From: Christoph Hellwig <hch@lst.de>
Date: Thu, 12 Apr 2018 10:38:08 +0200
Subject: swiotlb: do not panic on mapping failures
Git-commit: 8088546832aa2c0d8f99dd56edf6384f8a9b63b3
Patch-mainline: v4.20-rc1
References: bsc#1162171

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>
Acked-by: Petr Tesarik <ptesarik@suse.com>
Acked-by: Joerg Roedel <jroedel@suse.de>
---
 kernel/dma/swiotlb.c | 33 +--------------------------------
 1 file changed, 1 insertion(+), 32 deletions(-)

--- a/lib/swiotlb.c
+++ b/lib/swiotlb.c
@@ -799,34 +799,6 @@ swiotlb_free_coherent(struct device *hwd
 }
 EXPORT_SYMBOL(swiotlb_free_coherent);
 
-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.
@@ -855,10 +827,8 @@ dma_addr_t swiotlb_map_page(struct devic
 
 	/* 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 swiotlb_phys_to_dma(dev, io_tlb_overflow_buffer);
-	}
 
 	dev_addr = swiotlb_phys_to_dma(dev, map);
 
@@ -996,7 +966,6 @@ swiotlb_map_sg_attrs(struct device *hwde
 			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);