From: Shakeel Butt <shakeelb@google.com>
To: Jesper Dangaard Brouer <brouer@redhat.com>
Cc: Ilias Apalodimas <ilias.apalodimas@linaro.org>,
Matthew Wilcox <willy@infradead.org>,
Matteo Croce <mcroce@linux.microsoft.com>,
netdev <netdev@vger.kernel.org>, Linux MM <linux-mm@kvack.org>,
Ayush Sawal <ayush.sawal@chelsio.com>,
Vinay Kumar Yadav <vinay.yadav@chelsio.com>,
Rohit Maheshwari <rohitm@chelsio.com>,
"David S. Miller" <davem@davemloft.net>,
Jakub Kicinski <kuba@kernel.org>,
Thomas Petazzoni <thomas.petazzoni@bootlin.com>,
Marcin Wojtas <mw@semihalf.com>,
Russell King <linux@armlinux.org.uk>,
Mirko Lindner <mlindner@marvell.com>,
Stephen Hemminger <stephen@networkplumber.org>,
Tariq Toukan <tariqt@nvidia.com>,
Jesper Dangaard Brouer <hawk@kernel.org>,
Alexei Starovoitov <ast@kernel.org>,
Daniel Borkmann <daniel@iogearbox.net>,
John Fastabend <john.fastabend@gmail.com>,
Boris Pismenny <borisp@nvidia.com>, Arnd Bergmann <arnd@arndb.de>,
Andrew Morton <akpm@linux-foundation.org>,
"Peter Zijlstra (Intel)" <peterz@infradead.org>,
Vlastimil Babka <vbabka@suse.cz>, Yu Zhao <yuzhao@google.com>,
Will Deacon <will@kernel.org>,
Michel Lespinasse <walken@google.com>,
Fenghua Yu <fenghua.yu@intel.com>, Roman Gushchin <guro@fb.com>,
Hugh Dickins <hughd@google.com>, Peter Xu <peterx@redhat.com>,
Jason Gunthorpe <jgg@ziepe.ca>,
Guoqing Jiang <guoqing.jiang@cloud.ionos.com>,
Jonathan Lemon <jonathan.lemon@gmail.com>,
Alexander Lobakin <alobakin@pm.me>,
Cong Wang <cong.wang@bytedance.com>, wenxu <wenxu@ucloud.cn>,
Kevin Hao <haokexin@gmail.com>,
Aleksandr Nogikh <nogikh@google.com>,
Jakub Sitnicki <jakub@cloudflare.com>,
Marco Elver <elver@google.com>,
Willem de Bruijn <willemb@google.com>,
Miaohe Lin <linmiaohe@huawei.com>,
Yunsheng Lin <linyunsheng@huawei.com>,
Guillaume Nault <gnault@redhat.com>,
LKML <linux-kernel@vger.kernel.org>,
linux-rdma@vger.kernel.org, bpf <bpf@vger.kernel.org>,
Eric Dumazet <edumazet@google.com>,
David Ahern <dsahern@gmail.com>,
Lorenzo Bianconi <lorenzo@kernel.org>,
Saeed Mahameed <saeedm@nvidia.com>, Andrew Lunn <andrew@lunn.ch>,
Paolo Abeni <pabeni@redhat.com>
Subject: Re: [PATCH net-next v3 2/5] mm: add a signature in struct page
Date: Wed, 14 Apr 2021 13:09:47 -0700 [thread overview]
Message-ID: <CALvZod4F8kCQQcK5_3YH=7keqkgY-97g+_OLoDCN7uNJdd61xA@mail.gmail.com> (raw)
In-Reply-To: <20210414214132.74f721dd@carbon>
On Wed, Apr 14, 2021 at 12:42 PM Jesper Dangaard Brouer
<brouer@redhat.com> wrote:
>
[...]
> > >
> > > Can this page_pool be used for TCP RX zerocopy? If yes then PageType
> > > can not be used.
> >
> > Yes it can, since it's going to be used as your default allocator for
> > payloads, which might end up on an SKB.
>
> I'm not sure we want or should "allow" page_pool be used for TCP RX
> zerocopy.
> For several reasons.
>
> (1) This implies mapping these pages page to userspace, which AFAIK
> means using page->mapping and page->index members (right?).
>
No, only page->_mapcount is used.
> (2) It feels wrong (security wise) to keep the DMA-mapping (for the
> device) and also map this page into userspace.
>
I think this is already the case i.e pages still DMA-mapped and also
mapped into userspace.
> (3) The page_pool is optimized for refcnt==1 case, and AFAIK TCP-RX
> zerocopy will bump the refcnt, which means the page_pool will not
> recycle the page when it see the elevated refcnt (it will instead
> release its DMA-mapping).
Yes this is right but the userspace might have already consumed and
unmapped the page before the driver considers to recycle the page.
>
> (4) I remember vaguely that this code path for (TCP RX zerocopy) uses
> page->private for tricks. And our patch [3/5] use page->private for
> storing xdp_mem_info.
>
> IMHO when the SKB travel into this TCP RX zerocopy code path, we should
> call page_pool_release_page() to release its DMA-mapping.
>
I will let TCP RX zerocopy experts respond to this but from my high
level code inspection, I didn't see page->private usage.
next prev parent reply other threads:[~2021-04-14 20:10 UTC|newest]
Thread overview: 41+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-04-09 22:37 [PATCH net-next v3 0/5] page_pool: recycle buffers Matteo Croce
2021-04-09 22:37 ` [PATCH net-next v3 1/5] xdp: reduce size of struct xdp_mem_info Matteo Croce
2021-04-09 22:37 ` [PATCH net-next v3 2/5] mm: add a signature in struct page Matteo Croce
2021-04-10 15:48 ` Matthew Wilcox
2021-04-10 16:16 ` Ilias Apalodimas
2021-04-10 17:42 ` Shakeel Butt
2021-04-10 18:27 ` Ilias Apalodimas
2021-04-10 19:39 ` Matthew Wilcox
2021-04-11 10:05 ` Jesper Dangaard Brouer
2021-04-14 19:41 ` Jesper Dangaard Brouer
2021-04-14 20:09 ` Shakeel Butt [this message]
2021-04-14 20:51 ` Eric Dumazet
2021-04-19 5:12 ` Ilias Apalodimas
2021-04-19 14:57 ` Shakeel Butt
2021-04-19 15:43 ` Ilias Apalodimas
2021-04-19 16:21 ` Shakeel Butt
2021-04-19 18:41 ` Ilias Apalodimas
2021-04-19 11:22 ` Jesper Dangaard Brouer
2021-04-19 13:01 ` Matthew Wilcox
2021-04-20 8:10 ` Ilias Apalodimas
2021-04-09 22:37 ` [PATCH net-next v3 3/5] page_pool: Allow drivers to hint on SKB recycling Matteo Croce
2021-04-10 0:11 ` Ilias Apalodimas
2021-04-10 0:39 ` Matteo Croce
2021-04-09 22:38 ` [PATCH net-next v3 4/5] mvpp2: recycle buffers Matteo Croce
2021-04-09 22:38 ` [PATCH net-next v3 5/5] mvneta: " Matteo Croce
2021-04-29 8:27 ` [PATCH net-next v3 0/5] page_pool: " Yunsheng Lin
2021-04-29 18:51 ` Ilias Apalodimas
2021-04-30 3:01 ` Yunsheng Lin
2021-04-30 16:24 ` Ilias Apalodimas
2021-04-30 17:32 ` Ilias Apalodimas
2021-05-03 7:29 ` Jesper Dangaard Brouer
2021-05-06 12:34 ` Yunsheng Lin
2021-05-06 12:58 ` Ilias Apalodimas
2021-05-07 3:23 ` Yunsheng Lin
2021-05-07 7:06 ` Ilias Apalodimas
2021-05-07 8:28 ` Yunsheng Lin
2021-05-07 10:19 ` Jesper Dangaard Brouer
2021-05-07 11:31 ` Christoph Hellwig
2021-05-09 5:11 ` Shay Agroskin
2021-05-11 8:41 ` Ilias Apalodimas
2021-05-10 2:20 ` Yunsheng Lin
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