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    Subject[PATCH 4.19 105/306] swiotlb: do not panic on mapping failures
    Date
    From: Christoph Hellwig <hch@lst.de>

    [ Upstream commit 8088546832aa2c0d8f99dd56edf6384f8a9b63b3 ]

    All properly written drivers now have error handling in the
    dma_map_single / dma_map_page callers. As swiotlb_tbl_map_single already
    prints a useful warning when running out of swiotlb pool space we can
    also remove swiotlb_full entirely as it serves no purpose now.

    Signed-off-by: Christoph Hellwig <hch@lst.de>
    Reviewed-by: Robin Murphy <robin.murphy@arm.com>
    Signed-off-by: Sasha Levin <sashal@kernel.org>
    ---
    kernel/dma/swiotlb.c | 33 +--------------------------------
    1 file changed, 1 insertion(+), 32 deletions(-)

    diff --git a/kernel/dma/swiotlb.c b/kernel/dma/swiotlb.c
    index 4f8a6dbf0b609..2a8c41f12d450 100644
    --- a/kernel/dma/swiotlb.c
    +++ b/kernel/dma/swiotlb.c
    @@ -761,34 +761,6 @@ static bool swiotlb_free_buffer(struct device *dev, size_t size,
    return true;
    }

    -static void
    -swiotlb_full(struct device *dev, size_t size, enum dma_data_direction dir,
    - int do_panic)
    -{
    - if (swiotlb_force == SWIOTLB_NO_FORCE)
    - return;
    -
    - /*
    - * Ran out of IOMMU space for this operation. This is very bad.
    - * Unfortunately the drivers cannot handle this operation properly.
    - * unless they check for dma_mapping_error (most don't)
    - * When the mapping is small enough return a static buffer to limit
    - * the damage, or panic when the transfer is too big.
    - */
    - dev_err_ratelimited(dev, "DMA: Out of SW-IOMMU space for %zu bytes\n",
    - size);
    -
    - if (size <= io_tlb_overflow || !do_panic)
    - return;
    -
    - if (dir == DMA_BIDIRECTIONAL)
    - panic("DMA: Random memory could be DMA accessed\n");
    - if (dir == DMA_FROM_DEVICE)
    - panic("DMA: Random memory could be DMA written\n");
    - if (dir == DMA_TO_DEVICE)
    - panic("DMA: Random memory could be DMA read\n");
    -}
    -
    /*
    * Map a single buffer of the indicated size for DMA in streaming mode. The
    * physical address to use is returned.
    @@ -817,10 +789,8 @@ dma_addr_t swiotlb_map_page(struct device *dev, struct page *page,

    /* Oh well, have to allocate and map a bounce buffer. */
    map = map_single(dev, phys, size, dir, attrs);
    - if (map == SWIOTLB_MAP_ERROR) {
    - swiotlb_full(dev, size, dir, 1);
    + if (map == SWIOTLB_MAP_ERROR)
    return __phys_to_dma(dev, io_tlb_overflow_buffer);
    - }

    dev_addr = __phys_to_dma(dev, map);

    @@ -954,7 +924,6 @@ swiotlb_map_sg_attrs(struct device *hwdev, struct scatterlist *sgl, int nelems,
    if (map == SWIOTLB_MAP_ERROR) {
    /* Don't panic here, we expect map_sg users
    to do proper error handling. */
    - swiotlb_full(hwdev, sg->length, dir, 0);
    attrs |= DMA_ATTR_SKIP_CPU_SYNC;
    swiotlb_unmap_sg_attrs(hwdev, sgl, i, dir,
    attrs);
    --
    2.20.1


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