From d287e4d41be0647aad5f341179f844cf304e0ea5 Mon Sep 17 00:00:00 2001 From: Alejandro Lucero Date: Wed, 18 Jan 2017 12:27:55 +0000 Subject: [PATCH] igb_uio: map dummy DMA forcing IOMMU domain attachment For using a DPDK app when iommu is enabled, it requires to add iommu=pt to the kernel command line. But using igb_uio driver makes DMAR errors because the device has not an IOMMU domain. Since kernel 3.15, iommu=pt requires to use the internal kernel DMA API for attaching the device to the IOMMU 1:1 mapping, aka si_domain. Previous versions did attach the device to that domain when intel iommu notifier was called. This is not a problem if the driver does later some call to the DMA API because the mapping can be done then. But DPDK apps do not use that DMA API at all. Doing this dma map and unmap is harmless even when iommu is not enabled at all. Signed-off-by: Alejandro Lucero Acked-by: Ferruh Yigit --- lib/librte_eal/linuxapp/igb_uio/igb_uio.c | 21 +++++++++++++++++++++ 1 file changed, 21 insertions(+) diff --git a/lib/librte_eal/linuxapp/igb_uio/igb_uio.c b/lib/librte_eal/linuxapp/igb_uio/igb_uio.c index a910eb899a..56d19ab871 100644 --- a/lib/librte_eal/linuxapp/igb_uio/igb_uio.c +++ b/lib/librte_eal/linuxapp/igb_uio/igb_uio.c @@ -326,6 +326,8 @@ igbuio_pci_probe(struct pci_dev *dev, const struct pci_device_id *id) { struct rte_uio_pci_dev *udev; struct msix_entry msix_entry; + dma_addr_t map_dma_addr; + void *map_addr; int err; udev = kzalloc(sizeof(struct rte_uio_pci_dev), GFP_KERNEL); @@ -423,6 +425,25 @@ igbuio_pci_probe(struct pci_dev *dev, const struct pci_device_id *id) dev_info(&dev->dev, "uio device registered with irq %lx\n", udev->info.irq); + /* + * Doing a harmless dma mapping for attaching the device to + * the iommu identity mapping if kernel boots with iommu=pt. + * Note this is not a problem if no IOMMU at all. + */ + map_addr = dma_zalloc_coherent(&dev->dev, 1024, + &map_dma_addr, GFP_KERNEL); + + if (!map_addr) + dev_info(&dev->dev, "dma mapping failed\n"); + else { + dev_info(&dev->dev, "mapping 1K dma=%#llx host=%p\n", + (unsigned long long)map_dma_addr, map_addr); + + dma_free_coherent(&dev->dev, 1024, map_addr, map_dma_addr); + dev_info(&dev->dev, "unmapping 1K dma=%#llx host=%p\n", + (unsigned long long)map_dma_addr, map_addr); + } + return 0; fail_remove_group: -- 2.20.1