Re: [PATCH v4 03/16] dma-debug: refactor to use physical addresses for page mapping

[Jason Gunthorpe]

On Tue, Aug 19, 2025 at 08:36:47PM +0300, Leon Romanovsky wrote:
> @@ -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 (!(attrs & DMA_ATTR_MMIO)) {
> +             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);
> +             }
>       }

Not anything to change in this series, but I was looking at what it
would take to someday remove the struct page here and it looks
reasonable.

diff --git a/kernel/dma/debug.c b/kernel/dma/debug.c
index 06e31fd216e38e..0d6dd3eb9860ac 100644
--- a/kernel/dma/debug.c
+++ b/kernel/dma/debug.c
@@ -1051,28 +1051,28 @@ 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 {
                /* Stack is vmalloced. */
+               unsigned long pfn = phys >> PAGE_SHIFT;
                int i;
 
                for (i = 0; i < stack_vm_area->nr_pages; i++) {
-                       if (page != stack_vm_area->pages[i])
+                       if (pfn != 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;
                }
@@ -1225,16 +1225,10 @@ void debug_dma_map_phys(struct device *dev, phys_addr_t 
phys, size_t size,
        entry->map_err_type = MAP_ERR_NOT_CHECKED;
 
        if (!(attrs & DMA_ATTR_MMIO)) {
-               struct page *page = phys_to_page(phys);
-               size_t offset = offset_in_page(page);
+               check_for_stack(dev, phys);
 
-               check_for_stack(dev, page, offset);
-
-               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);