Re: [dpdk-dev] kernel binding of devices + hotplug

["Wiles, Keith" <keith.wiles@intel.com>]

On Apr 13, 2018, at 11:40 AM, Bruce Richardson <bruce.richardson@intel.com<mailto:bruce.richardson@intel.com>> wrote:

On Fri, Apr 13, 2018 at 06:31:21PM +0200, Thomas Monjalon wrote:
It's time to think (again) how we bind devices with kernel modules.
We need to decide how we want to manage hotplugged devices with DPDK.

A bit of history first.
There was some code in DPDK for bind/unbind, but it has been removed
in DPDK 1.7 - http://dpdk.org/commit/5d8751b83
Copy of the commit message (in 2014):
"
The bind/unbind operations should not be handled by the eal.
These operations should be either done outside of dpdk or
inside the PMDs themselves as these are their problems.
"

The question raised at this time (4 years ago) is still under discussion.
Should we manage binding inside or outside DPDK?
Should it be controlled in the application or in the OS base?

As you know, we use dpdk-devbind.py.
This tool lacks two major features:
- persistent configuration
- hotplug

If we consider that the DPDK applications should be able to apply its own
policy to choose the devices to bind, then we need to implement binding
in the PMD (with EAL helpers).

On the other hand, if we consider that it is the system responsibility,
then we could choose systemd/udev and driverctl.

The debate is launched!


Allow me to nail my colours to the mast early! :-)

I believe it's system not application responsibility.
I also believe I have previously explained my reasons for that choice in
some of the previous email threads.

I agree the system should be handling hot-plug and device bindings as the sys-admin or orchestration layer would be handling what device appears/disappears plus which are accessible by an application. Now an application would need to know when a device appears/disappears, which should be handled by the current hot-plug support (I assume).


/Bruce

Regards,
Keith