Re: [dpdk-dev] [PATCH 1/2] doc: Update GSG for uio_pci_generic use

[Bruce Richardson <bruce.richardson@intel.com>]

On Wed, Feb 25, 2015 at 12:14:15PM +0000, Iremonger, Bernard wrote:
> 
> 
> > -----Original Message-----
> > From: dev [mailto:dev-bounces@dpdk.org] On Behalf Of Bruce Richardson
> > Sent: Tuesday, February 24, 2015 4:28 PM
> > To: dev@dpdk.org
> > Subject: [dpdk-dev] [PATCH 1/2] doc: Update GSG for uio_pci_generic use
> > 
> > Since DPDK now has support for the in-tree uio_pci_generic driver, update the GSG document to
> > reference this module, and to use it in preference to the igb_uio driver, which is DPDK-specific.
> > 
> > Signed-off-by: Bruce Richardson <bruce.richardson@intel.com>
> > ---
> >  doc/guides/linux_gsg/build_dpdk.rst        | 63 +++++++++++++++++-------------
> >  doc/guides/linux_gsg/build_sample_apps.rst |  5 ++-
> >  doc/guides/linux_gsg/enable_func.rst       |  2 +
> >  3 files changed, 40 insertions(+), 30 deletions(-)
> > 
> > diff --git a/doc/guides/linux_gsg/build_dpdk.rst b/doc/guides/linux_gsg/build_dpdk.rst
> > index d09c69d..255d6dc 100644
> > --- a/doc/guides/linux_gsg/build_dpdk.rst
> > +++ b/doc/guides/linux_gsg/build_dpdk.rst
> > @@ -133,7 +133,8 @@ use the make config T=<target> command:
> > 
> >  .. warning::
> > 
> > -    The igb_uio module must be compiled with the same kernel as the one running on the target.
> > +    Any kernel modules to be used, e.g. igb_uio, kni, must be compiled with the
> > +    same kernel as the one running on the target.
> >      If the DPDK is not being built on the target machine,
> >      the RTE_KERNELDIR environment variable should be used to point the compilation at a copy of the
> > kernel version to be used on the target machine.
> > 
> > @@ -154,28 +155,29 @@ Browsing the Installed DPDK Environment Target
> > 
> >  Once a target is created it contains all libraries and header files for the DPDK environment that are
> > required to build customer applications.
> >  In addition, the test and testpmd applications are built under the build/app directory, which may be
> > used for testing.
> > -In the case of Linux, a kmod  directory is also present that contains a module to install:
> > +A kmod  directory is also present that contains kernel modules which may be loaded if needed:
> > 
> >  .. code-block:: console
> > 
> >      $ ls x86_64-native-linuxapp-gcc
> >      app build hostapp include kmod lib Makefile
> > 
> > -Loading the DPDK igb_uio Module
> > --------------------------------
> > +Loading Modules to Enable Userspace IO for DPDK
> > +-----------------------------------------------
> > 
> > -To run any DPDK application, the igb_uio module can be loaded into the running kernel.
> > -The module is found in the kmod sub-directory of the DPDK target directory.
> > -This module should be loaded using the insmod command as shown below (assuming that the
> > current directory is the DPDK target directory).
> > -In many cases, the uio support in the Linux* kernel is compiled as a module rather than as part of the
> > kernel, -so it is often necessary to load the uio module first:
> 
> 
> Hi Bruce,
> 
> Should the information about igb_uio be retained alongside the new information about uio_pci_generic?
>  

This is obviously a matter of opinion, but: "no".
This doc is a Getting Started Guide, and therefore meant to cover just the minimum
needed to get up and running and ignoring advanced details. 
"uio_pci_generic" is the simplest path to getting up and running quickly, and
maintaining mention of igb_uio just adds to the complexity of the documentation.

Since uio_pci_generic also works on most linux distro's I'd also be tempted to
move the vfio details out of the main GSG body - perhaps to the extra chapter
covering KNI and running as non-root, again with the objective of simplifying
things for the beginner. VFIO and igb_uio are provided for those who want something
extra above what uio_pci_generic provides, e.g. security, or ability to create
VF devices on all kernels while having the PF in use by DPDK.

Regards,
/Bruce