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WOW64; rv:52.0) Gecko/20100101 Thunderbird/52.2.0 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset="utf-8" Content-Language: en-US Content-Transfer-Encoding: 7bit X-Originating-IP: [10.69.30.204] X-ClientProxiedBy: dggems703-chm.china.huawei.com (10.3.19.180) To dggpemm500005.china.huawei.com (7.185.36.74) X-CFilter-Loop: Reflected X-Rspam-User: X-Stat-Signature: 4uag3k38tprzentzpsjegg1mpy7mqbsk X-Rspamd-Server: rspam07 X-Rspamd-Queue-Id: 2D48F40005 X-HE-Tag: 1700220469-363741 X-HE-Meta: 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 44eEVqAi dfAbJqDMYnIuCz1y8JS7wlI1lmPlSk8NRpie2x0skimxCb997YyUCyLYQX+vi3YHs0L9kWjgkZ6u3bpoDPW/SqtkepV4+Ap63yMS87+pCsLhruKNwCvVCiIzhZXsaPOUGJeUSCdK7u+CXe0iek3xIZ/CyDipGKObZ3nsRq1S0uTz3CBoAvYfaxsUgZkFt302lpif8h7iRxzcV9D8UMI3ABu7kAa4UeD+LJQtx X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On 2023/11/16 23:58, David Ahern wrote: > On 11/16/23 4:12 AM, Yunsheng Lin wrote: >> On 2023/11/16 1:57, David Ahern wrote: >>> On 11/15/23 2:21 AM, Yunsheng Lin wrote: >>>> On 2023/11/14 21:16, Jason Gunthorpe wrote: >>>>> On Tue, Nov 14, 2023 at 04:21:26AM -0800, Mina Almasry wrote: >>>>> >>>>>> Actually because you put the 'strtuct page for devmem' in >>>>>> skb->bv_frag, the net stack will grab the 'struct page' for devmem >>>>>> using skb_frag_page() then call things like page_address(), kmap, >>>>>> get_page, put_page, etc, etc, etc. >>>>> >>>>> Yikes, please no. If net has its own struct page look alike it has to >>>>> stay entirely inside net. A non-mm owned struct page should not be >>>>> passed into mm calls. It is just way too hacky to be seriously >>>>> considered :( >>>> >>>> Yes, that is something this patchset is trying to do, defining its own >>>> struct page look alike for page pool to support devmem. >>>> >>> >>> Networking needs to be able to move away from struct page references. >>> The devmem and host memory for Rx use cases do not need to be page based. >> >> Yes, I am agreed the ultimate goal is to move away from struct page >> references. But I am not sure if we can do it right away as there >> still are different types of existing 'struct page' in the netstack, >> see: >> >> https://lore.kernel.org/all/8b7d25eb-1f10-3e37-8753-92b42da3fb34@huawei.com/ > > yes, that is the point of a blended approach -- pages and buffers (or > iov) -- leveraging the LSB of the address. That proposal is the right I am not sure leveraging the LSB of the address is necessary yet, as it does not seems to provide the type check protection, it seems to just provide a way to demux between pages(including page pool owned page and non-page pool owned page) and page pool owned buffer. That info is avaliable through the page->pp_magic and page->pp->mp_* too if we mirror the page pool specific union in 'struct page'. > direction to be moving for co-existence. Adding fake struct page > instances is the wrong direction. Perhaps a fake struct page with type check protection is the right direction? Intergrating devmem to page pool without a unified metadata between pages and buffers or without a proper abstract layer does not seems like the good direction either. > . >