dma-mapping: move dma_map_resource() sanity check into debug code

dma_map_resource() uses pfn_valid() to ensure the range is not RAM.
However, pfn_valid() only checks for availability of the memory map for
a PFN but it does not ensure that the PFN is actually backed by RAM. On
ARM64 with SPARSEMEM (128MB section granularity), MMIO addresses that
share a section with RAM will falsely trigger the WARN_ON_ONCE and cause
dma_map_resource() to return DMA_MAPPING_ERROR.

This causes a WARNING on Raspberry Pi 4 during spi_bcm2835 probe because
the SPI FIFO register (0xfe204004) falls in the same sparsemem section
as the end of RAM (0xf8000000-0xfbffffff), both in section 31
(0xf8000000-0xffffffff).

Move the sanity check from dma_map_resource() into debug_dma_map_phys()
and replace the unreliable pfn_valid() with pfn_valid() &&
!PageReserved(), which correctly identifies actual usable RAM without
false positives for MMIO regions that happen to have struct pages.

Since dma_map_resource() is dma_map_phys(DMA_ATTR_MMIO), the check
applies equally to both APIs. Any non-reserved page represents kernel
memory to a sufficient degree that using DMA_ATTR_MMIO on it is almost
certainly wrong and risks breaking coherency on non-coherent platforms.
ZONE_DEVICE pages used for PCI P2P DMA (MEMORY_DEVICE_PCI_P2PDMA) have
PageReserved set, so they will not trigger a false positive.

The check no longer blocks the mapping and uses err_printk() to
integrate with dma-debug filtering.

Fixes: f7326196a781 ("dma-mapping: export new dma_*map_phys() interface")
Reviewed-by: Robin Murphy <robin.murphy@arm.com>
Signed-off-by: Jianpeng Chang <jianpeng.chang.cn@windriver.com>
Reviewed-by: Leon Romanovsky <leonro@nvidia.com>
Signed-off-by: Marek Szyprowski <m.szyprowski@samsung.com>
Link: https://lore.kernel.org/r/20260513072209.1486986-1-jianpeng.chang.cn@windriver.com

diff --git a/kernel/dma/debug.c b/kernel/dma/debug.c
index 1a725edbbbf6abec668ec2e115a3ce1504ce9b5c..3248f8b4d096ded67cf76a25811129adb363b79f 100644 (file)
--- a/kernel/dma/debug.c
+++ b/kernel/dma/debug.c
@@ -1251,7 +1251,14 @@ void debug_dma_map_phys(struct device *dev, phys_addr_t phys, size_t size,
        entry->direction = direction;
        entry->map_err_type = MAP_ERR_NOT_CHECKED;
 
-       if (!(attrs & DMA_ATTR_MMIO)) {
+       if (attrs & DMA_ATTR_MMIO) {
+               unsigned long pfn = PHYS_PFN(phys);
+
+               if (pfn_valid(pfn) && !PageReserved(pfn_to_page(pfn)))
+                       err_printk(dev, entry,
+                                  "dma_map_resource called for RAM address %pa\n",
+                                  &phys);
+       } else {
                check_for_stack(dev, phys);
 
                if (!PhysHighMem(phys))

diff --git a/kernel/dma/mapping.c b/kernel/dma/mapping.c
index 23ed8eb9233e552fe520cec14caba4508babc072..e6b07f160d20b3f4bd5e2be5431b29701f61e4de 100644 (file)
--- a/kernel/dma/mapping.c
+++ b/kernel/dma/mapping.c
@@ -365,10 +365,6 @@ EXPORT_SYMBOL(dma_unmap_sg_attrs);
 dma_addr_t dma_map_resource(struct device *dev, phys_addr_t phys_addr,
                size_t size, enum dma_data_direction dir, unsigned long attrs)
 {
-       if (IS_ENABLED(CONFIG_DMA_API_DEBUG) &&
-           WARN_ON_ONCE(pfn_valid(PHYS_PFN(phys_addr))))
-               return DMA_MAPPING_ERROR;
-
        return dma_map_phys(dev, phys_addr, size, dir, attrs | DMA_ATTR_MMIO);
 }
 EXPORT_SYMBOL(dma_map_resource);