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Date:   Tue, 14 Nov 2023 17:25:34 -0500
From:   Jakub Kicinski <kuba@kernel.org>
To:     Yunsheng Lin <linyunsheng@huawei.com>
Cc:     Mina Almasry <almasrymina@google.com>, <davem@davemloft.net>,
        <pabeni@redhat.com>, <netdev@vger.kernel.org>,
        <linux-kernel@vger.kernel.org>,
        Willem de Bruijn <willemb@google.com>,
        Kaiyuan Zhang <kaiyuanz@google.com>,
        Jesper Dangaard Brouer <hawk@kernel.org>,
        Ilias Apalodimas <ilias.apalodimas@linaro.org>,
        Eric Dumazet <edumazet@google.com>,
        Christian =?UTF-8?B?S8O2bmln?= <christian.koenig@amd.com>,
        Jason Gunthorpe <jgg@nvidia.com>,
        Matthew Wilcox <willy@infradead.org>,
        Linux-MM <linux-mm@kvack.org>
Subject: Re: [PATCH RFC 3/8] memory-provider: dmabuf devmem memory provider
Message-ID: <20231114172534.124f544c@kernel.org>
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On Tue, 14 Nov 2023 16:23:29 +0800 Yunsheng Lin wrote:
> I would expect net stack, page pool, driver still see the 'struct page',
> only memory provider see the specific struct for itself, for the above,
> devmem memory provider sees the 'struct page_pool_iov'.

You can't lie to the driver that an _iov is a page either.
The driver must explicitly "opt-in" to using the _iov variant,
by calling the _iov set of APIs.

Only drivers which can support header-data split can reasonably
use the _iov API, for data pages.