Re: VFIO no-iommu

[Vincent JARDIN <vincent.jardin@6wind.com>]

Thanks Thomas for putting back this topic.

Alex,

I'd like to hear more about the impacts of "unsupported":
https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/commit/?id=033291eccbdb1b70ffc02641edae19ac825dc75d
   Use of this mode, specifically binding a device without a native
   IOMMU group to a VFIO bus driver will taint the kernel and should
   therefore not be considered supported.

It means that we get ride of uio; so it is a nice code cleanup: but why 
would VFIO/NO IOMMU be better if the bottomline is "unsupported"?

Thank you,
   Vincent

On 11/12/2015 17:28, Thomas Monjalon 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
>