> On May 16, 2023, at 5:06 PM, Garrett D'Amore <garr...@damore.org> wrote:
>
> On May 16, 2023 at 12:19 PM -0700, Philip Prindeville
> <philipp_s...@redfish-solutions.com>, wrote:
> [snip]
>
> 3. Is "uio_pci_generic.ko" worth the potential insecurity/instability of a
> misbehaving application? My understanding is that it's only needed on SR-IOV
> hardware where MSI/MSI-X interrupts aren't supported: is there even any
> current hardware that doesn't support MSI/MSI-X? Or am I misunderstanding the
> use case?
> *Either* uio_pci_generic *or* vfio with NOIOMMU are required for the vary
> large number of systems that either lack an IOMMU (btw, that will be nearly
> all OpenWRT platforms!), or elect to run with the iommu unconfigured (one
> justification for doing that - apart from numerous software bugs and
> limitations — is that the IOMMU can slow down I/O. We actually recommend most
> of our customers that run dedicated systems run with the IOMMU disabled for
> this reason.)
>
> vfio with noiommu is preferable.
I could build with CONFIG_NOIOMMU=n and then package the modprobe .conf file
(or the grub command-line, etc) to have enable_unsafe_noiommu_mode=1, right?
This would accomplish the same thing at run-time, but allow the module to be
built to be used either with or without an IOMMU?
That's per:
https://dpdk-guide.gitlab.io/dpdk-guide/setup/binding.html
But I don't know how recent that advice is...
>
> 4. Can most functionality be achieved with VFIO + IOMMU support?
> *If* you have an IOMMU, and you aren’t trying to eke the very last bits of
> performance, yes. But as many systems don’t have an IOMMU, and as one of the
> main points of DPDK are extremely performance sensitive applications, I think
> the answer is more broadly, “no”.
> 11. What is the user-space TCP/IP stack of choice (or reference) for use with
> DPDK?
> IMO, if you’re using DPDK to run *TCP* applications then you’re probably
> misusing it — there isn’t a user land TCP stack that I would trust. IP/UDP
> is something we do, and it works well, but I can tell you already it’s a pain
> to do *just* IP, because e.g. routing tables, ARP, etc. all have to be
> handled.
> • Garrett
Yeah, good point. Are there shims to use with FRR, lldpd, et al for example?
