Re: [PATCH v2 2/2] swiotlb: Skip cache maintenance on map error

[Stefano Stabellini]

On Wed, 21 Nov 2018, Robin Murphy wrote:
> If swiotlb_bounce_page() failed, calling arch_sync_dma_for_device() may
> lead to such delights as performing cache maintenance on whatever
> address phys_to_virt(SWIOTLB_MAP_ERROR) looks like, which is typically
> outside the kernel memory map and goes about as well as expected.
> 
> Don't do that.
> 
> Fixes: a4a4330db46a ("swiotlb: add support for non-coherent DMA")
> Tested-by: John Stultz 
> Reviewed-by: Christoph Hellwig 
> Signed-off-by: Robin Murphy 

Acked-by: Stefano Stabellini 

> ---
> 
> v2: Collect tags
> 
>  kernel/dma/swiotlb.c | 3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)
> 
> diff --git a/kernel/dma/swiotlb.c b/kernel/dma/swiotlb.c
> index 5731daa09a32..045930e32c0e 100644
> --- a/kernel/dma/swiotlb.c
> +++ b/kernel/dma/swiotlb.c
> @@ -679,7 +679,8 @@ dma_addr_t swiotlb_map_page(struct device *dev, struct 
> page *page,
>   }
>  
>   if (!dev_is_dma_coherent(dev) &&
> - (attrs & DMA_ATTR_SKIP_CPU_SYNC) == 0)
> + (attrs & DMA_ATTR_SKIP_CPU_SYNC) == 0 &&
> + dev_addr != DIRECT_MAPPING_ERROR)
>   arch_sync_dma_for_device(dev, phys, size, dir);
>  
>   return dev_addr;
> -- 
> 2.19.1.dirty
> 
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[PATCH v2 2/2] swiotlb: Skip cache maintenance on map error

[Robin Murphy]

If swiotlb_bounce_page() failed, calling arch_sync_dma_for_device() may
lead to such delights as performing cache maintenance on whatever
address phys_to_virt(SWIOTLB_MAP_ERROR) looks like, which is typically
outside the kernel memory map and goes about as well as expected.

Don't do that.

Fixes: a4a4330db46a ("swiotlb: add support for non-coherent DMA")
Tested-by: John Stultz 
Reviewed-by: Christoph Hellwig 
Signed-off-by: Robin Murphy 
---

v2: Collect tags

 kernel/dma/swiotlb.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/kernel/dma/swiotlb.c b/kernel/dma/swiotlb.c
index 5731daa09a32..045930e32c0e 100644
--- a/kernel/dma/swiotlb.c
+++ b/kernel/dma/swiotlb.c
@@ -679,7 +679,8 @@ dma_addr_t swiotlb_map_page(struct device *dev, struct page 
*page,
}
 
if (!dev_is_dma_coherent(dev) &&
-   (attrs & DMA_ATTR_SKIP_CPU_SYNC) == 0)
+   (attrs & DMA_ATTR_SKIP_CPU_SYNC) == 0 &&
+   dev_addr != DIRECT_MAPPING_ERROR)
arch_sync_dma_for_device(dev, phys, size, dir);
 
return dev_addr;
-- 
2.19.1.dirty

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