Re: [RFC PATCH net-next v5 08/14] memory-provider: dmabuf devmem memory provider

From: Pavel Begunkov <asml.silence@gmail.com>
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>,
	Stanislav Fomichev <sdf@google.com>, Hao Luo <haoluo@google.com>,
	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,
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	dri-devel@lists.freedesktop.org
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>,
	"Christian König" <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>
Subject: Re: [RFC PATCH net-next v5 08/14] memory-provider: dmabuf devmem memory provider
Date: Tue, 13 Feb 2024 13:19:43 +0000	[thread overview]
Message-ID: <dd4a6633-36d0-4654-a5e1-2824de29c130@gmail.com> (raw)
In-Reply-To: <20231218024024.3516870-9-almasrymina@google.com>

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