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

Neil Horman nhorman at tuxdriver.com
Thu Sep 1 21:15:38 CEST 2016


On Thu, Sep 01, 2016 at 10:41:22AM -0700, Stephen Hemminger wrote:
> On Thu, 1 Sep 2016 13:35:19 -0400
> Neil Horman <nhorman at tuxdriver.com> wrote:
> 
> > On Thu, Sep 01, 2016 at 12:55:27PM +0000, Trahe, Fiona wrote:
> > > Hi Neil and Olivier,
> > >   
> > > > -----Original Message-----
> > > > From: dev [mailto:dev-bounces at dpdk.org] On Behalf Of Olivier Matz
> > > > Sent: Wednesday, August 31, 2016 2:40 PM
> > > > To: Neil Horman <nhorman at tuxdriver.com>
> > > > Cc: dev at dpdk.org; thomas.monjalon at 6wind.com
> > > > Subject: Re: [dpdk-dev] [dpdk-dev, RFC] drivers: advertise kmod dependencies
> > > > in pmdinfo
> > > > 
> > > > Hi Neil,
> > > > 
> > > > On 08/31/2016 03:27 PM, Neil Horman wrote:  
> > > > > On Wed, Aug 31, 2016 at 11:21:18AM +0200, Olivier Matz wrote:  
> > > > >> 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?
> > > > >>  
> > > > > Yes, thats precisely it.  The most clear example I could think of (though I'm
> > > > > not sure if any pmd currently supports this), is a pmd that supports both UIO
> > > > > and VFIO communication with the kernel.  Such a PMD requires that one of  
> > > > those  
> > > > > two modules be loaded, but only one (i.e. both are not required), so if only  
> > > > the  
> > > > > uio kernel module loads is a success case, likewise if only the vfio module
> > > > > loads can be treated as success.  Both loading are clearly successful.  Only if
> > > > > neither load do we have a failure case.  I'm suggesting that the grammer that
> > > > > your exports define should take those cases into account.  Its not always as
> > > > > simple as "I must have the following modules"
> > > > >  
> > > > >> 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.
> > > > >>  
> > > > > If you have a human intervening in the module load process, sure, then its  
> > > > fine.  
> > > > > But it seems that this particular feature that you're implemnting might have
> > > > > automated uses.  That is to say the dpdk core library might be interested in
> > > > > parsing this particular information to direct module autoloading, and if thats
> > > > > desireable then you need to define these lists such that you can codify failure
> > > > > and success conditions.
> > > > >  
> > > > >> 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
> > > > >>  
> > > > > Oh, I see, so your list is a colon delimited list of module load sets, where at
> > > > > least one set must succeed by loading all modules in its set, but the failure of
> > > > > any one set isn't fatal to the process?  e.g. a string like this:
> > > > >
> > > > > uio,igb_uio:vfio,vfio-pci
> > > > >
> > > > > could be interpreted to mean "I must load (uio AND igb_uio) OR (vfio AND
> > > > > vfio-pci).  If the evaluation of that statement results in false, then the
> > > > > operation fails, otherwise it succedes.
> > > > >
> > > > > If thats the case, then, apologies, we're on the same page, and this will work
> > > > > just fine.  
> > > > 
> > > > Yep, that's the idea.
> > > > 
> > > > Colon and commas are the best separators I've thought about, but any
> > > > idea to make the syntax clearer is welcome ;)
> > > > 
> > > > Maybe a syntax like is clearer:
> > > >   "(mod1 & mod2)|(mod3 & mod4)" ?
> > > > But it would let the user think that more complex expressions are valid,
> > > > like "(mod1 & (mod2 | mod3)) | mod4", which is probably overkill.
> > > > 
> > > > Regards,
> > > > Olivier  
> > > 
> > > This RFC seems like a good idea - and something the Intel QuickAssist PMD could benefit from.
> > > However the (mod1 & mod2) can handle the QAT case better in my opinion.
> > > i.e.
> > > as well as needing one of 
> > > * uio igb_uio
> > > * uio uio_pci_generic
> > > * vfio vfio-pci
> > > QAT PMD also needs one of (depending on which physical device is plugged)
> > >  * qat_dh895xcc
> > >  * qat_c62x
> > >  * qat_c3xxx
> > > 
> > > So the original syntax would result in a very long list of possible variations.
> > > What really reflects the dependencies would be 
> > > ((uio & igb_uio) | (uio & uio_pci_generic) | (vfio & vfio_pci)) & (qat_dh895xcc | qat_c62x | qat_c3xxx)
> > >   
> > Ah, I didn't consider that hardware specifics might create a use case where a
> > pmd must have one or more kernel modules available for hw support.  Perhaps it
> > is worthwhile to automate hardware support - that is to say, any module loading
> > script should automatically look at the pci table exported from a pmd, and, if
> > found, load any modules that claim support for that device:vendor tuple?  Though
> > that might break in the case of uio, if there are separate driver modules that
> > support native hardware and uio access.
> 
> I ended up writing a script that went the other way.
> First look at the hardware and load VFIO if IOMMU is available.
> Then look for special driver needed for Xen and HyperV
> Lastly fallback to loading igb_uio if no VFIO and PCI device present.
> 
> In other words it is a system not driver issue.
> 
That sounds like a reasonable approach, yes.
Neil

> 


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