On Fri, Oct 01, 2021 at 06:19:59AM +0200, Christoph Hellwig wrote: > On Tue, Sep 14, 2021 at 03:45:06PM +0000, Ioana Ciornei wrote: > > [ 245.927020] fsl_dpaa2_eth dpni.3: scather-gather idx 0 P=20a7320000 > > N=20a7320 D=20a7320000 L=30 DMA_BIDIRECTIONAL dma map error check not > > applicableĀ· > > [ 245.927048] fsl_dpaa2_eth dpni.3: scather-gather idx 1 P=20a7320030 > > N=20a7320 D=20a7320030 L=5a8 DMA_BIDIRECTIONAL dma map error check not > > applicable > > [ 245.927062] DMA-API: cacheline tracking EEXIST, overlapping mappings > > aren't supported > > > > The first line is the dump of the dma_debug_entry which is already present > > in the radix tree and the second one is the entry which just triggered > > the EEXIST. > > > > As we can see, they are not actually overlapping, at least from my > > understanding. The first one starts at 0x20a7320000 with a size 0x30 > > and the second one at 0x20a7320030. > > They overlap the cache lines. Which means if you use this driver > on a system that is not dma coherent you will corrupt data.
This is a driver of an integrated ethernet controller which is DMA coherent. I added a print just to make sure of this: --- a/kernel/dma/debug.c +++ b/kernel/dma/debug.c @@ -567,6 +567,7 @@ static void add_dma_entry(struct dma_debug_entry *entry) pr_err("cacheline tracking ENOMEM, dma-debug disabled\n"); global_disable = true; } else if (rc == -EEXIST) { + pr_err("dev_is_dma_coherent(%s) = %d\n", dev_name(entry->dev), dev_is_dma_coherent(entry->dev)); err_printk(entry->dev, entry, "cacheline tracking EEXIST, overlapping mappings aren't supported\n"); } [ 85.852218] DMA-API: dev_is_dma_coherent(dpni.3) = 1 [ 85.858891] ------------[ cut here ]------------ [ 85.858893] DMA-API: fsl_dpaa2_eth dpni.3: cacheline tracking EEXIST, overlapping mappings aren't supported [ 85.858901] WARNING: CPU: 13 PID: 1046 at kernel/dma/debug.c:571 add_dma_entry+0x330/0x390 [ 85.858911] Modules linked in: [ 85.858915] CPU: 13 PID: 1046 Comm: iperf3 Not tainted 5.15.0-rc2-00478-g34286ba6a164-dirty #1275 [ 85.858919] Hardware name: NXP Layerscape LX2160ARDB (DT) Shouldn't this case not generate this kind of warning? Ioana _______________________________________________ iommu mailing list iommu@lists.linux-foundation.org https://lists.linuxfoundation.org/mailman/listinfo/iommu