linux-kernel - Re: [RFC PATCH net-next v8 02/14] net: page_pool: create hooks for custom page providers

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [day] [month] [year] [list]

Date: Wed, 8 May 2024 21:49:39 -0700
From: Christoph Hellwig <hch@...radead.org>
To: Pavel Begunkov <asml.silence@...il.com>
Cc: Christoph Hellwig <hch@...radead.org>, Jason Gunthorpe <jgg@...pe.ca>,
	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,
	"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>,
	Steffen Klassert <steffen.klassert@...unet.com>,
	Herbert Xu <herbert@...dor.apana.org.au>,
	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>,
	Amritha Nambiar <amritha.nambiar@...el.com>,
	Maciej Fijalkowski <maciej.fijalkowski@...el.com>,
	Alexander Mikhalitsyn <alexander@...alicyn.com>,
	Kaiyuan Zhang <kaiyuanz@...gle.com>,
	Christian Brauner <brauner@...nel.org>,
	Simon Horman <horms@...nel.org>,
	David Howells <dhowells@...hat.com>,
	Florian Westphal <fw@...len.de>,
	Yunsheng Lin <linyunsheng@...wei.com>,
	Kuniyuki Iwashima <kuniyu@...zon.com>, Jens Axboe <axboe@...nel.dk>,
	Arseniy Krasnov <avkrasnov@...utedevices.com>,
	Aleksander Lobakin <aleksander.lobakin@...el.com>,
	Michael Lass <bevan@...co.net>, Jiri Pirko <jiri@...nulli.us>,
	Sebastian Andrzej Siewior <bigeasy@...utronix.de>,
	Lorenzo Bianconi <lorenzo@...nel.org>,
	Richard Gobert <richardbgobert@...il.com>,
	Sridhar Samudrala <sridhar.samudrala@...el.com>,
	Xuan Zhuo <xuanzhuo@...ux.alibaba.com>,
	Johannes Berg <johannes.berg@...el.com>,
	Abel Wu <wuyun.abel@...edance.com>,
	Breno Leitao <leitao@...ian.org>, David Wei <dw@...idwei.uk>,
	Shailend Chand <shailend@...gle.com>,
	Harshitha Ramamurthy <hramamurthy@...gle.com>,
	Shakeel Butt <shakeel.butt@...ux.dev>,
	Jeroen de Borst <jeroendb@...gle.com>,
	Praveen Kaligineedi <pkaligineedi@...gle.com>
Subject: Re: [RFC PATCH net-next v8 02/14] net: page_pool: create hooks for
 custom page providers

On Wed, May 08, 2024 at 06:02:14PM +0100, Pavel Begunkov wrote:
> Well, the example fell flat, but you don't use dmabuf when there are
> no upsides from using it. For instance, when you already have pinned
> pages, you're going to use pages, and there are no other refcounting
> concerns.

Sure.

> Unless there is an advantage of dmabufs over FOLL_LONGTERM
> that I don't know about when used with normal user pages.

The advantages of using a dma-buf over FOLL_LONGTERM are:

 a) you pre-dma map, which is a significant performance advantage for
    IOMMU-based setups
 b) you support any dma-buf exported and not just user memory.  This
    is primarily important for PCIe P2P, but there might be other
    useful exporters as well

> > wish io_uring would have just implemented them from the start instead of
> > the current fixed buffers that are not quite as useful by not
> > pre-mapping DMA and not supporting P2P.
> 
> fdget(dmabuf) would be horrible, I assume that's not the suggestion.

I'm not even sure what you mean with that.