6.6-stable review patch. If anyone has any objections, please let me know.
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From: Marek Szyprowski m.szyprowski@samsung.com
commit 03521c892bb8d0712c23e158ae9bdf8705897df8 upstream.
Commit 370645f41e6e ("dma-mapping: force bouncing if the kmalloc() size is not cache-line-aligned") introduced DMA_BOUNCE_UNALIGNED_KMALLOC feature and permitted architecture specific code 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.
[m.szyprowski@samsung.com: replace is_swiotlb_allocated() with is_swiotlb_active(), per Catalin] Link: https://lkml.kernel.org/r/20251010173009.3916215-1-m.szyprowski@samsung.com Link: https://lkml.kernel.org/r/20251009141508.2342138-1-m.szyprowski@samsung.com 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 Cc: Christoph Hellwig hch@lst.de Cc: Inki Dae m.szyprowski@samsung.com Cc: Robin Murohy robin.murphy@arm.com Cc: "Isaac J. Manjarres" isaacmanjarres@google.com Cc: stable@vger.kernel.org Signed-off-by: Andrew Morton akpm@linux-foundation.org Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- kernel/dma/debug.c | 5 ++++- 1 file changed, 4 insertions(+), 1 deletion(-)
--- 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"
@@ -601,7 +602,9 @@ static void add_dma_entry(struct dma_deb 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"); }