = get_dma_ops(dev);
+ phys_addr_t phys = page_to_phys(page) + offset;
dma_addr_t addr;

BUG_ON(!valid_dma_direction(dir));
@@ -165,16 +166,15 @@ 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, page_to_phys(page) + offset + size))
+ arch_dma_map_page_direct(dev, phys + size))
addr = dma_direct_map_page(dev, page, offset, size, dir, attrs);
else if (use_dma_iommu(dev))
addr = iommu_dma_map_page(dev, page, offset, size, dir, attrs);
else
addr = ops->map_page(dev, page, offset, size, dir, attrs);
kmsan_handle_dma(page, offset, size, dir);
- trace_dma_map_page(dev, page_to_phys(page) + offset, addr, size, dir,
- attrs);
- debug_dma_map_page(dev, page, offset, size, dir, addr, attrs);
+ trace_dma_map_page(dev, phys, addr, size, dir, attrs);
+ debug_dma_map_phys(dev, phys, size, dir, addr, attrs);

return addr;
}
@@ -194,7 +194,7 @@ void dma_unmap_page_attrs(struct device *dev, dma_addr_t addr, size_t size,
else
ops->unmap_page(dev, addr, size, dir, attrs);
trace_dma_unmap_page(dev, addr, size, dir, attrs);
- debug_dma_unmap_page(dev, addr, size, dir);
+ debug_dma_unmap_phys(dev, addr, size, dir);
}
EXPORT_SYMBOL(dma_unmap_page_attrs);

@@ -712,7 +712,8 @@ struct page *dma_alloc_pages(struct device *dev, size_t size,
if (page) {
trace_dma_alloc_pages(dev, page_to_virt(page), *dma_handle,
size, dir, gfp, 0);
- debug_dma_map_page(dev, page, 0, size, dir, *dma_handle, 0);
+ debug_dma_map_phys(dev, page_to_phys(page), size, dir,
+ *dma_handle, 0);
} else {
trace_dma_alloc_pages(dev, NULL, 0, size, dir, gfp, 0);
}
@@ -738,7 +739,7 @@ void dma_free_pages(struct device *dev, size_t size, struct page *page,
dma_addr_t dma_handle, enum dma_data_direction dir)
{
trace_dma_free_pages(dev, page_to_virt(page), dma_handle, size, dir, 0);
- debug_dma_unmap_page(dev, dma_handle, size, dir);
+ debug_dma_unmap_phys(dev, dma_handle, size, dir);
__dma_free_pages(dev, size, page, dma_handle, dir);
}
EXPORT_SYMBOL_GPL(dma_free_pages);
--
2.49.0