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Date: Tue, 13 Feb 2024 13:19:43 +0000
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Subject: Re: [RFC PATCH net-next v5 08/14] memory-provider: dmabuf devmem
 memory provider
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To: Mina Almasry <almasrymina@google.com>,
 Mathieu Desnoyers <mathieu.desnoyers@efficios.com>,
 Martin KaFai Lau <martin.lau@linux.dev>, Song Liu <song@kernel.org>,
 Yonghong Song <yonghong.song@linux.dev>,
 John Fastabend <john.fastabend@gmail.com>, KP Singh <kpsingh@kernel.org>,
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 Jiri Olsa <jolsa@kernel.org>, netdev@vger.kernel.org,
 linux-kernel@vger.kernel.org, linux-doc@vger.kernel.org,
 linux-alpha@vger.kernel.org, linux-mips@vger.kernel.org,
 linux-parisc@vger.kernel.org, sparclinux@vger.kernel.org,
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 bpf@vger.kernel.org, linux-kselftest@vger.kernel.org,
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Cc: "David S. Miller" <davem@davemloft.net>,
 Eric Dumazet <edumazet@google.com>, Jakub Kicinski <kuba@kernel.org>,
 Paolo Abeni <pabeni@redhat.com>, Jonathan Corbet <corbet@lwn.net>,
 Richard Henderson <richard.henderson@linaro.org>,
 Ivan Kokshaysky <ink@jurassic.park.msu.ru>, Matt Turner
 <mattst88@gmail.com>, Thomas Bogendoerfer <tsbogend@alpha.franken.de>,
 "James E.J. Bottomley" <James.Bottomley@HansenPartnership.com>,
 Helge Deller <deller@gmx.de>, Jesper Dangaard Brouer <hawk@kernel.org>,
 Ilias Apalodimas <ilias.apalodimas@linaro.org>,
 Steven Rostedt <rostedt@goodmis.org>, Masami Hiramatsu
 <mhiramat@kernel.org>, Arnd Bergmann <arnd@arndb.de>,
 Alexei Starovoitov <ast@kernel.org>, Daniel Borkmann <daniel@iogearbox.net>,
 Andrii Nakryiko <andrii@kernel.org>, David Ahern <dsahern@kernel.org>,
 Willem de Bruijn <willemdebruijn.kernel@gmail.com>,
 Shuah Khan <shuah@kernel.org>, Sumit Semwal <sumit.semwal@linaro.org>,
 =?UTF-8?Q?Christian_K=C3=B6nig?= <christian.koenig@amd.com>,
 David Wei <dw@davidwei.uk>, Jason Gunthorpe <jgg@ziepe.ca>,
 Yunsheng Lin <linyunsheng@huawei.com>, Shailend Chand <shailend@google.com>,
 Harshitha Ramamurthy <hramamurthy@google.com>,
 Shakeel Butt <shakeelb@google.com>, Jeroen de Borst <jeroendb@google.com>,
 Praveen Kaligineedi <pkaligineedi@google.com>,
 Willem de Bruijn <willemb@google.com>, Kaiyuan Zhang <kaiyuanz@google.com>
References: <20231218024024.3516870-1-almasrymina@google.com>
 <20231218024024.3516870-9-almasrymina@google.com>
From: Pavel Begunkov <asml.silence@gmail.com>
In-Reply-To: <20231218024024.3516870-9-almasrymina@google.com>
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On 12/18/23 02:40, Mina Almasry wrote:
> Implement a memory provider that allocates dmabuf devmem in the form of
> net_iov.
> 
> The provider receives a reference to the struct netdev_dmabuf_binding
> via the pool->mp_priv pointer. The driver needs to set this pointer for
> the provider in the net_iov.
> 
> The provider obtains a reference on the netdev_dmabuf_binding which
> guarantees the binding and the underlying mapping remains alive until
> the provider is destroyed.
> 
> Usage of PP_FLAG_DMA_MAP is required for this memory provide such that
> the page_pool can provide the driver with the dma-addrs of the devmem.
> 
> Support for PP_FLAG_DMA_SYNC_DEV is omitted for simplicity & p.order !=
> 0.
> 
> 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>
> 
> ---
..
> +
> +static bool mp_dmabuf_devmem_release_page(struct page_pool *pool,
> +					  struct netmem *netmem)
> +{
> +	WARN_ON_ONCE(!netmem_is_net_iov(netmem));
> +
> +	page_pool_clear_pp_info(netmem);
> +
> +	netdev_free_dmabuf(netmem_to_net_iov(netmem));
> +
> +	/* We don't want the page pool put_page()ing our net_iovs. */
> +	return false;
> +}
> +
> +const struct memory_provider_ops dmabuf_devmem_ops = {
> +	.init			= mp_dmabuf_devmem_init,
> +	.destroy		= mp_dmabuf_devmem_destroy,
> +	.alloc_pages		= mp_dmabuf_devmem_alloc_pages,
> +	.release_page		= mp_dmabuf_devmem_release_page,
> +};
> +EXPORT_SYMBOL(dmabuf_devmem_ops);

It might make sense to move all these functions together with
new code from core/dev.c into a new file

-- 
Pavel Begunkov