[RFC v3 7/7] eal: configure initial device probing

[Bruce Richardson]

On Thu, Mar 05, 2026 at 05:45:49PM +0100, David Marchand wrote:
> Some applications use port hotplug as their primary way for using DPDK
> resources.
> Having a systematic device probing is a problem when not all available
> resources will be used by the application, as such applications won't set
> an explicit allow list at startup.
> 
> This is the case for OVS on systems with multiple mlx5 devices:
> one device can be used by the kernel while the other(s) are used by DPDK.
> In such a setup, the kernel used device may get reconfigured in
> unexpected ways and trigger issues like the one described by Kevin
> not so long ago in bugzilla 1873.
> 
> Add an EAL option so that we can change the default behavior from
> block-listing to allow-listing which can be summed up as disabling
> automatic probing.
> In case some applications want to require automatic probing, add the
> opposite option.
> 
> Signed-off-by: David Marchand <david.marchand at redhat.com>
> ---
> Changes since RFC v2:
> - added -A short option alias as it seems intuitive to use with -a,
> - renamed option to --no-auto-probing (half Robin and half Thomas
>   suggestions),
> - made -A and -b conflicting options,
> - added opposite option in case an application wants an explicit behavior,
> - updated unit tests accordingly,
> - updated documentation (namely some detail on --vdev),
> 
> Changes since RFC v1:
> - changed approach following Bruce suggestion,
> 
> ---
>  app/test/test_eal_flags.c                 | 63 +++++++++++++++++++++++
>  devtools/test-null.sh                     |  2 +-
>  doc/guides/linux_gsg/eal_args.include.rst | 13 +++++
>  lib/eal/common/eal_common_bus.c           | 17 +++---
>  lib/eal/common/eal_common_options.c       | 10 ++++
>  lib/eal/common/eal_internal_cfg.h         |  1 +
>  lib/eal/common/eal_option_list.h          |  2 +
>  7 files changed, 101 insertions(+), 7 deletions(-)
> 

While I really like "-A" as a logical shortcut, I am a little concerned it
doesn't seem a shortcut for "--no-auto-probing". However, I don't have a
better suggestion so.

Acked-by: Bruce Richardson <bruce.richardson at intel.com>