[PATCH v6 03/16] dma-debug: refactor to use physical addresses for page mapping

Leon Romanovsky
2025-09-09T13:28:23Z

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.

Reviewed-by: Jason Gunthorpe <jgg@nvidia.com>
Signed-off-by: Leon Romanovsky <leonro@nvidia.com>
---
Documentation/core-api/dma-api.rst | 4 +--
include/linux/page-flags.h | 1 +
kernel/dma/debug.c | 39 +++++++++++++++---------------
kernel/dma/debug.h | 16 ++++++------
kernel/dma/mapping.c | 10 ++++----
5 files changed, 35 insertions(+), 35 deletions(-)

diff --git a/Documentation/core-api/dma-api.rst b/Documentation/core-api/dma-api.rst
index 3087bea715ed2..ca75b35416792 100644
--- a/Documentation/core-api/dma-api.rst
+++ b/Documentation/core-api/dma-api.rst
@@ -761,7 +761,7 @@ 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
@@ -855,7 +855,7 @@ 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/include/linux/page-flags.h b/include/linux/page-flags.h
index 8d3fa3a91ce47..dfbc4ba86bba2 100644
--- a/include/linux/page-flags.h
+++ b/include/linux/page-flags.h
@@ -614,6 +614,7 @@ FOLIO_FLAG(dropbehind, FOLIO_HEAD_PAGE)
* available at this point.
*/
#define PageHighMem(__p) is_highmem_idx(page_zonenum(__p))
+#define PhysHighMem(__p) (PageHighMem(phys_to_page(__p)))
#define folio_test_highmem(__f) is_highmem_idx(folio_zonenum(__f))
#else
PAGEFLAG_FALSE(HighMem, highmem)
diff --git a/kernel/dma/debug.c b/kernel/dma/debug.c
index b82399437db03..b275db9ca6a03 100644
--- a/kernel/dma/debug.c
+++ b/kernel/dma/debug.c
@@ -40,6 +40,7 @@ enum {
dma_debug_coherent,
dma_debug_resource,
dma_debug_noncoherent,
+ dma_debug_phy,
};

enum map_err_types {
@@ -143,6 +144,7 @@ static const char *type2name[] = {
[dma_debug_coherent] = "coherent",
[dma_debug_resource] = "resource",
[dma_debug_noncoherent] = "noncoherent",
+ [dma_debug_phy] = "phy",
};

static const char *dir2name[] = {
@@ -1054,17 +1056,16 @@ static void check_unmap(struct dma_debug_entry *ref)
dma_entry_free(entry);
}

-static void check_for_stack(struct device *dev,
- struct page *page, size_t offset)
+static void check_for_stack(struct device *dev, phys_addr_t phys)
{
void *addr;
struct vm_struct *stack_vm_area = task_stack_vm_area(current);

if (!stack_vm_area) {
/* Stack is direct-mapped. */
- if (PageHighMem(page))
+ if (PhysHighMem(phys))
return;
- addr = page_address(page) + offset;
+ addr = phys_to_virt(phys);
if (object_is_on_stack(addr))
err_printk(dev, NULL, "device driver maps memory from stack [addr=%p]\n", addr);
} else {
@@ -1072,10 +1073,12 @@ static void check_for_stack(struct device *dev,
int i;

for (i = 0; i < stack_vm_area->nr_pages; i++) {
- if (page != stack_vm_area->pages[i])
+ if (__phys_to_pfn(phys) !=
+ page_to_pfn(stack_vm_area->pages[i]))
continue;

- addr = (u8 *)current->stack + i * PAGE_SIZE + offset;
+ addr = (u8 *)current->stack + i * PAGE_SIZE +
+ (phys % PAGE_SIZE);
err_printk(dev, NULL, "device driver maps memory from stack [probable addr=%p]\n", addr);
break;
}
@@ -1204,9 +1207,8 @@ 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;

@@ -1221,19 +1223,18 @@ 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 (!(attrs & DMA_ATTR_MMIO)) {
+ check_for_stack(dev, phys);

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

add_dma_entry(entry, attrs);
@@ -1277,11 +1278,11 @@ 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,
@@ -1305,7 +1306,7 @@ void debug_dma_map_sg(struct device *dev, struct scatterlist *sg,
return;

for_each_sg(sg, s, nents, i) {
- check_for_stack(dev, sg_page(s), s->offset);
+ check_for_stack(dev, sg_phys(s));
if (!PageHighMem(sg_page(s)))
check_for_illegal_area(dev, sg_virt(s), s->length);
}
diff --git a/kernel/dma/debug.h b/kernel/dma/debug.h
index 48757ca13f314..bedae973e725d 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,
@@ -62,14 +61,13 @@ extern void debug_dma_free_pages(struct device *dev, struct page *page,
size_t size, int direction,
dma_addr_t dma_addr);
#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 56de28a3b1799..0b7e16c69bf18 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);

--
2.51.0