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Thu, 19 Sep 2024 19:15:11 +0800 (CST) Received: from [10.67.120.129] (10.67.120.129) by dggpemf200006.china.huawei.com (7.185.36.61) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.2.1544.11; Thu, 19 Sep 2024 19:15:11 +0800 Message-ID: Date: Thu, 19 Sep 2024 19:15:11 +0800 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird To: Jesper Dangaard Brouer , Ilias Apalodimas References: <20240918111826.863596-1-linyunsheng@huawei.com> <20240918111826.863596-3-linyunsheng@huawei.com> <894a3c2c-22f9-45b9-a82b-de7320066b42@kernel.org> Content-Language: en-US From: Yunsheng Lin In-Reply-To: <894a3c2c-22f9-45b9-a82b-de7320066b42@kernel.org> Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: 8bit X-Originating-IP: [10.67.120.129] X-ClientProxiedBy: dggems701-chm.china.huawei.com (10.3.19.178) To dggpemf200006.china.huawei.com (7.185.36.61) X-Mailman-Original-Authentication-Results: smtp3.osuosl.org; dmarc=pass (p=quarantine dis=none) header.from=huawei.com Subject: Re: [Intel-wired-lan] [PATCH net 2/2] page_pool: fix IOMMU crash when driver has already unbound X-BeenThere: intel-wired-lan@osuosl.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Intel Wired Ethernet Linux Kernel Driver Development List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: imx@lists.linux.dev, Alexei Starovoitov , Alexander Duyck , linux-mm@kvack.org, Eric Dumazet , Tony Nguyen , Shenwei Wang , Ryder Lee , Leon Romanovsky , linux-rdma@vger.kernel.org, Przemek Kitszel , John Fastabend , IOMMU , liuyonglong@huawei.com, Clark Wang , zhangkun09@huawei.com, fanghaiqing@huawei.com, pabeni@redhat.com, Lorenzo Bianconi , Kalle Valo , Sean Wang , Wei Fang , kuba@kernel.org, Matthias Brugger , intel-wired-lan@lists.osuosl.org, bpf@vger.kernel.org, linux-arm-kernel@lists.infradead.org, AngeloGioacchino Del Regno , Daniel Borkmann , Robin Murphy , linux-wireless@vger.kernel.org, linux-kernel@vger.kernel.org, Tariq Toukan , Alexander Lobakin , netdev@vger.kernel.org, linux-mediatek@lists.infradead.org, Andrew Morton , Shayne Chen , Saeed Mahameed , davem@davemloft.net, Felix Fietkau Errors-To: intel-wired-lan-bounces@osuosl.org Sender: "Intel-wired-lan" On 2024/9/19 17:42, Jesper Dangaard Brouer wrote: > > On 18/09/2024 19.06, Ilias Apalodimas wrote: >>> In order not to do the dma unmmapping after driver has already >>> unbound and stall the unloading of the networking driver, add >>> the pool->items array to record all the pages including the ones >>> which are handed over to network stack, so the page_pool can >>> do the dma unmmapping for those pages when page_pool_destroy() >>> is called. >> >> So, I was thinking of a very similar idea. But what do you mean by >> "all"? The pages that are still in caches (slow or fast) of the pool >> will be unmapped during page_pool_destroy(). > > I really dislike this idea of having to keep track of all outstanding pages. > > I liked Jakub's idea of keeping the netdev around for longer. > > This is all related to destroying the struct device that have points to > the DMA engine, right? Yes, the problem seems to be that when device_del() is called, there is no guarantee hw behind the 'struct device ' will be usable even if we call get_device() on it. > > Why don't we add an API that allow netdev to "give" struct device to > page_pool.  And then the page_poll will take over when we can safely > free the stuct device? By 'allow netdev to "give" struct device to page_pool', does it mean page_pool become the driver for the device? If yes, it seems that is similar to jakub's idea, as both seems to stall the calling of device_del() by not returning when the driver unloading. If no, it seems that the problem is still existed when the driver for the device has unbound after device_del() is called. > > --Jesper