2015-12-16 01:39:05

by Daniel Mentz

Subject: [PATCH] dma-debug: Fix dma_debug_entry offset calculation

dma-debug uses struct dma_debug_entry to keep track of dma coherent
memory allocation requests. The virtual address is converted into a pfn
and an offset. Previously, the offset was calculated using an incorrect
bit mask. As a result, we saw incorrect error messages from dma-debug
like the following:

"DMA-API: exceeded 7 overlapping mappings of cacheline 0x03e00000"

Cacheline 0x03e00000 does not exist on our platform.

Fixes: 0abdd7a81b7e ("dma-debug: introduce debug_dma_assert_idle()")
Signed-off-by: Daniel Mentz <[email protected]>
---
lib/dma-debug.c | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/lib/dma-debug.c b/lib/dma-debug.c
index 8855f01..d34bd24 100644
--- a/lib/dma-debug.c
+++ b/lib/dma-debug.c
@@ -1464,7 +1464,7 @@ void debug_dma_alloc_coherent(struct device *dev, size_t size,
entry->type = dma_debug_coherent;
entry->dev = dev;
entry->pfn = page_to_pfn(virt_to_page(virt));
- entry->offset = (size_t) virt & PAGE_MASK;
+ entry->offset = (size_t) virt & ~PAGE_MASK;
entry->size = size;
entry->dev_addr = dma_addr;
entry->direction = DMA_BIDIRECTIONAL;
@@ -1480,7 +1480,7 @@ void debug_dma_free_coherent(struct device *dev, size_t size,
.type = dma_debug_coherent,
.dev = dev,
.pfn = page_to_pfn(virt_to_page(virt)),
- .offset = (size_t) virt & PAGE_MASK,
+ .offset = (size_t) virt & ~PAGE_MASK,
.dev_addr = addr,
.size = size,
.direction = DMA_BIDIRECTIONAL,
--
2.6.0.rc2.230.g3dd15c0

2015-12-16 19:00:48

by Dan Williams

Subject: Re: [PATCH] dma-debug: Fix dma_debug_entry offset calculation

On Tue, Dec 15, 2015 at 5:38 PM, Daniel Mentz <[email protected]> wrote:
> dma-debug uses struct dma_debug_entry to keep track of dma coherent
> memory allocation requests. The virtual address is converted into a pfn
> and an offset. Previously, the offset was calculated using an incorrect
> bit mask. As a result, we saw incorrect error messages from dma-debug
> like the following:
>
> "DMA-API: exceeded 7 overlapping mappings of cacheline 0x03e00000"
>
> Cacheline 0x03e00000 does not exist on our platform.
>
> Fixes: 0abdd7a81b7e ("dma-debug: introduce debug_dma_assert_idle()")
> Signed-off-by: Daniel Mentz <[email protected]>

Looks good, thanks Daniel! I'll include this with some other fixes
I'm pushing up later today.