From: Yunsheng Lin <linyunsheng@huawei.com>
To: Mina Almasry <almasrymina@google.com>
Cc: netdev@vger.kernel.org, linux-kernel@vger.kernel.org,
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Subject: Re: [RFC PATCH net-next v6 05/15] netdev: support binding dma-buf to netdevice
Date: Thu, 7 Mar 2024 20:15:26 +0800 [thread overview]
Message-ID: <76266a89-8ec1-6a4c-716b-da422f0b2cd5@huawei.com> (raw)
In-Reply-To: <CAHS8izNJFnKGn9nrJ3kRxGwhvjiDey_bfrxQNfsfj=S9hZR_UA@mail.gmail.com>
On 2024/3/7 6:10, Mina Almasry wrote:
...
>>>>> +static int netdev_restart_rx_queue(struct net_device *dev, int rxq_idx)
>>>>> +{
>>>>> + void *new_mem;
>>>>> + void *old_mem;
>>>>> + int err;
>>>>> +
>>>>> + if (!dev || !dev->netdev_ops)
>>>>> + return -EINVAL;
>>>>> +
>>>>> + if (!dev->netdev_ops->ndo_queue_stop ||
>>>>> + !dev->netdev_ops->ndo_queue_mem_free ||
>>>>> + !dev->netdev_ops->ndo_queue_mem_alloc ||
>>>>> + !dev->netdev_ops->ndo_queue_start)
>>>>> + return -EOPNOTSUPP;
>>>>> +
>>>>> + new_mem = dev->netdev_ops->ndo_queue_mem_alloc(dev, rxq_idx);
>>>>> + if (!new_mem)
>>>>> + return -ENOMEM;
>>>>> +
>>>>> + err = dev->netdev_ops->ndo_queue_stop(dev, rxq_idx, &old_mem);
>>>>> + if (err)
>>>>> + goto err_free_new_mem;
>>>>> +
>>>>> + err = dev->netdev_ops->ndo_queue_start(dev, rxq_idx, new_mem);
>>>>> + if (err)
>>>>> + goto err_start_queue;
>>>>> +
>>>>> + dev->netdev_ops->ndo_queue_mem_free(dev, old_mem);
>>>>> +
>>>>> + return 0;
>>>>> +
>>>>> +err_start_queue:
>>>>> + dev->netdev_ops->ndo_queue_start(dev, rxq_idx, old_mem);
>>>>
>>>> It might worth mentioning why queue start with old_mem will always
>>>> success here as the return value seems to be ignored here.
>>>>
>>>
>>> So the old queue, we stopped it, and if we fail to bring up the new
>>> queue, then we want to start the old queue back up to get the queue
>>> back to a workable state.
>>>
>>> I don't see what we can do to recover if restarting the old queue
>>> fails. Seems like it should be a requirement that the driver tries as
>>> much as possible to keep the old queue restartable.
>>
>> Is it possible that we may have the 'old_mem' leaking if the driver
>> fails to restart the old queue? how does the driver handle the
>> firmware cmd failure for ndo_queue_start()? it seems a little
>> tricky to implement it.
>>
>
> I'm not sure what we can do to meaningfully recover from failure to
> restarting the old queue, except log it so the error is visible. In
> theory because we have not modifying any queue configurations
> restarting it would be straight forward, but since it's dealing with
> hardware then any failures are possible.
Yes, we may need to have a clear semantics of how should the driver
implement the above interface, for example if the driver should free
the memory when fail to start a queue or the driver should restart
the queue when fail to stop a queue? Otherwise we may have different
driver implementing different behavior.
From the disscusion you mentioned below, does it make senses to
modeling rdma subsystem by using create_queue/modify_queue/destroy_queue
semantics instead?
>
>>>
>>> I can improve this by at least logging or warning if restarting the
>>> old queue fails.
>>
>> Also the semantics of the above function seems odd that it is not
>> only restarting rx queue, but also freeing and allocating memory
>> despite the name only suggests 'restart', I am a litte afraid that
>> it may conflict with future usecae when user only need the
>> 'restart' part, perhaps rename it to a more appropriate name.
>>
>
> Oh, what we want here is just the 'restart' part. However, Jakub
> mandates that if you restart a queue (or a driver), you do it like
> this, hence the slightly more complicated implementation.
>
> https://patchwork.kernel.org/project/netdevbpf/patch/20231106024413.2801438-13-almasrymina@google.com/#25590262
> https://lore.kernel.org/netdev/20230815171638.4c057dcd@kernel.org/
Thanks for the link.
I like david's idea of "a more generic design where H/W queues are created
and destroyed - e.g., queues unique to a process which makes the cleanup
so much easier." , but it seems it is a lot of work for networking to
implement that for now.
>
next prev parent reply other threads:[~2024-03-07 12:15 UTC|newest]
Thread overview: 73+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-03-05 2:01 [RFC PATCH net-next v6 00/15] Device Memory TCP Mina Almasry
2024-03-05 2:01 ` [RFC PATCH net-next v6 01/15] queue_api: define queue api Mina Almasry
2024-03-08 1:30 ` Jakub Kicinski
2024-03-08 2:08 ` Mina Almasry
2024-03-08 3:36 ` Jakub Kicinski
2024-03-08 23:47 ` David Wei
2024-03-09 0:27 ` Mina Almasry
2024-03-11 1:12 ` David Ahern
2024-03-05 2:01 ` [RFC PATCH net-next v6 02/15] net: page_pool: create hooks for custom page providers Mina Almasry
2024-03-05 21:54 ` David Wei
2024-03-05 22:36 ` Mina Almasry
2024-03-06 14:29 ` Pavel Begunkov
2024-03-06 17:04 ` Mina Almasry
2024-03-06 19:12 ` Pavel Begunkov
2024-03-06 21:59 ` Mina Almasry
2024-03-07 14:25 ` Pavel Begunkov
2024-03-08 4:57 ` David Wei
2024-03-08 19:53 ` Mina Almasry
2024-03-18 2:02 ` Christoph Hellwig
2024-03-18 2:49 ` David Wei
2024-03-18 23:22 ` Christoph Hellwig
2024-03-22 17:40 ` Mina Almasry
2024-03-22 23:19 ` Jakub Kicinski
2024-03-24 23:35 ` Christoph Hellwig
2024-03-24 23:35 ` Christoph Hellwig
2024-03-22 17:54 ` Mina Almasry
2024-03-24 23:37 ` Christoph Hellwig
2024-03-26 20:19 ` Mina Almasry
2024-03-28 7:31 ` Christoph Hellwig
2024-04-01 19:22 ` Mina Almasry
2024-04-08 15:34 ` Cong Wang
2024-03-05 2:01 ` [RFC PATCH net-next v6 03/15] net: page_pool: factor out page_pool recycle check Mina Almasry
2024-03-05 12:55 ` Yunsheng Lin
2024-03-05 2:01 ` [RFC PATCH net-next v6 04/15] net: netdev netlink api to bind dma-buf to a net device Mina Almasry
2024-03-05 2:01 ` [RFC PATCH net-next v6 05/15] netdev: support binding dma-buf to netdevice Mina Almasry
2024-03-05 9:04 ` Arnd Bergmann
2024-03-05 20:00 ` Mina Almasry
2024-03-05 21:42 ` Arnd Bergmann
2024-03-05 12:55 ` Yunsheng Lin
2024-03-05 21:17 ` Mina Almasry
2024-03-06 12:38 ` Yunsheng Lin
2024-03-06 22:10 ` Mina Almasry
2024-03-07 12:15 ` Yunsheng Lin [this message]
2024-03-08 3:58 ` Jakub Kicinski
2024-03-05 2:01 ` [RFC PATCH net-next v6 06/15] netdev: netdevice devmem allocator Mina Almasry
2024-03-05 2:01 ` [RFC PATCH net-next v6 07/15] page_pool: convert to use netmem Mina Almasry
2024-03-05 21:30 ` Mina Almasry
2024-03-05 2:01 ` [RFC PATCH net-next v6 08/15] page_pool: devmem support Mina Almasry
2024-03-05 21:42 ` Mina Almasry
2024-03-05 2:01 ` [RFC PATCH net-next v6 09/15] memory-provider: dmabuf devmem memory provider Mina Almasry
2024-03-06 2:28 ` David Wei
2024-03-06 2:42 ` Mina Almasry
2024-03-06 2:46 ` David Wei
2024-03-06 2:54 ` Mina Almasry
2024-03-06 14:58 ` Pavel Begunkov
2024-03-06 16:51 ` Mina Almasry
2024-03-05 2:01 ` [RFC PATCH net-next v6 10/15] net: support non paged skb frags Mina Almasry
2024-03-05 2:01 ` [RFC PATCH net-next v6 11/15] net: add support for skbs with unreadable frags Mina Almasry
2024-03-05 2:01 ` [RFC PATCH net-next v6 12/15] tcp: RX path for devmem TCP Mina Almasry
2024-03-05 8:41 ` Arnd Bergmann
2024-03-05 19:22 ` Mina Almasry
2024-03-05 19:39 ` Arnd Bergmann
2024-03-05 2:01 ` [RFC PATCH net-next v6 13/15] net: add SO_DEVMEM_DONTNEED setsockopt to release RX frags Mina Almasry
2024-03-05 2:01 ` [RFC PATCH net-next v6 14/15] net: add devmem TCP documentation Mina Almasry
2024-03-08 1:52 ` Jakub Kicinski
2024-03-05 2:01 ` [RFC PATCH net-next v6 15/15] selftests: add ncdevmem, netcat for devmem TCP Mina Almasry
2024-03-05 7:16 ` [RFC PATCH net-next v6 07/15] page_pool: convert to use netmem David Howells
2024-03-05 12:54 ` [RFC PATCH net-next v6 00/15] Device Memory TCP Yunsheng Lin
2024-03-05 19:38 ` Mina Almasry
2024-03-06 12:37 ` Yunsheng Lin
2024-03-26 0:28 ` Mina Almasry
2024-03-26 12:47 ` Yunsheng Lin
2024-03-26 20:14 ` Mina Almasry
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