Re: [dpdk-dev] Accessing a Virtual Function Driver in Guest Machine via VFIO

[Aashima Arora <arora.aa91@gmail.com>]

Thanks for your reply.

What do you mean "device assignment" ? You mean pass-through?
> Yes, the same thing. Pass through of PCI device to VM via qemu
(pci-assign, vfio-pci, ivshmem etc)

As I knows, the answer is *NO*,  because the iommu is not support in guest.
> NO was essentially what I was looking for, aware of it now :)



On Wed, Dec 10, 2014 at 12:42 PM, Qiu, Michael <michael.qiu@intel.com>
wrote:

> On 12/6/2014 3:01 AM, Aashima Arora wrote:
> > Hi,
> > I was trying to access the pci config space(BAR) of the virtual function
> > device visible in the virtual machine, similar to what DPDK does on host
> > via both UIO and VFIO. Did the following steps.
> >
> > 1. Bound PF Drivers to ixgbe and spawned virtual function drivers , bound
> > them to vfio-pci and set their mac addresses via ip link.  Ran Qemu and
> > assigned the VF Device using vfio-pci device assignment and initialized
> the
> > virtual machine.
> > insmod igb max_vfs=2
> >
> > ./x86_64-softmmu/qemu-system-x86_64 -cpu host -boot c -hda
> > /home/vm-images/vm2.imgsnapshot -m 2048M -smp 2 --enable-kvm -name 'vm2'
> > -vnc :2 -pidfile /tmp/vm2.pid -driile=fat:rw:/tmp/share,snapshot=off
> > -device vfio-pci,host=01:10.1,id=net1
> >
> >
> > 2.  The VF Device was visible with another pci address.
> >
> > 00:04.0 Ethernet controller: Intel Corporation 82599ES 10-Gigabit
> SFI/SFP+
> > Network
> > Connection (rev 01)
> >
> > Further ran DPDK testpmd on top of VM but bound the virtual function
> driver
> > to igb_uio instead of vfio-pci. It ran successfully.  The ixgbevf pmd
> > driver is able to access the BAR registers in pci_uio_map_resource via
> > mmaping somewhere close to hugepages. I was not able to bind the virtual
> > function driver in VM to vfio-pci and hence DPDK would not be able to run
> > with VFIO enabled as it complains of no IOMMU support. I also believe
> that
> > there is little logic in binding the vf device to vfio-pci again since
> qemu
> > has already taken care of it and hardware support is involved.
> >
> > So my questions are
> > a. vfio is meant to be  a replacement for both uio and device assignment
> > for qemu. This doesnt seem simultaneous. Comment?
>
> What do you mean "device assignment" ? You mean pass-through?
> > b. Is there any way to access VF device  using VFIO in guest userspace?
> > Have you run DPDK in guest machine with VFIO support enabled and all
> > dependent modules inserted and did it work?
>
> As I knows, the answer is *NO*,  because the iommu is not support in guest.
> > c. Is igb_uio or uio_pci_generic in future the only way  to access the
> > device in guest userspace?
>
> It depends, who knows what will happen in future :)
>
> Thanks,
> Michael
> > *Regards*
> >
>
>


-- 
*Regards,*

*Aashima Arora*

*arora.aa91@gmail.com <arora.aa91@gmail.com>*