[dpdk-dev] [dpdk-dev, RFC] drivers: advertise kmod dependencies in pmdinfo

[Olivier Matz]

Hi Neil,

On 08/30/2016 03:23 PM, Neil Horman wrote:
> On Fri, Aug 26, 2016 at 03:20:46PM +0200, Olivier Matz wrote:
>> Add a new macro DRIVER_REGISTER_KMOD_DEP() that allows a driver to
>> declare the list of kernel modules required to run properly.
>>
>> Today, most PCI drivers require uio/vfio.
>>
>> Signed-off-by: Olivier Matz <olivier.matz at 6wind.com>
>>
>> ---
>> In this RFC, I supposed that all PCI drivers require a the loading of a
>> uio/vfio module (except mlx*), this may be wrong.
>> Comments are welcome!
>>
>>
>>  buildtools/pmdinfogen/pmdinfogen.c      |  1 +
>>  buildtools/pmdinfogen/pmdinfogen.h      |  1 +
>>  drivers/crypto/qat/rte_qat_cryptodev.c  |  2 ++
>>  drivers/net/bnx2x/bnx2x_ethdev.c        |  4 ++++
>>  drivers/net/bnxt/bnxt_ethdev.c          |  2 ++
>>  drivers/net/cxgbe/cxgbe_ethdev.c        |  2 ++
>>  drivers/net/e1000/em_ethdev.c           |  2 ++
>>  drivers/net/e1000/igb_ethdev.c          |  4 ++++
>>  drivers/net/ena/ena_ethdev.c            |  2 ++
>>  drivers/net/enic/enic_ethdev.c          |  2 ++
>>  drivers/net/fm10k/fm10k_ethdev.c        |  2 ++
>>  drivers/net/i40e/i40e_ethdev.c          |  2 ++
>>  drivers/net/i40e/i40e_ethdev_vf.c       |  2 ++
>>  drivers/net/ixgbe/ixgbe_ethdev.c        |  4 ++++
>>  drivers/net/mlx4/mlx4.c                 |  2 ++
>>  drivers/net/mlx5/mlx5.c                 |  3 +++
>>  drivers/net/nfp/nfp_net.c               |  2 ++
>>  drivers/net/qede/qede_ethdev.c          |  4 ++++
>>  drivers/net/szedata2/rte_eth_szedata2.c |  2 ++
>>  drivers/net/thunderx/nicvf_ethdev.c     |  2 ++
>>  drivers/net/virtio/virtio_ethdev.c      |  2 ++
>>  drivers/net/vmxnet3/vmxnet3_ethdev.c    |  2 ++
>>  lib/librte_eal/common/include/rte_dev.h | 14 ++++++++++++++
>>  tools/dpdk-pmdinfo.py                   |  5 ++++-
>>  24 files changed, 69 insertions(+), 1 deletion(-)
>>
> 
> Generally speaking, I like the idea, it makes sense to me in terms of using
> pmdinfo to export this information
> 
> That said, This may need to be a set of macros.  By that I mean (and correct me
> if I'm wrong here), but the relationship between pmd's and kernel modules is in
> some cases, more complex than a 'requires' or 'depends' relationship.  That is
> to say, some pmd may need user space hardware access, but can use either uio OR
> vfio, but doesn't need both, and can continue to function if only one is
> available.  Other PMD's may be able to use vfio or uio, but can still function
> without either.  And some, as your patch implements, simply require one or the
> other to function.  As such it seems like you may want a few macros, in the form
> of:
> 
> DRIVER_REGISTER_KMOD_REQUEST - List of modules to attempt loading, ignore any
> failures 
> DRIVER_REGISTER_KMOD_REQUIRE - List of modules required to be loaded after
> request macro completes, fail if any are not loaded
> 
> Thats just spitballing, mind you, theres probably a better way to do it, but the
> idea is to list a set of modules you would like to have, and then create a
> parsable syntax to describe the modules that need to be loaded after the request
> is complete so that you can accurately codify the situations I described above.

Thank you for your feedback.
However, I'm not sure I'm perfectly getting what you suggest.

Do you think some PMDs could request a kernel module without really
requiring it? Do you have an example in mind?

The syntax I've submitted lets you define several lists of modules, so
that the user or the script that starts the application can decide which
kmod list is better according to the environment.

For example, most drivers will advertise
"uio,igb_uio:uio,uio_pci_generic:vfio,vfio-pci", and the user or script
will have to choose between loading:
- uio igb_uio
- uio uio_pci_generic
- vfio vfio-pci


Olivier