Now that we poison/unpoison DMA buffers as part of ownership transfer,
it's possible for us to detect repeated sync's that are unnecessary at a
granularity of cache lines, which was not possible with the initial
approach in commit 1ad4b32702dd ("dma: debug: detect repeated DMA
sync").
Such repeated sync's are usually a result of mapping a buffer and then
calling dma_sync_single_for_device on it. This is unnecessary and warrants
a renewed look at the DMA management scheme, which this warning hopefully
accomplishes.
Signed-off-by: Ahmad Fatoum <a.fatoum@xxxxxxxxxxxxxx>
---
drivers/dma/debug.c | 20 ++++++++++++++++++--
1 file changed, 18 insertions(+), 2 deletions(-)
diff --git a/drivers/dma/debug.c b/drivers/dma/debug.c
index fd279be5be02..01a3832ea30a 100644
--- a/drivers/dma/debug.c
+++ b/drivers/dma/debug.c
@@ -213,7 +213,14 @@ void debug_dma_sync_single_for_cpu(struct device *dev,
cpu_addr = dma_debug_entry_cpu_addr(entry, dma_handle);
if (cpu_addr) {
- kasan_unpoison_shadow(cpu_addr, DMA_KASAN_ALIGN(size));
+ size_t kasan_size = DMA_KASAN_ALIGN(size);
+
+ if (kasan_is_poisoned_shadow(cpu_addr, kasan_size) == 0) {
+ dma_dev_warn(dev, "unexpected sync for CPU of already CPU-mapped %s buffer 0x%llx+0x%zx!\n",
+ dir2name[direction], (u64)dma_handle, size);
+ } else {
+ kasan_unpoison_shadow(cpu_addr, kasan_size);
+ }
}
}
@@ -239,6 +246,15 @@ void debug_dma_sync_single_for_device(struct device *dev,
cpu_addr = dma_debug_entry_cpu_addr(entry, dma_handle);
if (cpu_addr) {
- kasan_poison_shadow(cpu_addr, DMA_KASAN_ALIGN(size), KASAN_DMA_DEV_MAPPED);
+ size_t kasan_size = DMA_KASAN_ALIGN(size);
+
+ /* explicit == 1 check as function may return negative value on error */
+ if (kasan_is_poisoned_shadow(cpu_addr, kasan_size) == 1) {
+ dma_dev_warn(dev, "unexpected sync for device of already device-mapped %s buffer 0x%llx+0x%zx!\n",
+ dir2name[direction], (u64)dma_handle, size);
+ } else {
+ kasan_poison_shadow(cpu_addr, kasan_size, KASAN_DMA_DEV_MAPPED);
+ }
+
}
}
--
2.39.2
