On Fri, Feb 10, 2017 at 7:06 PM, Ferruh Yigit <ferruh.yi...@intel.com> wrote:
> On 2/10/2017 7:03 PM, Ferruh Yigit wrote: > > On 2/8/2017 11:54 AM, Alejandro Lucero wrote: > >> Hi Ferruh, > >> > >> On Tue, Feb 7, 2017 at 3:59 PM, Ferruh Yigit <ferruh.yi...@intel.com > >> <mailto:ferruh.yi...@intel.com>> wrote: > >> > >> Hi Alejandro, > >> > >> On 1/18/2017 12:27 PM, Alejandro Lucero wrote: > >> > 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. > >> > >> Please help to understand the scope of the problem, > >> > >> > >> After reading your reply, I realize I could have explained it better. > >> First of all, this is related to SRIOV, exactly when the VFs are > created. > >> > >> > >> 1- How can you re-produce the problem? > >> > >> > >> Using a VF from a Intel card by a DPDK app in the host and a kernel >= > >> 3.15. Although usually VFs are assigned to VMs, it could also be an > >> option to use VFs by the host. > >> > >> BTW, I did not try to reproduce the problem with an Intel card. I > >> triggered this problem with an NFP, but because the problem behind, I > >> bet that is going to happen for an Intel one as well. > > > > I can able to reproduce the problem with ixgbe, by using VF on the host. > > > > And I verified your patch fixes it, it cause device attached to a vfio > > group. > > I want to send this in a separate mail, since not directly related to > your patch, but while I was testing with vfio-pci I get lower numbers > comparing to the igb_uio, which is unexpected AFAIK. > > Most probably I am doing something wrong, but I would like to ask if are > you observing same behavior? > Can you tell me which test are you running? Although both, igb_uio and vfio, allow to work with IOMMU, the first one requires iommu=pt. It implies a single IOMMU domain already created by the system with the 1:1 mapping being used. With VFIO, a specific per device IOMMU domain is created. Depending on how are you measuring performance, that specific IOMMU domain creation by the DPDK app could have an impact, but I do not think that should be really significant. But with IOMMU you have the same problem than with MMU, there is a IOTLB for IOMMU as there is a TLB for MMU. Depending on the app, some IOMMU/IOTLB contention is likely. I have done some experiments and still investigating this during my spare time. It would be worth a talk about this in the next DPDK meeting. > > Thanks, > ferruh > >
