Subject: Re: [PATCH v7 13/15] io_uring/zcrx: set pp memory provider for an rx queue

From: Jens Axboe <[email-masked]>
Date: Fri, 1 Nov 2024 14:35:25 -0600

On 11/1/24 2:16 PM, Mina Almasry wrote:
> On Tue, Oct 29, 2024 at 4:06?PM David Wei <[email-masked]> wrote:
>>
>> From: David Wei <[email-masked]>
>>
>> Set the page pool memory provider for the rx queue configured for zero
>> copy to io_uring. Then the rx queue is reset using
>> netdev_rx_queue_restart() and netdev core + page pool will take care of
>> filling the rx queue from the io_uring zero copy memory provider.
>>
>> For now, there is only one ifq so its destruction happens implicitly
>> during io_uring cleanup.
>>
>> Signed-off-by: David Wei <[email-masked]>
>> ---
>>  io_uring/zcrx.c | 86 +++++++++++++++++++++++++++++++++++++++++++++++--
>>  io_uring/zcrx.h |  2 ++
>>  2 files changed, 86 insertions(+), 2 deletions(-)
>>
>> diff --git a/io_uring/zcrx.c b/io_uring/zcrx.c
>> index 477b0d1b7b91..3f4625730dbd 100644
>> --- a/io_uring/zcrx.c
>> +++ b/io_uring/zcrx.c
>> @@ -8,6 +8,7 @@
>>  #include <net/page_pool/helpers.h>
>>  #include <net/page_pool/memory_provider.h>
>>  #include <trace/events/page_pool.h>
>> +#include <net/netdev_rx_queue.h>
>>  #include <net/tcp.h>
>>  #include <net/rps.h>
>>
>> @@ -36,6 +37,65 @@ static inline struct io_zcrx_area *io_zcrx_iov_to_area(const struct net_iov *nio
>>         return container_of(owner, struct io_zcrx_area, nia);
>>  }
>>
>> +static int io_open_zc_rxq(struct io_zcrx_ifq *ifq, unsigned ifq_idx)
>> +{
>> +       struct netdev_rx_queue *rxq;
>> +       struct net_device *dev = ifq->dev;
>> +       int ret;
>> +
>> +       ASSERT_RTNL();
>> +
>> +       if (ifq_idx >= dev->num_rx_queues)
>> +               return -EINVAL;
>> +       ifq_idx = array_index_nospec(ifq_idx, dev->num_rx_queues);
>> +
>> +       rxq = __netif_get_rx_queue(ifq->dev, ifq_idx);
>> +       if (rxq->mp_params.mp_priv)
>> +               return -EEXIST;
>> +
>> +       ifq->if_rxq = ifq_idx;
>> +       rxq->mp_params.mp_ops = &io_uring_pp_zc_ops;
>> +       rxq->mp_params.mp_priv = ifq;
>> +       ret = netdev_rx_queue_restart(ifq->dev, ifq->if_rxq);
>> +       if (ret)
>> +               goto fail;
>> +       return 0;
>> +fail:
>> +       rxq->mp_params.mp_ops = NULL;
>> +       rxq->mp_params.mp_priv = NULL;
>> +       ifq->if_rxq = -1;
>> +       return ret;
>> +}
>> +
> 
> I don't see a CAP_NET_ADMIN check. Likely I missed it. Is that done
> somewhere? Binding user memory to an rx queue needs to be a privileged
> operation.

There's only one caller of this, and it literally has a CAP_NET_ADMIN at
the very top. Patch 9 adds the registration.

-- 
Jens Axboe