From: Simon Horman <horms@kernel.org>
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 v7 04/14] netdev: support binding dma-buf to netdevice
Date: Thu, 28 Mar 2024 20:38:08 +0000 [thread overview]
Message-ID: <20240328203808.GL651713@kernel.org> (raw)
In-Reply-To: <CAHS8izMZuRwQZsL7PQdoRcrgeh6rEa7n1NMhbm-aZMes2QHVzg@mail.gmail.com>
On Thu, Mar 28, 2024 at 11:55:23AM -0700, Mina Almasry wrote:
> On Thu, Mar 28, 2024 at 11:28 AM Simon Horman <horms@kernel.org> wrote:
> >
> > On Tue, Mar 26, 2024 at 03:50:35PM -0700, Mina Almasry wrote:
> > > Add a netdev_dmabuf_binding struct which represents the
> > > dma-buf-to-netdevice binding. The netlink API will bind the dma-buf to
> > > rx queues on the netdevice. On the binding, the dma_buf_attach
> > > & dma_buf_map_attachment will occur. The entries in the sg_table from
> > > mapping will be inserted into a genpool to make it ready
> > > for allocation.
> > >
> > > The chunks in the genpool are owned by a dmabuf_chunk_owner struct which
> > > holds the dma-buf offset of the base of the chunk and the dma_addr of
> > > the chunk. Both are needed to use allocations that come from this chunk.
> > >
> > > We create a new type that represents an allocation from the genpool:
> > > net_iov. We setup the net_iov allocation size in the
> > > genpool to PAGE_SIZE for simplicity: to match the PAGE_SIZE normally
> > > allocated by the page pool and given to the drivers.
> > >
> > > The user can unbind the dmabuf from the netdevice by closing the netlink
> > > socket that established the binding. We do this so that the binding is
> > > automatically unbound even if the userspace process crashes.
> > >
> > > The binding and unbinding leaves an indicator in struct netdev_rx_queue
> > > that the given queue is bound, but the binding doesn't take effect until
> > > the driver actually reconfigures its queues, and re-initializes its page
> > > pool.
> > >
> > > The netdev_dmabuf_binding struct is refcounted, and releases its
> > > resources only when all the refs are released.
> > >
> > > Signed-off-by: Willem de Bruijn <willemb@google.com>
> > > Signed-off-by: Kaiyuan Zhang <kaiyuanz@google.com>
> > > Signed-off-by: Mina Almasry <almasrymina@google.com>
> >
> > ...
> >
> > > +int net_devmem_bind_dmabuf_to_queue(struct net_device *dev, u32 rxq_idx,
> > > + struct net_devmem_dmabuf_binding *binding)
> > > +{
> > > + struct netdev_rx_queue *rxq;
> > > + u32 xa_idx;
> > > + int err;
> > > +
> > > + if (rxq_idx >= dev->num_rx_queues)
> > > + return -ERANGE;
> > > +
> > > + rxq = __netif_get_rx_queue(dev, rxq_idx);
> > > + if (rxq->mp_params.mp_priv)
> > > + return -EEXIST;
> > > +
> > > + err = xa_alloc(&binding->bound_rxq_list, &xa_idx, rxq, xa_limit_32b,
> > > + GFP_KERNEL);
> > > + if (err)
> > > + return err;
> > > +
> > > + /* We hold the rtnl_lock while binding/unbinding dma-buf, so we can't
> > > + * race with another thread that is also modifying this value. However,
> > > + * the driver may read this config while it's creating its * rx-queues.
> > > + * WRITE_ONCE() here to match the READ_ONCE() in the driver.
> > > + */
> > > + WRITE_ONCE(rxq->mp_params.mp_ops, &dmabuf_devmem_ops);
> >
> > Hi Mina,
> >
> > This causes a build failure because mabuf_devmem_ops is not added until a
> > subsequent patch in this series.
> >
>
> My apologies. I do notice the failure in patchwork now. I'll do a
> patch by patch build for the next iteration.
Thanks, much appreciated.
> > > + WRITE_ONCE(rxq->mp_params.mp_priv, binding);
> > > +
> > > + err = net_devmem_restart_rx_queue(dev, rxq_idx);
> > > + if (err)
> > > + goto err_xa_erase;
> > > +
> > > + return 0;
> > > +
> > > +err_xa_erase:
> > > + WRITE_ONCE(rxq->mp_params.mp_ops, NULL);
> > > + WRITE_ONCE(rxq->mp_params.mp_priv, NULL);
> > > + xa_erase(&binding->bound_rxq_list, xa_idx);
> > > +
> > > + return err;
> > > +}
> >
> > ...
>
>
>
> --
> Thanks,
> Mina
>
next prev parent reply other threads:[~2024-03-28 20:38 UTC|newest]
Thread overview: 21+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-03-26 22:50 [RFC PATCH net-next v7 00/14] Device Memory TCP Mina Almasry
2024-03-26 22:50 ` [RFC PATCH net-next v7 01/14] queue_api: define queue api Mina Almasry
2024-03-26 22:50 ` [RFC PATCH net-next v7 02/14] net: page_pool: create hooks for custom page providers Mina Almasry
2024-03-26 22:50 ` [RFC PATCH net-next v7 03/14] net: netdev netlink api to bind dma-buf to a net device Mina Almasry
2024-03-26 22:50 ` [RFC PATCH net-next v7 04/14] netdev: support binding dma-buf to netdevice Mina Almasry
2024-03-28 18:28 ` Simon Horman
2024-03-28 18:55 ` Mina Almasry
2024-03-28 20:38 ` Simon Horman [this message]
2024-03-26 22:50 ` [RFC PATCH net-next v7 05/14] netdev: netdevice devmem allocator Mina Almasry
2024-03-26 22:50 ` [RFC PATCH net-next v7 06/14] page_pool: convert to use netmem Mina Almasry
2024-03-27 8:25 ` Mina Almasry
2024-03-26 22:50 ` [RFC PATCH net-next v7 07/14] page_pool: devmem support Mina Almasry
2024-03-27 8:26 ` Mina Almasry
2024-03-26 22:50 ` [RFC PATCH net-next v7 08/14] memory-provider: dmabuf devmem memory provider Mina Almasry
2024-03-26 22:50 ` [RFC PATCH net-next v7 09/14] net: support non paged skb frags Mina Almasry
2024-03-26 22:50 ` [RFC PATCH net-next v7 10/14] net: add support for skbs with unreadable frags Mina Almasry
2024-03-26 22:50 ` [RFC PATCH net-next v7 11/14] tcp: RX path for devmem TCP Mina Almasry
2024-03-26 22:50 ` [RFC PATCH net-next v7 12/14] net: add SO_DEVMEM_DONTNEED setsockopt to release RX frags Mina Almasry
2024-03-26 22:50 ` [RFC PATCH net-next v7 13/14] net: add devmem TCP documentation Mina Almasry
2024-03-27 0:38 ` Randy Dunlap
2024-03-26 22:50 ` [RFC PATCH net-next v7 14/14] selftests: add ncdevmem, netcat for devmem TCP Mina Almasry
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