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Date: Mon, 13 Nov 2023 17:10:58 -0500
From: Jakub Kicinski <kuba@kernel.org>
To: Mina Almasry <almasrymina@google.com>
Cc: netdev@vger.kernel.org, linux-kernel@vger.kernel.org,
 linux-arch@vger.kernel.org, linux-kselftest@vger.kernel.org,
 linux-media@vger.kernel.org, dri-devel@lists.freedesktop.org,
 linaro-mm-sig@lists.linaro.org, "David S. Miller" <davem@davemloft.net>,
 Eric Dumazet <edumazet@google.com>, Paolo Abeni <pabeni@redhat.com>, Jesper
 Dangaard Brouer <hawk@kernel.org>, Ilias Apalodimas
 <ilias.apalodimas@linaro.org>, Arnd Bergmann <arnd@arndb.de>, David Ahern
 <dsahern@kernel.org>, 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>, Shakeel Butt
 <shakeelb@google.com>, Jeroen de Borst <jeroendb@google.com>, Praveen
 Kaligineedi <pkaligineedi@google.com>
Subject: Re: [RFC PATCH v3 02/12] net: page_pool: create hooks for custom
 page providers
Message-ID: <20231113171058.68973860@kernel.org>
In-Reply-To: <CAHS8izPKRh7ukRytXaweKcY_76sE7F_3s1sYVgsUXYGrypK93Q@mail.gmail.com>
References: <20231106024413.2801438-1-almasrymina@google.com>
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On Sun, 12 Nov 2023 19:28:52 -0800 Mina Almasry wrote:
> My issue with this is that if the driver doesn't support dmabuf then
> the driver will accidentally use the pp backed by the dmabuf, allocate
> a page from it, then call page_address() on it or something, and
> crash.
> 
> Currently I avoid that by having the driver be responsible for picking
> up the dmabuf from the netdev_rx_queue and giving it to the page pool.
> What would be the appropriate way to check for driver support in the
> netlink API? Perhaps adding something to ndo_features_check?

We need some form of capabilities. I was expecting to add that as part
of the queue API. Either a new field in struct net_device or in ndos.
I tend to put static driver caps of this nature into ops.
See for instance .supported_ring_params in ethtool ops.