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Subject[PATCH 03/10] swiotlb: do not panic on mapping failures
Date
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 swace we can
also remove swiotlb_full entirely as it serves no purpose now.

Signed-off-by: Christoph Hellwig <hch@lst.de>
---
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 26d3af52956f..69bf305ee5f8 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);

@@ -948,7 +918,6 @@ 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);
--
2.19.0
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