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Message-ID: <da42cea9-c169-599e-f087-d38c419e3dab@huawei.com>
Date: Tue, 5 Mar 2024 20:55:09 +0800
From: Yunsheng Lin <linyunsheng@...wei.com>
To: Mina Almasry <almasrymina@...gle.com>, <netdev@...r.kernel.org>,
<linux-kernel@...r.kernel.org>, <linux-doc@...r.kernel.org>,
<linux-alpha@...r.kernel.org>, <linux-mips@...r.kernel.org>,
<linux-parisc@...r.kernel.org>, <sparclinux@...r.kernel.org>,
<linux-trace-kernel@...r.kernel.org>, <linux-arch@...r.kernel.org>,
<bpf@...r.kernel.org>, <linux-kselftest@...r.kernel.org>,
<linux-media@...r.kernel.org>, <dri-devel@...ts.freedesktop.org>
CC: "David S. Miller" <davem@...emloft.net>, Eric Dumazet
<edumazet@...gle.com>, Jakub Kicinski <kuba@...nel.org>, Paolo Abeni
<pabeni@...hat.com>, Jonathan Corbet <corbet@....net>, Richard Henderson
<richard.henderson@...aro.org>, Ivan Kokshaysky <ink@...assic.park.msu.ru>,
Matt Turner <mattst88@...il.com>, Thomas Bogendoerfer
<tsbogend@...ha.franken.de>, "James E.J. Bottomley"
<James.Bottomley@...senPartnership.com>, Helge Deller <deller@....de>,
Andreas Larsson <andreas@...sler.com>, Jesper Dangaard Brouer
<hawk@...nel.org>, Ilias Apalodimas <ilias.apalodimas@...aro.org>, Steven
Rostedt <rostedt@...dmis.org>, Masami Hiramatsu <mhiramat@...nel.org>,
Mathieu Desnoyers <mathieu.desnoyers@...icios.com>, Arnd Bergmann
<arnd@...db.de>, Alexei Starovoitov <ast@...nel.org>, Daniel Borkmann
<daniel@...earbox.net>, Andrii Nakryiko <andrii@...nel.org>, Martin KaFai Lau
<martin.lau@...ux.dev>, Eduard Zingerman <eddyz87@...il.com>, Song Liu
<song@...nel.org>, Yonghong Song <yonghong.song@...ux.dev>, John Fastabend
<john.fastabend@...il.com>, KP Singh <kpsingh@...nel.org>, Stanislav Fomichev
<sdf@...gle.com>, Hao Luo <haoluo@...gle.com>, Jiri Olsa <jolsa@...nel.org>,
David Ahern <dsahern@...nel.org>, Willem de Bruijn
<willemdebruijn.kernel@...il.com>, Shuah Khan <shuah@...nel.org>, Sumit
Semwal <sumit.semwal@...aro.org>, Christian König
<christian.koenig@....com>, Pavel Begunkov <asml.silence@...il.com>, David
Wei <dw@...idwei.uk>, Jason Gunthorpe <jgg@...pe.ca>, Shailend Chand
<shailend@...gle.com>, Harshitha Ramamurthy <hramamurthy@...gle.com>, Shakeel
Butt <shakeelb@...gle.com>, Jeroen de Borst <jeroendb@...gle.com>, Praveen
Kaligineedi <pkaligineedi@...gle.com>, Willem de Bruijn <willemb@...gle.com>,
Kaiyuan Zhang <kaiyuanz@...gle.com>
Subject: Re: [RFC PATCH net-next v6 05/15] netdev: support binding dma-buf to
netdevice
On 2024/3/5 10:01, Mina Almasry wrote:
...
>
> 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@...gle.com>
> Signed-off-by: Kaiyuan Zhang <kaiyuanz@...gle.com>
> Signed-off-by: Mina Almasry <almasrymina@...gle.com>
>
> ---
>
> RFC v6:
> - Validate rx queue index
> - Refactor new functions into devmem.c (Pavel)
It seems odd that the functions or stucts in a file called devmem.c
are named after 'dmabuf' instead of 'devmem'.
>
...
> diff --git a/include/net/netmem.h b/include/net/netmem.h
> index d8b810245c1d..72e932a1a948 100644
> --- a/include/net/netmem.h
> +++ b/include/net/netmem.h
> @@ -8,6 +8,16 @@
> #ifndef _NET_NETMEM_H
> #define _NET_NETMEM_H
>
> +#include <net/devmem.h>
> +
> +/* net_iov */
> +
> +struct net_iov {
> + struct dmabuf_genpool_chunk_owner *owner;
> +};
> +
> +/* netmem */
> +
> /**
> * typedef netmem_ref - a nonexistent type marking a reference to generic
> * network memory.
> diff --git a/net/core/Makefile b/net/core/Makefile
> index 821aec06abf1..592f955c1241 100644
> --- a/net/core/Makefile
> +++ b/net/core/Makefile
> @@ -13,7 +13,7 @@ obj-y += dev.o dev_addr_lists.o dst.o netevent.o \
> neighbour.o rtnetlink.o utils.o link_watch.o filter.o \
> sock_diag.o dev_ioctl.o tso.o sock_reuseport.o \
> fib_notifier.o xdp.o flow_offload.o gro.o \
> - netdev-genl.o netdev-genl-gen.o gso.o
> + netdev-genl.o netdev-genl-gen.o gso.o devmem.o
>
> obj-$(CONFIG_NETDEV_ADDR_LIST_TEST) += dev_addr_lists_test.o
>
> diff --git a/net/core/dev.c b/net/core/dev.c
> index fe054cbd41e9..bbea1b252529 100644
> --- a/net/core/dev.c
> +++ b/net/core/dev.c
> @@ -155,6 +155,9 @@
> #include <net/netdev_rx_queue.h>
> #include <net/page_pool/types.h>
> #include <net/page_pool/helpers.h>
> +#include <linux/genalloc.h>
> +#include <linux/dma-buf.h>
> +#include <net/devmem.h>
>
> #include "dev.h"
> #include "net-sysfs.h"
> diff --git a/net/core/devmem.c b/net/core/devmem.c
> new file mode 100644
> index 000000000000..779ad990971e
> --- /dev/null
> +++ b/net/core/devmem.c
> @@ -0,0 +1,293 @@
> +// SPDX-License-Identifier: GPL-2.0-or-later
> +/*
> + * Devmem TCP
> + *
> + * Authors: Mina Almasry <almasrymina@...gle.com>
> + * Willem de Bruijn <willemdebruijn.kernel@...il.com>
> + * Kaiyuan Zhang <kaiyuanz@...gle.com
> + */
> +
> +#include <linux/types.h>
> +#include <linux/mm.h>
> +#include <linux/netdevice.h>
> +#include <trace/events/page_pool.h>
> +#include <net/netdev_rx_queue.h>
> +#include <net/page_pool/types.h>
> +#include <net/page_pool/helpers.h>
> +#include <linux/genalloc.h>
> +#include <linux/dma-buf.h>
> +#include <net/devmem.h>
> +
> +/* Device memory support */
> +
> +#ifdef CONFIG_DMA_SHARED_BUFFER
I still think it is worth adding its own config for devmem or dma-buf
for networking, thinking about the embeded system.
> +static void netdev_dmabuf_free_chunk_owner(struct gen_pool *genpool,
> + struct gen_pool_chunk *chunk,
> + void *not_used)
It seems odd to still keep the netdev_ prefix as it is not really related
to netdev, perhaps use 'net_' or something better.
> +{
> + struct dmabuf_genpool_chunk_owner *owner = chunk->owner;
> +
> + kvfree(owner->niovs);
> + kfree(owner);
> +}
> +
> +void __netdev_dmabuf_binding_free(struct netdev_dmabuf_binding *binding)
> +{
> + size_t size, avail;
> +
> + gen_pool_for_each_chunk(binding->chunk_pool,
> + netdev_dmabuf_free_chunk_owner, NULL);
> +
> + size = gen_pool_size(binding->chunk_pool);
> + avail = gen_pool_avail(binding->chunk_pool);
> +
> + if (!WARN(size != avail, "can't destroy genpool. size=%lu, avail=%lu",
> + size, avail))
> + gen_pool_destroy(binding->chunk_pool);
> +
> + dma_buf_unmap_attachment(binding->attachment, binding->sgt,
> + DMA_BIDIRECTIONAL);
For now DMA_FROM_DEVICE seems enough as tx is not supported yet.
> + dma_buf_detach(binding->dmabuf, binding->attachment);
> + dma_buf_put(binding->dmabuf);
> + xa_destroy(&binding->bound_rxq_list);
> + kfree(binding);
> +}
> +
> +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.
> +
> +err_free_new_mem:
> + dev->netdev_ops->ndo_queue_mem_free(dev, new_mem);
> +
> + return err;
> +}
> +
> +/* Protected by rtnl_lock() */
> +static DEFINE_XARRAY_FLAGS(netdev_dmabuf_bindings, XA_FLAGS_ALLOC1);
> +
> +void netdev_unbind_dmabuf(struct netdev_dmabuf_binding *binding)
> +{
> + struct netdev_rx_queue *rxq;
> + unsigned long xa_idx;
> + unsigned int rxq_idx;
> +
> + if (!binding)
> + return;
> +
> + if (binding->list.next)
> + list_del(&binding->list);
The above does not seems to be a good pattern to delete a entry, is
there any reason having a checking before the list_del()? seems like
defensive programming?
> +
> + xa_for_each(&binding->bound_rxq_list, xa_idx, rxq) {
> + if (rxq->binding == binding) {
It seems like defensive programming here too?
> + /* 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->binding, NULL);
> +
> + rxq_idx = get_netdev_rx_queue_index(rxq);
> +
> + netdev_restart_rx_queue(binding->dev, rxq_idx);
> + }
> + }
> +
> + xa_erase(&netdev_dmabuf_bindings, binding->id);
> +
> + netdev_dmabuf_binding_put(binding);
> +}
> +
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