[vfio-users] [External Email] Re: Direct Assignment of Non-PCI devices to VM

[Micah Morton]

On Wed, Nov 4, 2020 at 1:32 PM Roja Eswaran <reswara1 at binghamton.edu> wrote:
>
> Sorry for the previous email. Here is the email with Plaintext.
>
>
> --
> Thanks,
> Roja Eswaran
> PhD Student, Operating Systems and Networks Laboratory
> State University of New York, Binghamton
>
>
> ---------- Forwarded message ---------
> From: Roja Eswaran <reswara1 at binghamton.edu>
> Date: Wed, Nov 4, 2020 at 6:31 PM
> Subject: Re: [External Email] Re: [vfio-users] Direct Assignment of
> Non-PCI devices to VM
> To: Micah Morton <mortonm at chromium.org>
> Cc: Auger Eric <eric.auger at redhat.com>, <vfio-users at redhat.com>
>
>
> Mr. Morton,
> Thank you so much for your insights. I have one quick question. Are
> there any drivers other than VFIO that could be used with QEMU for the
> direct assignment? Please let me know if you're aware of any such
> drivers. Thanks again!

AFAIK no -- the UIO driver is the next closest thing but QEMU doesn't
have any support for using it to assign HW devices to guest VMs.

> --
> Thanks,
> Roja Eswaran
> PhD Student, Operating Systems and Networks Laboratory
> State University of New York, Binghamton
>
>
> On Wed, Nov 4, 2020 at 3:25 PM Micah Morton <mortonm at chromium.org> wrote:
> >
> > On Wed, Nov 4, 2020 at 5:30 AM Roja Eswaran <reswara1 at binghamton.edu> wrote:
> > >
> > > I am using Jetson Xavier NX which integrates a Realtek RTL8211FDI Gigabit Ethernet controller.  The on-module Ethernet controller supports 10/100/1000 Gigabit Ethernet IEEE 802.3u Media Access Controller (MAC).
> > >  I am trying to assign Non-PCI NIC mentioned above directly to the Vanilla VM. As it's not a PCI device, I have no idea how I can achieve this.
> > >
> > > 1) Is it possible to do a direct assignment on Non-PCI devise to VM using VFIO drivers?
> >
> > I don't see any mention of an IOMMU in any of these 3 DT files:
> >
> > https://elixir.bootlin.com/linux/latest/source/arch/arm64/boot/dts/nvidia/tegra194-p2972-0000.dts
> > https://elixir.bootlin.com/linux/latest/source/arch/arm64/boot/dts/nvidia/tegra194-p2888.dtsi
> > https://elixir.bootlin.com/linux/latest/source/arch/arm64/boot/dts/nvidia/tegra194.dtsi
> >
> > Does the Jetson Xavier NX board have an iommu? If not, this is the
> > most fundamental reason you wouldn't be able to use VFIO for
> > assignment on that board -- especially if the ethernet controller is
> > DMA-capable, since you won't be able to ensure the ethernet device's
> > DMAs operate on the memory assigned to the guest.
> >
> > You could check for this by doing "dmesg | grep -i -e iommu -e smmu"
> > on the device and seeing if it prints anything, or looking at
> > /sys/kernel/iommu_groups to see if that dir exists.
> >
> > Beyond the IOMMU, vfio-platform/QEMU in their current state wouldn't
> > be able to handle the embedded PHY device here:
> > https://elixir.bootlin.com/linux/latest/source/arch/arm64/boot/dts/nvidia/tegra194-p2888.dtsi#L43
> > , which would be another hurdle.
> >
> > > 2) If not, are there any other drivers that would help me achieve the direct assignment?
> > > The direct assignment is important because we are trying to reduce the CPU utilization even though virtio drivers give us a very small network latency overhead. Any comments or insights are really appreciated. Thank you so much for your time!
> > >
> > >
> > > --
> > > Thanks,
> > > Roja Eswaran
> > > Ph.D. Student, Operating Systems and Networks Laboratory
> > > State University of New York, Binghamton
> > > _______________________________________________
> > > vfio-users mailing list
> > > vfio-users at redhat.com
> > > https://www.redhat.com/mailman/listinfo/vfio-users