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Miller" , "Eric Dumazet" , Paolo Abeni , Subject: Re: [PATCH net-next v1] page_pool: check for dma_sync_size earlier Message-ID: <20241011172605.0000142f@gmail.com> In-Reply-To: <21036339-3eeb-4606-9a84-d36bddba2b31@huawei.com> References: <20241010114019.1734573-1-0x1207@gmail.com> <601d59f4-d554-4431-81ca-32bb02fb541f@huawei.com> <20241011101455.00006b35@gmail.com> <20241011143158.00002eca@gmail.com> <21036339-3eeb-4606-9a84-d36bddba2b31@huawei.com> X-Mailer: Claws Mail 4.3.0 (GTK 3.24.42; x86_64-w64-mingw32) Precedence: bulk X-Mailing-List: netdev@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Hi Jakub, On Fri, 11 Oct 2024 16:55:34 +0800, Yunsheng Lin wrote: > On 2024/10/11 14:31, Furong Xu wrote: > > Hi Ilias, > > > > On Fri, 11 Oct 2024 08:06:04 +0300, Ilias Apalodimas wrote: > > > >> Hi Furong, > >> > >> On Fri, 11 Oct 2024 at 05:15, Furong Xu <0x1207@gmail.com> wrote: > >>> > >>> On Thu, 10 Oct 2024 19:53:39 +0800, Yunsheng Lin wrote: > >>> > >>>> Is there any reason that those drivers not to unset the PP_FLAG_DMA_SYNC_DEV > >>>> when calling page_pool_create()? > >>>> Does it only need dma sync for some cases and not need dma sync for other > >>>> cases? if so, why not do the dma sync in the driver instead? > >>> > >>> The answer is in this commit: > >>> https://git.kernel.org/netdev/net/c/5546da79e6cc > >> > >> I am not sure I am following. Where does the stmmac driver call a sync > >> with len 0? > > For now, only drivers/net/ethernet/freescale/fec_main.c does. > > And stmmac driver does not yet, but I will send another patch to make it call sync with > > len 0. This is a proper fix as Jakub Kicinski suggested. > > In order to support the above use case, it seems there might be two > options here: > 1. Driver calls page_pool_create() without PP_FLAG_DMA_SYNC_DEV and > handle the dma sync itself. > 2. Page_pool may provides a non-dma-sync version of page_pool_put_page() > API even when Driver calls page_pool_create() with PP_FLAG_DMA_SYNC_DEV. > > Maybe option 2 is better one in the longer term as it may provide some > flexibility for the user and enable removing of the DMA_SYNC_DEV in the > future? What is your opinion about this? Thanks.