Received-SPF: pass (google.com: domain of linux-kernel+bounces-211465-linux.lists.archive=gmail.com@vger.kernel.org designates 139.178.88.99 as permitted sender) client-ip=139.178.88.99;
Date: Wed, 12 Jun 2024 09:06:02 -0300
From: Jason Gunthorpe <jgg@ziepe.ca>
To: Mina Almasry <almasrymina@google.com>
Cc: Pavel Begunkov <asml.silence@gmail.com>,
	David Ahern <dsahern@kernel.org>, David Wei <dw@davidwei.uk>,
	Christoph Hellwig <hch@infradead.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,
	linux-trace-kernel@vger.kernel.org, linux-arch@vger.kernel.org,
	bpf@vger.kernel.org, linux-kselftest@vger.kernel.org,
	linux-media@vger.kernel.org, dri-devel@lists.freedesktop.org,
	"David S. Miller" <davem@davemloft.net>,
	Eric Dumazet <edumazet@google.com>,
	Jakub Kicinski <kuba@kernel.org>, Paolo Abeni <pabeni@redhat.com>,
	Donald Hunter <donald.hunter@gmail.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>, Andreas Larsson <andreas@gaisler.com>,
	Jesper Dangaard Brouer <hawk@kernel.org>,
	Ilias Apalodimas <ilias.apalodimas@linaro.org>,
	Steven Rostedt <rostedt@goodmis.org>,
	Masami Hiramatsu <mhiramat@kernel.org>,
	Mathieu Desnoyers <mathieu.desnoyers@efficios.com>,
	Arnd Bergmann <arnd@arndb.de>, Alexei Starovoitov <ast@kernel.org>,
	Daniel Borkmann <daniel@iogearbox.net>,
	Andrii Nakryiko <andrii@kernel.org>,
	Martin KaFai Lau <martin.lau@linux.dev>,
	Eduard Zingerman <eddyz87@gmail.com>, 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>,
	Steffen Klassert <steffen.klassert@secunet.com>,
	Herbert Xu <herbert@gondor.apana.org.au>,
	Willem de Bruijn <willemdebruijn.kernel@gmail.com>,
	Shuah Khan <shuah@kernel.org>,
	Sumit Semwal <sumit.semwal@linaro.org>,
	Christian =?utf-8?B?S8O2bmln?= <christian.koenig@amd.com>,
	Yunsheng Lin <linyunsheng@huawei.com>,
	Shailend Chand <shailend@google.com>,
	Harshitha Ramamurthy <hramamurthy@google.com>,
	Shakeel Butt <shakeel.butt@linux.dev>,
	Jeroen de Borst <jeroendb@google.com>,
	Praveen Kaligineedi <pkaligineedi@google.com>
Subject: Re: [PATCH net-next v10 02/14] net: page_pool: create hooks for
 custom page providers
Message-ID: <20240612120602.GQ791043@ziepe.ca>
References: <eb237e6e-3626-4435-8af5-11ed3931b0ac@gmail.com>
 <be2d140f-db0f-4d15-967c-972ea6586b5c@kernel.org>
 <20240607145247.GG791043@ziepe.ca>
 <45803740-442c-4298-b47e-2d87ae5a6012@davidwei.uk>
 <54975459-7a5a-46ff-a9ae-dc16ceffbab4@gmail.com>
 <20240610121625.GI791043@ziepe.ca>
 <59443d14-1f1d-42bb-8be3-73e6e4a0b683@kernel.org>
 <00c67cf0-2bf3-4eaf-b200-ffe00d91593b@gmail.com>
 <20240610221500.GN791043@ziepe.ca>
 <CAHS8izNRd=f=jHgrYKKfzgcU3JzkZA1NkZnbQM+hfYd8-0NyBQ@mail.gmail.com>
Precedence: bulk
MIME-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Content-Disposition: inline
In-Reply-To: <CAHS8izNRd=f=jHgrYKKfzgcU3JzkZA1NkZnbQM+hfYd8-0NyBQ@mail.gmail.com>

On Tue, Jun 11, 2024 at 11:09:15AM -0700, Mina Almasry wrote:

> Just curious: in Pavel's effort, io_uring - which is not a device - is
> trying to share memory with the page_pool, which is also not a device.
> And Pavel is being asked to wrap the memory in a dmabuf. Is dmabuf
> going to be the kernel's standard for any memory sharing between any 2
> components in the future, even when they're not devices?

dmabuf is how we are refcounting non-struct page memory, there is
nothing about it that says it has to be MMIO memory, or even that the
memory doesn't have struct pages.

All it says is that the memory is alive according to dmabuf
refcounting rules. And the importer obviously don't get to touch the
underlying folios, if any.

Jason