Hi, To understand the issue, you may have a look at: http://www.intel.com/content/www/us/en/intelligent-systems/intel-technology/ vt-directed-io-spec.html
When you have no IOMMU, "physical" address space is accessed directly by hardware, so your core works. When VT-d is active, there is DMA/IRQ remapping hardware layer between the device and the memory/cpu. If you look at ?3.4.3 of the spec, you that for each device of each bus there is a context (enumerated at boot time, leveraging BIOS/ACPI). For each device, you may have address translation programmed so that DMA produced by hardware is actually mapped to a physical address. When you use the Linux kernel API for mapping DMA memory, Linux takes care of the "details". For DPDK, documentation ?5.6 Using Linux IOMMU Pass-Through to Run Intel? DPDK with Intel? VT-d says that you should have iommu=pt kernel parameter on. Do you have it ? FF > -----Message d'origine----- > De?: dev [mailto:dev-bounces at dpdk.org] De la part de Sridhar S > Envoy??: dimanche 5 janvier 2014 13:38 > ??: dev at dpdk.org > Objet?: [dpdk-dev] Issue when the kernel parameter intel_iommu=on is being > used > > Hello, > > > > I am using DPDK 1.5 for development of host pmd for device ?Connect X3?. > > > > I am observing issue while the ConnectX3 device DMA to a memory which is > allocated with rte_memzone_reserve_aligned() API . > > The issue(please refer ERROR below) has been observed if the system runs > with the kernel parameter ?intel_iommu=on?. > > > > ERROR : > > dmar: DRHD: handling fault status reg 302 > > dmar: DMAR:[DMA Write] Request device [01:00.0] fault addr 4f883000 > > DMAR:[fault reason 01] Present bit in root entry is clear > > > The reported "fault Addr" is the physical address which was returned by the > Above API. > > > > I don?t see any issue with the same code when the system up with kernel > parameter intel_iommu=off. > > > > > Can you share your comments on this issue? > > > Thanks in advance > > Sri
