Re: [dpdk-dev] VFIO no-iommu

[Thomas Monjalon <thomas.monjalon@6wind.com>]

2015-12-16 16:23, Burakov, Anatoly:
> Hi Thomas,
> 
>  > > On Tue, Dec 15, 2015 at 09:53:18AM -0700, Alex Williamson wrote:
> > > So it works.  Is it acceptable?  Useful?  Sufficiently complete?  Does
> > > it imply deprecating the uio interface?  I believe the feature that
> > > started this discussion was support for MSI/X interrupts so that VFs
> > > can support some kind of interrupt (uio only supports INTx since it
> > > doesn't allow DMA).  Implementing that would be the ultimate test of
> > > whether this provides dpdk with not only a more consistent interface,
> > > but the feature dpdk wants that's missing in uio. Thanks,
> 
> Ferruh has done a great job so far testing Alex's patch, very few changes from DPDK side seem to be required as far as existing functionality goes (not sure about VF interrupts mentioned by Alex). However, one thing that concerns me is usability. While it is true that no-IOMMU mode in VFIO would mean uio interfaces could be deprecated in time, the no-iommu mode is way more hassle than using igb_uio/uio_pci_generic because it will require a kernel recompile as opposed to simply compiling and insmod'ding an out-of-tree driver. So, in essence, if you don't want an IOMMU, it's becoming that much harder to use DPDK. Would that be something DPDK is willing to live with in the absence of uio interfaces?

Excuse me if I missed something obvious.
Why a kernel compilation is needed?