Commit 370645f41e6e ("dma-mapping: force bouncing if the kmalloc() size
is not cache-line-aligned") introduced DMA_BOUNCE_UNALIGNED_KMALLOC
feature and lets architecture specific code to configure kmalloc slabs
with sizes smaller than the value of dma_get_cache_alignment().
When that feature is enabled, the physical address of some small
kmalloc()-ed buffers might be not aligned to the CPU cachelines, thus not
really suitable for typical DMA. To properly handle that case a SWIOTLB
buffer bouncing is used, so no CPU cache corruption occurs. When that
happens, there is no point reporting a false-positive DMA-API warning
that the buffer is not properly aligned, as this is not a client driver
fault.
Fixes: 370645f41e6e ("dma-mapping: force bouncing if the kmalloc() size is not cache-line-aligned")
Signed-off-by: Marek Szyprowski <m.szyprowski@samsung.com>
Reviewed-by: Catalin Marinas <catalin.marinas@arm.com>
---
v2:
- replaced is_swiotlb_allocated() with is_swiotlb_active(entry->dev) as
suggested by Catalin
v1: https://lore.kernel.org/all/20251009141508.2342138-1-m.szyprowski@samsung.com/
---
kernel/dma/debug.c | 5 ++++-
1 file changed, 4 insertions(+), 1 deletion(-)
diff --git a/kernel/dma/debug.c b/kernel/dma/debug.c
index b82399437db0..7458382be840 100644
--- a/kernel/dma/debug.c
+++ b/kernel/dma/debug.c
@@ -23,6 +23,7 @@
#include <linux/ctype.h>
#include <linux/list.h>
#include <linux/slab.h>
+#include <linux/swiotlb.h>
#include <asm/sections.h>
#include "debug.h"
@@ -594,7 +595,9 @@ static void add_dma_entry(struct dma_debug_entry *entry, unsigned long attrs)
if (rc == -ENOMEM) {
pr_err_once("cacheline tracking ENOMEM, dma-debug disabled\n");
global_disable = true;
- } else if (rc == -EEXIST && !(attrs & DMA_ATTR_SKIP_CPU_SYNC)) {
+ } else if (rc == -EEXIST && !(attrs & DMA_ATTR_SKIP_CPU_SYNC) &&
+ !(IS_ENABLED(CONFIG_DMA_BOUNCE_UNALIGNED_KMALLOC) &&
+ is_swiotlb_active(entry->dev))) {
err_printk(entry->dev, entry,
"cacheline tracking EEXIST, overlapping mappings aren't supported\n");
}
--
2.34.1