netdev - Re: [PATCH RFC net-next 7/7] netdevsim: Add simple FIB resource controller via devlink

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Date:   Sat, 24 Mar 2018 08:26:21 +0100
From:   Jiri Pirko <jiri@...nulli.us>
To:     David Ahern <dsa@...ulusnetworks.com>
Cc:     netdev@...r.kernel.org, davem@...emloft.net,
        roopa@...ulusnetworks.com, shm@...ulusnetworks.com,
        jiri@...lanox.com, idosch@...lanox.com,
        jakub.kicinski@...ronome.com, David Ahern <dsahern@...il.com>
Subject: Re: [PATCH RFC net-next 7/7] netdevsim: Add simple FIB resource
 controller via devlink

Fri, Mar 23, 2018 at 04:13:14PM CET, dsa@...ulusnetworks.com wrote:
>On 3/23/18 9:05 AM, Jiri Pirko wrote:
>> Fri, Mar 23, 2018 at 04:03:40PM CET, dsa@...ulusnetworks.com wrote:
>>> On 3/23/18 9:01 AM, Jiri Pirko wrote:
>>>> Fri, Mar 23, 2018 at 03:31:02PM CET, dsa@...ulusnetworks.com wrote:
>>>>> On 3/23/18 12:50 AM, Jiri Pirko wrote:
>>>>>>> +void nsim_devlink_setup(struct netdevsim *ns)
>>>>>>> +{
>>>>>>> +	struct net *net = dev_net(ns->netdev);
>>>>>>> +	bool *reg_devlink = net_generic(net, nsim_devlink_id);
>>>>>>> +	struct devlink *devlink;
>>>>>>> +	int err = -ENOMEM;
>>>>>>> +
>>>>>>> +	/* only one device per namespace controls devlink */
>>>>>>> +	if (!*reg_devlink) {
>>>>>>> +		ns->devlink = NULL;
>>>>>>> +		return;
>>>>>>> +	}
>>>>>>> +
>>>>>>> +	devlink = devlink_alloc(&nsim_devlink_ops, 0);
>>>>>>> +	if (!devlink)
>>>>>>> +		return;
>>>>>>> +
>>>>>>> +	devlink_net_set(devlink, net);
>>>>>>> +	err = devlink_register(devlink, &ns->dev);
>>>>>>
>>>>>> This reg_devlink construct looks odd. Why don't you leave the devlink
>>>>>> instance in init_ns?
>>>>>
>>>>> It is a per-network namespace resource controller. Since struct devlink
>>>>
>>>> Wait a second. What do you mean by "per-network namespace"? Devlink
>>>> instance is always associated with one physical device. Like an ASIC.
>>>>
>>>>
>>>>> has a net entry, the simplest design is to put it into the namespace of
>>>>> the controller. Without it, controlling resource sizes in namespace
>>>>> 'foobar' has to be done from init_net, which is just wrong.
>>>
>>> you need to look at how netdevsim creates a device per netdevice.
>> 
>> That means one devlink instance for each netdevsim device, doesn't it?
>> 
>
>yes.

Still not sure how to handle namespaces in devlink. Originally, I
thought it would be okay to leave all devlink instances in init_ns.
Because what happens if you move netdev to another namespace? Should the
devlink move as well? What if you have multiple ports, each in different
namespace. Can user move devlink instance to another namespace? Etc.