Messages in this thread | | | Date | Thu, 18 Oct 2018 20:18:03 -0400 | From | Konrad Rzeszutek Wilk <> | Subject | Re: [PATCH 03/10] swiotlb: do not panic on mapping failures |
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On Thu, Oct 11, 2018 at 07:06:31PM +0100, Robin Murphy wrote: > On 08/10/18 09:02, Christoph Hellwig wrote: > > 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. > > $ git grep -l 'dma_map_\(page\|single\)' drivers/ | wc -l > 385 > $ git grep -l dma_mapping_error drivers/ | wc -l > 396 > > Close enough, to first approximation :D > > I agree the other (non-fatal) warning seems sufficient, and frankly the > panic can be a bit of a pain for development sometimes.
What would you recommend instead? > > Reviewed-by: Robin Murphy <robin.murphy@arm.com> > > > 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); > >
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