[dpdk-dev] VFIO no-iommu

Alejandro Lucero alejandro.lucero at netronome.com
Tue Dec 15 12:20:47 CET 2015


Hi,

I know a bit about VFIO implementation, have been debugging IOMMU (intel)
problems,  know how QEMU/KVM work about using legacy or vfio attached
devices, and I'm the maintainer of a DPDK PMD recently accepted upstream
which requires our particular UIO driver (not maintained upstream). So I
guess I could help with this effort and testing the code with our card. Of
course, I can not be full time on this but I will be happy to contribute.


On Fri, Dec 11, 2015 at 11:20 PM, Jan Viktorin <viktorin at rehivetech.com>
wrote:

> Hello,
>
> I am not involved in the vfio very much, however, I was watching some
> vfio-related code in last few weeks. It looks promising to me and
> IMHO it seems to the best way to bring a support of integrated Ethernet
> MACs into DPDK (related to many SoCs). Unfortunately, the ARMv7 SoCs (I
> know) lacks of an IOMMU... The only protection there is the TrustZone
> technology but I have no idea of its support in the kernel. It's also
> far from being a replacement of an IOMMU. When using FPGAs, it is
> possible to put an IOMMU engine there (I've got such a prototype
> somewhere in my VHDL library) but nobody will probably do use because
> of saving on-chip resources.
>
> The X-Gene SoC (ARM 64) contains 2x 10 Gbps EMACs on the chip. I have no
> idea about IOMMUs there. Thus, this platform can probably benefit of
> such driver as well. The question is whether there is some interest to
> have this kind of support in DPDK.
>
> Thus, I'd like to have the vfio/no-iommu to support the ARMv7 (otherwise
> it would be effectively dead in DPDK). Unfortunately, it's not my
> primary job at the moment.
>
> Regards
> Jan
>
> Note: as far as I know, it is discouraged to refer to lkml.org as
> it is often very slow - my case today :).
>
> On Fri, 11 Dec 2015 17:28:43 +0100
> Thomas Monjalon <thomas.monjalon at 6wind.com> wrote:
>
> > Recently there were some discussions to have an upstream replacement
> > for our igb_uio module.
> > Several solutions were discussed (new uio driver, uio_pci_generic, vfio):
> >       https://lkml.org/lkml/2015/10/16/700
> >
> > Alex Williamson (maintainer of VFIO driver), submitted a solution
> > and was waiting some feedback. Unfortunately, nobody caught it and
> > he has reverted his work:
> >
> https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/commit/?id=ae5515d
> >
> > It is an important challenge to remove our out-of-tree modules and
> > especially igb_uio. It is a long way to have a standard solution
> integrated
> > in every distributions.
> > The current cooking Linux kernel is 4.4 and will have a long term
> maintenance:
> >       https://kernel.org/releases.html
> > So it is a pity to miss this opportunity.
> >
> > Stephen has fixed a bug to use the IOMMU group zero:
> >       http://dpdk.org/browse/dpdk/commit/?id=22215f141b1
> >
> > Is there someone interested to work on VFIO no-iommu and provide
> > some feedbacks?
> > We also need to prepare a documentation patch to explain its usage
> > compared to the standard VFIO mode.
> >
> > Thanks
>
>


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