Re: [dpdk-dev] [PATCH v1] igu_uio: fix IOMMU domain issue

[Thomas Monjalon <thomas.monjalon@6wind.com>]

Ping, this patch is stalled.

2016-05-11 18:24, Ferruh Yigit:
> On 5/11/2016 8:35 AM, Alejandro Lucero wrote:
> > On Tue, May 10, 2016 at 4:59 PM, Stephen Hemminger <
> > stephen@networkplumber.org> wrote:
> > 
> >> On Tue, 10 May 2016 19:21:41 +0800
> >> Zhe Tao <zhe.tao@intel.com> wrote:
> >>
> >>> Problem:
> >>> The following  operations will cause the igb_uio based DPDK
> >>> operation failed.
> >>> --Any device assignment through the kvm_assign_device interface,
> >>> this can be the pci-assign method in QEMU
> >>> --VFIO group attachment operation(attach to the container)
> >>> this can happens in  vfio-pci assignment in QEMU
> >>
> >>
> >> If you have an IOMMU why not use VFIO instead, it is better.
> >>
> > 
> > It is not about VFIO against UIO but about how iommu domains are created
> > and destroyed by the (old) kernel when iommu=pt. So even with VFIO you can
> > have problems.
> 
> Problem is in IOMMU driver but we are adding a workaround to igb_uio, if
> using VFIO solves the issue, I believe that is better workaround.
> 
> 1) Is there any case IOMMU supported but VFIO is not supported? Is there
> anything forces to use igb_uio?
> 
> 2) Does using VFIO solves the issue defined in problem statement?
> 
> > 
> > We have had problems like this and other due to our device (NFP) just
> > mapping up to 40 bits of address space. Old kernels used in LTS
> > distributions like Ubuntu are iommu buggy and you need to do things like
> > this mapping inside the driver for solving problems. By the way, using
> > SRIOV just adds more problems. It is not safe to use iommu=pt with 3.13.x
> > Ubuntu kernels.
> > 
> > It would be a good thing for the original patch to identify those kernels
> > where the problem was detected. Of course, there could be more kernels with
> > the same problem but that is more work to do.
> > 
> 
> Thanks,
> ferruh