I think the latest and greatest ATOMs have iommu support. On Tue, Jan 24, 2017 at 11:05 PM, Burt Silverman <bur...@gmail.com> wrote:
> Hi Damjan, > > My understanding is that CONFIG_VFIO_NOIOMMU will never be set in a stock > kernel, and you will need to build a custom kernel for that. I understand > that with this option, the kernel cannot guarantee that applications are > prevented from creating bugs that normally the kernel can guarantee will > not occur (outside of a kernel bug.) It therefore violates the fundamental > Linux system design. That being said, you may wish to accept the risk for > performance reasons and build a custom kernel. The other strange thing > would be that MSI or MSI-X style interrupts are not needed for performance. > The people who developed them have made a lot of noise about how they came > about for performance reasons. I have no direct experience, but to learn > that they are not important is a shock. > > It seems to me that the Ubuntu 14.04 issue is really a separate one from > all of this, although I would imagine that the conclusion to stop > supporting it does not change. > > Burt > > On Tue, Jan 24, 2017 at 1:07 PM, Damjan Marion (damarion) < > damar...@cisco.com> wrote: > >> >> > On 24 Jan 2017, at 18:40, Damjan Marion (damarion) <damar...@cisco.com> >> wrote: >> > >> >> >> >> On 24 Jan 2017, at 18:26, Stephen Hemminger < >> step...@networkplumber.org> wrote: >> >> >> >> On Tue, 24 Jan 2017 17:14:42 +0000 >> >> "Damjan Marion (damarion)" <damar...@cisco.com> wrote: >> >> >> >>> Is anybody aware of any valid reason why we cannot switch to >> uio_pci_generic >> >>> as default PCI uio driver in ubuntu packages? >> >>> >> >>> I think generally people don’t like out-of-tree modules, so as long >> as we are getting >> >>> the same service from uio_pci_generic we should use it… >> >>> >> >>> Thanks, >> >>> >> >>> Damjan >> > >> >> uio_pci_generic does not support MSI or MSI-X interrupts, only legacy >> INTX. >> > >> > I know but do we really care? >> > >> >> >> >> The preference should always be to use VFIO. Even on systems without >> IOMMU. >> > >> > What is the perf impact? >> > >> > Also, I just tried with kernel 4.8 on rangeley ATOM, and i got: >> > >> > [536030.250072] vfio-pci: probe of 0000:00:14.0 failed with error -22 >> > [536030.253271] vfio-pci: probe of 0000:00:14.0 failed with error -22 >> > >> > I guess I’m doing something wrong…. >> >> This explains: >> >> grep VFIO_NOIO /boot/config-4.8.0-34-generic >> # CONFIG_VFIO_NOIOMMU is not set >> >> So vfio is out of the game of being default choice, people can still >> switch simply with one line change in /etc/vpp/startup.conf. >> >> >> _______________________________________________ >> vpp-dev mailing list >> vpp-dev@lists.fd.io >> https://lists.fd.io/mailman/listinfo/vpp-dev >> > >
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