From: Mina Almasry <almasrymina@google.com>
To: Christoph Hellwig <hch@infradead.org>
Cc: netdev@vger.kernel.org, linux-kernel@vger.kernel.org,
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Subject: Re: [RFC PATCH net-next v8 02/14] net: page_pool: create hooks for custom page providers
Date: Fri, 3 May 2024 13:10:44 -0700 [thread overview]
Message-ID: <CAHS8izM0=xc2UhUxhnF_BixuFs5VaDV9W1jbso1K+Rg=35NzeA@mail.gmail.com> (raw)
In-Reply-To: <ZjH1QaSSQ98mw158@infradead.org>
Sorry for the late reply.
On Wed, May 1, 2024 at 12:55 AM Christoph Hellwig <hch@infradead.org> wrote:
>
> Still NAK to creating aⅺbitrary hooks here.
Is the concern still that folks may be able to hook proprietary stuff
into this like you mentioned before[1]?
I don't see how that can be done as currently written. The page_pool
grabs the memory_provider_ops from the netdev_rx_queue struct managed
by core net stack and not really overridable by external modules. When
the netdev creates the page_pool, it gets the core-managed
netdev_rx_queue via something like __netif_get_rx_queue() and passes
that to page_pool_create().
We could make the memory_provider_ops even more opaque by only
allowing the device to only pass in the netdev + queue num to the
page_pool_create, and have the page_pool_create query the
netdev_rx_queue struct, to make sure we're getting the one managed by
core.
Long story short is that as currently written I think it's pretty much
impossible for someone to plug in a proprietary out-of-tree memory
provider using these hooks, and if desired I can change the code
slightly to make it even more difficult (but maybe that's pointless, I
don't think it's possible even in the current iteration). The only way
to get a memory_provider_ops in is to seek to merge it as part of the
kernel with community approval. Is there something I'm missing here?
> This should be a page or
> dmabuf pool and not an indirect call abstraction allowing random
> crap to hook into it.
>
What is the suggested fix here? I do something like:
cp net/core/page_pool.c net/core/dmabuf_pool.c
and then modify it such that the net stack maintains 2 page_pools?
There are a lot of cons to that:
1. Code duplication/maintenance (page_pool.c + dmabuf_pool.c will look
very similar).
2. The hooks enable more use cases than dmabuf_pool + standard pages.
In addition to those, I'm thinking of (but not working on):
a. Limited memory pools. I.e. a page_pool limited to a certain amount
of memory (for overcommited VMs).
b. dmabuf pools with GPU virtual addresses. Currently we seek to
support dmabuf memory where the virtual address is an offset into the
dmabuf for CPU access. For GPU memory accessible to the GPU we need
dmabuf memory where the virtual address is the GPU virtual address.
3. Support for multiple page_pools is actually more proprietary
friendly IMO. Currently the page_pool is internal to core. If we start
adding additional pools we need to have some uniform behavior between
all the pools so core can operate on memory that originated from any
one of them. In that case it becomes actually easier for someone to
develop an out of tree pool and use it from their out-of-tree driver
and as long as their out of tree page_pool behaves similarly enough to
the decided uniform behavior, it may be able to fool core into
thinking it's an in-tree pool...
[1] https://lore.kernel.org/linux-kernel/ZfegzB341oNc_Ocz@infradead.org/
--
Thanks,
Mina
next prev parent reply other threads:[~2024-05-03 20:11 UTC|newest]
Thread overview: 52+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-04-03 0:20 [RFC PATCH net-next v8 00/14] Device Memory TCP Mina Almasry
2024-04-03 0:20 ` [RFC PATCH net-next v8 01/14] queue_api: define queue api Mina Almasry
2024-04-03 0:20 ` [RFC PATCH net-next v8 02/14] net: page_pool: create hooks for custom page providers Mina Almasry
[not found] ` <ZjH1QaSSQ98mw158@infradead.org>
2024-05-03 20:10 ` Mina Almasry [this message]
[not found] ` <ZjjHUh1eINPg1wkn@infradead.org>
2024-05-07 16:05 ` Pavel Begunkov
2024-05-07 16:18 ` Jason Gunthorpe
[not found] ` <ZjpVfPqGNfE5N4bl@infradead.org>
2024-05-07 16:42 ` Mina Almasry
2024-05-07 16:48 ` Jason Gunthorpe
2024-05-07 17:19 ` Daniel Vetter
2024-05-07 17:25 ` Pavel Begunkov
2024-05-07 17:56 ` Jason Gunthorpe
2024-05-07 19:35 ` Pavel Begunkov
2024-05-07 23:32 ` Jason Gunthorpe
2024-05-08 7:16 ` Daniel Vetter
2024-05-08 11:35 ` Pavel Begunkov
2024-05-08 15:34 ` Daniel Vetter
[not found] ` <ZjufddNVJs5Csaix@infradead.org>
2024-05-08 17:02 ` Pavel Begunkov
2024-05-08 11:30 ` Pavel Begunkov
2024-05-08 14:25 ` Jason Gunthorpe
2024-05-08 15:44 ` Pavel Begunkov
2024-05-08 15:58 ` Jason Gunthorpe
2024-05-08 16:13 ` Pavel Begunkov
2024-05-07 17:17 ` Pavel Begunkov
2024-05-07 16:55 ` Pavel Begunkov
2024-05-07 17:15 ` Mina Almasry
2024-05-07 17:34 ` Pavel Begunkov
2024-04-03 0:20 ` [RFC PATCH net-next v8 03/14] net: netdev netlink api to bind dma-buf to a net device Mina Almasry
2024-04-03 0:20 ` [RFC PATCH net-next v8 04/14] netdev: support binding dma-buf to netdevice Mina Almasry
2024-04-24 17:35 ` David Wei
2024-04-24 22:11 ` Mina Almasry
2024-04-03 0:20 ` [RFC PATCH net-next v8 05/14] netdev: netdevice devmem allocator Mina Almasry
2024-04-03 0:20 ` [RFC PATCH net-next v8 06/14] page_pool: convert to use netmem Mina Almasry
2024-04-03 17:27 ` Simon Horman
2024-04-03 0:20 ` [RFC PATCH net-next v8 07/14] page_pool: devmem support Mina Almasry
2024-04-27 0:17 ` David Wei
2024-04-27 2:11 ` Mina Almasry
2024-04-30 13:31 ` Pavel Begunkov
2024-04-30 13:45 ` Jens Axboe
2024-04-30 18:29 ` Mina Almasry
2024-04-30 18:55 ` Jens Axboe
2024-04-30 19:19 ` Mina Almasry
2024-05-01 13:58 ` Jesper Dangaard Brouer
[not found] ` <ZjH1hO8qJgOqNKub@infradead.org>
2024-05-06 0:29 ` David Wei
2024-04-03 0:20 ` [RFC PATCH net-next v8 08/14] memory-provider: dmabuf devmem memory provider Mina Almasry
2024-04-03 0:20 ` [RFC PATCH net-next v8 09/14] net: support non paged skb frags Mina Almasry
2024-04-03 0:20 ` [RFC PATCH net-next v8 10/14] net: add support for skbs with unreadable frags Mina Almasry
2024-04-03 0:20 ` [RFC PATCH net-next v8 11/14] tcp: RX path for devmem TCP Mina Almasry
2024-04-03 0:20 ` [RFC PATCH net-next v8 12/14] net: add SO_DEVMEM_DONTNEED setsockopt to release RX frags Mina Almasry
2024-04-03 0:20 ` [RFC PATCH net-next v8 13/14] net: add devmem TCP documentation Mina Almasry
2024-05-03 13:14 ` Bagas Sanjaya
2024-04-03 0:20 ` [RFC PATCH net-next v8 14/14] selftests: add ncdevmem, netcat for devmem TCP Mina Almasry
2024-04-08 15:57 ` Cong Wang
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