Thanks Alex. >> Without an iommu in the VM, you'd be limited to no-iommu support for VM >> userspace, So are you trying to say VFIO NO-IOMMU should work inside VM. Does that mean VFIO NO-IOMMU in VM and VFIO IOMMU in host for same device is a legitimate configuration? I did tried this configuration and the application (in VM) seems to get container_fd, group_fd, device_fd successfully but after VFIO_DEVICE_RESET ioctl the PCI link breaks from VM as well as from host. This could be specific to PCI endpoint device which I can dig.
I will be happy if VFIO NO-IOMMU in VM and IOMMU in host for same device is legitimate configuration. Thanks Nitin On Thu, Jun 22, 2017 at 10:29 PM, Alex Williamson <alex.william...@redhat.com> wrote: > [cc +qemu-devel, +peterx] > > On Thu, 22 Jun 2017 22:18:06 +0530 > Nitin Saxena <nitin....@gmail.com> wrote: > >> Hi, >> >> I have a PCI device connected as an endpoint to Intel host machine. >> The requirement is to run dpdk like user space data path application >> in VM using PCI PF passthrough (SRIOV disabled). This application >> works fine on host kernel and uses VFIO to get MSIX interrupts from >> PCI device. We are trying to run this existing application in VM using >> PCI passthrough. This application has capability to use >> VFIO_IOMMU_TYPE1 as wells as VFIO_NOIOMMU. >> >> On Intel host machine VT-d has been enabled and using virt-manager PCI >> device PF is assigned to the VM. This makes virt-manager to implicitly >> binds PCI device PF to vfio with vfio_iommu_type1. The VM LINUX kernel >> was booted with intel_iommu=on as boot parameter. >> >> My question: Is it possible that vfio can coexist in host (by >> virt-manager) as well as VM (by application)? If yes, does application >> running inside VM needs to configure VFIO with iommu_type=IOMMU or >> iommu_type=no-iommu. >> >> In VM I tried inserting vfio_iommu_type1.ko kernel module which failed >> with "No such device error". Thats why I am confused whether my >> requirement is legitimate or not. What could be the best solution? > > This is really more of a QEMU question. In order to use > vfio_iommu_type1 in the guest, you need an iommu in the guest. The > most recent release of QEMU supports this with an emulated VT-d > device. Therefore if you create a VM with emulated VT-d and a device > assigned through vfio-pci, you can expose it to userspace in the VM with > physical iommu protection. Without an iommu in the VM, you'd be > limited to no-iommu support for VM userspace, the physical iommu would > only protect the device to the extent of VM memory, no to specific > userspace mappings within the VM. Thanks, > > Alex
