linux-kernel - Re: [RFC PATCH net-next v6 09/15] memory-provider: dmabuf devmem memory provider

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Date: Wed, 6 Mar 2024 14:58:38 +0000
From: Pavel Begunkov <asml.silence@...il.com>
To: Mina Almasry <almasrymina@...gle.com>, David Wei <dw@...idwei.uk>
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Subject: Re: [RFC PATCH net-next v6 09/15] memory-provider: dmabuf devmem
 memory provider

On 3/6/24 02:42, Mina Almasry wrote:
> On Tue, Mar 5, 2024 at 6:28 PM David Wei <dw@...idwei.uk> wrote:
>>
>> On 2024-03-04 18:01, Mina Almasry wrote:
>>> +     if (pool->p.queue)
>>> +             binding = READ_ONCE(pool->p.queue->binding);
>>> +
>>> +     if (binding) {
>>> +             pool->mp_ops = &dmabuf_devmem_ops;
>>> +             pool->mp_priv = binding;
>>> +     }
>>
>> This is specific to TCP devmem. For ZC Rx we will need something more
>> generic to let us pass our own memory provider backend down to the page
>> pool.
>>
>> What about storing ops and priv void ptr in struct netdev_rx_queue
>> instead? Then we can both use it.
> 
> Yes, this is dmabuf specific, I was thinking you'd define your own
> member of netdev_rx_queue, and then add something like this to
> page_pool_init:

That would be quite annoying, there are 3 expected users together
with huge pages, each would need a field and check all others are
disabled as you mentioned and so on. It should be cleaner to pass
a generic {pp_ops,pp_private} pair instead.

If header dependencies is a problem, you it can probably be

struct pp_provider_param {
	struct pp_ops ops;
	void *private;
};

# netdev_rx_queue.h

// definition is not included here
struct pp_provider_params;

struct netdev_rx_queue {
	...
	struct pp_provider_params *pp_params;
};

-- 
Pavel Begunkov