[Xen-devel] [PATCH 02/24] swiotlb: Skip cache maintenance on map error

[Christoph Hellwig <hch@xxxxxx>]

From: Robin Murphy <robin.murphy@xxxxxxx>

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 <john.stultz@xxxxxxxxxx>
Signed-off-by: Robin Murphy <robin.murphy@xxxxxxx>
Signed-off-by: Christoph Hellwig <hch@xxxxxx>
---
 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


_______________________________________________
Xen-devel mailing list
Xen-devel@xxxxxxxxxxxxxxxxxxxx
https://lists.xenproject.org/mailman/listinfo/xen-devel