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27 March 2024, 02:37:15 UTC
Revision b34087157dd76e8d96e5e52808134a791ac61e57 authored by Robin Murphy on 21 November 2018, 16:00:50 UTC, committed by Christoph Hellwig on 21 November 2018, 17:47:52 UTC 
dma-direct: Make DIRECT_MAPPING_ERROR viable for SWIOTLB
 
With the overflow buffer removed, we no longer have a unique address
which is guaranteed not to be a valid DMA target to use as an error
token. The DIRECT_MAPPING_ERROR value of 0 tries to at least represent
an unlikely DMA target, but unfortunately there are already SWIOTLB
users with DMA-able memory at physical address 0 which now gets falsely
treated as a mapping failure and leads to all manner of misbehaviour.

The best we can do to mitigate that is flip DIRECT_MAPPING_ERROR to the
other commonly-used error value of all-bits-set, since the last single
byte of memory is by far the least-likely-valid DMA target.

Fixes: dff8d6c1ed58 ("swiotlb: remove the overflow buffer")
Reported-by: John Stultz <john.stultz@linaro.org>
Tested-by: John Stultz <john.stultz@linaro.org>
Acked-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Signed-off-by: Robin Murphy <robin.murphy@arm.com>
Signed-off-by: Christoph Hellwig <hch@lst.de>
1 parent c8ce94b
History
Tip revision: b34087157dd76e8d96e5e52808134a791ac61e57 authored by Robin Murphy on 21 November 2018, 16:00:50 UTC
dma-direct: Make DIRECT_MAPPING_ERROR viable for SWIOTLB
Tip revision: b340871
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