The patch titled
Subject: dma-debug: update DMA debug API to better handle multiple mappings of a buffer
has been removed from the -mm tree. Its filename was
dma-debug-update-dma-debug-api-to-better-handle-multiple-mappings-of-a-buffer.patch
This patch was dropped because it was merged into mainline or a subsystem tree
------------------------------------------------------
From: Alexander Duyck <alexander.h.duyck@xxxxxxxxx>
Subject: dma-debug: update DMA debug API to better handle multiple mappings of a buffer
There were reports of the igb driver unmapping buffers without calling
dma_mapping_error. On closer inspection issues were found in the DMA
debug API and how it handled multiple mappings of the same buffer.
The issue I found is the fact that the debug_dma_mapping_error would only
set the map_err_type to MAP_ERR_CHECKED in the case that the was only one
match for device and device address. However in the case of non-IOMMU,
multiple addresses existed and as a result it was not setting this field
once a second mapping was instantiated. I have resolved this by changing
the search so that it instead will now set MAP_ERR_CHECKED on the first
buffer that matches the device and DMA address that is currently in the
state MAP_ERR_NOT_CHECKED.
A secondary side effect of this patch is that in the case of multiple
buffers using the same address only the last mapping will have a valid
map_err_type. The previous mappings will all end up with map_err_type set
to MAP_ERR_CHECKED because of the dma_mapping_error call in
debug_dma_map_page. However this behavior may be preferable as it means
you will likely only see one real error per multi-mapped buffer, versus
the current behavior of multiple false errors mer multi-mapped buffer.
Signed-off-by: Alexander Duyck <alexander.h.duyck@xxxxxxxxx>
Cc: Joerg Roedel <joro@xxxxxxxxxx>
Reviewed-by: Shuah Khan <shuah.khan@xxxxxx>
Tested-by: Shuah Khan <shuah.khan@xxxxxx>
Cc: Jakub Kicinski <kubakici@xxxxx>
Cc: Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
lib/dma-debug.c | 24 +++++++++++++++++++-----
1 file changed, 19 insertions(+), 5 deletions(-)
diff -puN lib/dma-debug.c~dma-debug-update-dma-debug-api-to-better-handle-multiple-mappings-of-a-buffer lib/dma-debug.c
--- a/lib/dma-debug.c~dma-debug-update-dma-debug-api-to-better-handle-multiple-mappings-of-a-buffer
+++ a/lib/dma-debug.c
@@ -1085,13 +1085,27 @@ void debug_dma_mapping_error(struct devi
ref.dev = dev;
ref.dev_addr = dma_addr;
bucket = get_hash_bucket(&ref, &flags);
- entry = bucket_find_exact(bucket, &ref);
- if (!entry)
- goto out;
+ list_for_each_entry(entry, &bucket->list, list) {
+ if (!exact_match(&ref, entry))
+ continue;
+
+ /*
+ * The same physical address can be mapped multiple
+ * times. Without a hardware IOMMU this results in the
+ * same device addresses being put into the dma-debug
+ * hash multiple times too. This can result in false
+ * positives being reported. Therefore we implement a
+ * best-fit algorithm here which updates the first entry
+ * from the hash which fits the reference value and is
+ * not currently listed as being checked.
+ */
+ if (entry->map_err_type == MAP_ERR_NOT_CHECKED) {
+ entry->map_err_type = MAP_ERR_CHECKED;
+ break;
+ }
+ }
- entry->map_err_type = MAP_ERR_CHECKED;
-out:
put_hash_bucket(bucket, &flags);
}
EXPORT_SYMBOL(debug_dma_mapping_error);
_
Patches currently in -mm which might be from alexander.h.duyck@xxxxxxxxx are
linux-next.patch
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