[dpdk-dev] What to do about UIO breakage in 2.0

[dpdk-dev] What to do about UIO breakage in 2.0

[Stephen Hemminger]

I raised the issue, but people seem to be ignoring that fact that igb_uio
was broken by the introduction of UIO PCI generic in 2.0.

There are three options:
 1. Remove IGB_UIO only use UIO PCI generic.
    Downside there is no MSI-X support for UIO PCI generic.
 2. Revert UIO PCI generic support
 3. Replace both of the above with something better.

I am working on #3 but it will not be ready for 2.0.1 and there
is no solution for users of 2.0 and any future stable code.

Re: [dpdk-dev] What to do about UIO breakage in 2.0

[Matthew Hall]

Stephen,

This mail is a bit confusing for end users of DPDK which might be why you didn't get many replies yet.

If I understand this mail right, you're saying that nothing works? Or it works, but igb_uio doesn't work, and the performance isn't good because MSI-X is not working? I am confused what you're saying exactly.

Previously I think we knew we needed to use igb_uio for almost all the non-virtual NIC PMDs, and some of the virtual NIC PMDs also, before they would load and get access to the PCIe BARs, etc. for the NICs. But now it sounds totally changed so I'm not sure what to reply.

Can you give a use case, from the perspective of the guy trying to bootstrap EAL / DPDK, what does this problem do to him if he tries it with DPDK 2.X?

Matthew.

On Apr 27, 2015, at 3:06 PM, Stephen Hemminger <stephen@networkplumber.org> wrote:

> I raised the issue, but people seem to be ignoring that fact that igb_uio
> was broken by the introduction of UIO PCI generic in 2.0.
> 
> There are three options:
> 1. Remove IGB_UIO only use UIO PCI generic.
>    Downside there is no MSI-X support for UIO PCI generic.
> 2. Revert UIO PCI generic support
> 3. Replace both of the above with something better.
> 
> I am working on #3 but it will not be ready for 2.0.1 and there
> is no solution for users of 2.0 and any future stable code.

Re: [dpdk-dev] What to do about UIO breakage in 2.0

[Qiu, Michael]

On 4/28/2015 6:06 AM, Stephen Hemminger wrote:
> I raised the issue, but people seem to be ignoring that fact that igb_uio
> was broken by the introduction of UIO PCI generic in 2.0.

What do you mean about igb_uio broken?

Thanks,
Michael
>
> There are three options:
>  1. Remove IGB_UIO only use UIO PCI generic.
>     Downside there is no MSI-X support for UIO PCI generic.
>  2. Revert UIO PCI generic support
>  3. Replace both of the above with something better.
>
> I am working on #3 but it will not be ready for 2.0.1 and there
> is no solution for users of 2.0 and any future stable code.
>

Re: [dpdk-dev] What to do about UIO breakage in 2.0

[Stephen Hemminger]

On Tue, 28 Apr 2015 08:07:18 +0000
"Qiu, Michael" <michael.qiu@intel.com> wrote:

> On 4/28/2015 6:06 AM, Stephen Hemminger wrote:
> > I raised the issue, but people seem to be ignoring that fact that igb_uio
> > was broken by the introduction of UIO PCI generic in 2.0.
> 
> What do you mean about igb_uio broken?
> 
> Thanks,
> Michael
> >
> > There are three options:
> >  1. Remove IGB_UIO only use UIO PCI generic.
> >     Downside there is no MSI-X support for UIO PCI generic.
> >  2. Revert UIO PCI generic support
> >  3. Replace both of the above with something better.
> >
> > I am working on #3 but it will not be ready for 2.0.1 and there
> > is no solution for users of 2.0 and any future stable code.
> >
> 

If you use link state interrupt, then the base code in eal_interrupts
is now broken when using igb_uio. The code was changed to work with
uio_pci_generic. The new code does read/write of PCI INTX config and
will not work when using igb_uio which uses MSI-X.

Some possible solutions are:
 1. Remove igb_uio completely 
 2. Revert/remove uio_pci_generic and use old read/write to enable irq
 3. Make code look at driver type (sending patches for that now).
 4. Implement a better UIO method for MSI-X which is what I will submit
    when Rx IRQ support is ready.