[dpdk-dev] [PATCH v2 1/2] vfio: fix build if build envrionment is on old kernel

Thomas Monjalon thomas.monjalon at 6wind.com
Fri Jul 10 22:19:58 CEST 2015


2015-07-10 10:29, Stephen Hemminger:
> On Fri, 10 Jul 2015 01:43:17 +0200
> Thomas Monjalon <thomas.monjalon at 6wind.com> wrote:
> 
> > 2015-07-09 16:26, Stephen Hemminger:
> > > From: Stephen Hemminger <shemming at brocade.com>
> > > 
> > > The build of DPDK may be done on a system where Linux headers
> > > in /usr/include (and therefore kernel version macro) are much
> > > older than the target runtime system.
> > 
> > It seems strange wanting to build a feature not present in the kernel
> > headers. Why not upgrading the build system kernel?
> 
> The build machine is running Debian with stock headers and kernel.
> I can see many people having build environments controlled by other
> parts of organization where you are not allowed to update packages.
> 
> > > In order to work around this, one solution is to put in simplified
> > > kernel header (this is what the compat stuff is already doing).
> > 
> > The other solution (as already suggested by Anatoly) is to have a configure
> > script (not an autotool one). It would make clear that VFIO support is not
> > built.
> > Ref: http://dpdk.org/ml/archives/dev/2015-April/016772.html
> 
> That won't solve the issue.

That allows to see the error earlier and more clearly.

> The other possiblities are:
>  1. Fail the build if VFIO is configured but headers files are missing.
>     This is better than surprising user at runtime.
>  2. Don't use /usr/include/linux as path as expected path of kernel headers
>     instead use build path (this is what modules do).

The latter one seems to be the right one. There is a name for that technique:
cross-compilation. If you want to build DPDK to run on another system with
different kernel and libraries, you should adapt the toolchain and libraries
headers. And guess what? include/linux/ is part of this toolchain.
Problem solved.


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