dma-direct: Make DIRECT_MAPPING_ERROR viable for SWIOTLB
authorRobin Murphy <>
Wed, 21 Nov 2018 16:00:50 +0000 (16:00 +0000)
committerChristoph Hellwig <>
Wed, 21 Nov 2018 17:47:52 +0000 (18:47 +0100)
With the overflow buffer removed, we no longer have a unique address
which is guaranteed not to be a valid DMA target to use as an error
token. The DIRECT_MAPPING_ERROR value of 0 tries to at least represent
an unlikely DMA target, but unfortunately there are already SWIOTLB
users with DMA-able memory at physical address 0 which now gets falsely
treated as a mapping failure and leads to all manner of misbehaviour.

The best we can do to mitigate that is flip DIRECT_MAPPING_ERROR to the
other commonly-used error value of all-bits-set, since the last single
byte of memory is by far the least-likely-valid DMA target.

Fixes: dff8d6c1ed58 ("swiotlb: remove the overflow buffer")
Reported-by: John Stultz <>
Tested-by: John Stultz <>
Acked-by: Konrad Rzeszutek Wilk <>
Signed-off-by: Robin Murphy <>
Signed-off-by: Christoph Hellwig <>

index bd73e7a9141076389ad638cc8fe4f48515331711..9e66bfe369aa057ac9d285d1f3cede42e54387cf 100644 (file)
@@ -5,7 +5,7 @@
 #include <linux/dma-mapping.h>
 #include <linux/mem_encrypt.h>
-#define DIRECT_MAPPING_ERROR           0
+#define DIRECT_MAPPING_ERROR           (~(dma_addr_t)0)
 #include <asm/dma-direct.h>