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[146.241.47.72]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-42f7a01fc92sm10806665e9.36.2024.10.02.00.37.55 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Wed, 02 Oct 2024 00:37:57 -0700 (PDT) Message-ID: <4316fa2d-8dd8-44f2-b211-4b2ef3200d75@redhat.com> Date: Wed, 2 Oct 2024 09:37:54 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH net v2 2/2] page_pool: fix IOMMU crash when driver has already unbound To: Yunsheng Lin , Yunsheng Lin , Ilias Apalodimas Cc: liuyonglong@huawei.com, fanghaiqing@huawei.com, zhangkun09@huawei.com, Robin Murphy , Alexander Duyck , IOMMU , Wei Fang , Shenwei Wang , Clark Wang , Eric Dumazet , Tony Nguyen , Przemek Kitszel , Alexander Lobakin , Alexei Starovoitov , Daniel Borkmann , Jesper Dangaard Brouer , John Fastabend , Saeed Mahameed , Leon Romanovsky , Tariq Toukan , Felix Fietkau , Lorenzo Bianconi , Ryder Lee , Shayne Chen , Sean Wang , Kalle Valo , Matthias Brugger , AngeloGioacchino Del Regno , Andrew Morton , imx@lists.linux.dev, netdev@vger.kernel.org, linux-kernel@vger.kernel.org, intel-wired-lan@lists.osuosl.org, bpf@vger.kernel.org, linux-rdma@vger.kernel.org, linux-wireless@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-mediatek@lists.infradead.org, linux-mm@kvack.org, davem@davemloft.net, kuba@kernel.org References: <20240925075707.3970187-1-linyunsheng@huawei.com> <20240925075707.3970187-3-linyunsheng@huawei.com> <4968c2ec-5584-4a98-9782-143605117315@redhat.com> <33f23809-abec-4d39-ab80-839dc525a2e6@gmail.com> From: Paolo Abeni In-Reply-To: <33f23809-abec-4d39-ab80-839dc525a2e6@gmail.com> X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Language: en-US Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-Stat-Signature: 6tsbmhzqhw86iy9ydtph68auxwbjsw7e X-Rspamd-Queue-Id: 21F6A20018 X-Rspam-User: X-Rspamd-Server: rspam10 X-HE-Tag: 1727854681-772513 X-HE-Meta: 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 BDvhoGzj 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 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: Hi, On 10/2/24 04:34, Yunsheng Lin wrote: > On 10/1/2024 9:32 PM, Paolo Abeni wrote: >> Is the problem only tied to VFs drivers? It's a pity all the page_pool >> users will have to pay a bill for it... > > I am afraid it is not only tied to VFs drivers, as: > attempting DMA unmaps after the driver has already unbound may leak > resources or at worst corrupt memory. > > Unloading PFs driver might cause the above problems too, I guess the > probability of crashing is low for the PF as PF can not be disable > unless it can be hot-unplug'ed, but the probability of leaking resources > behind the dma mapping might be similar. Out of sheer ignorance, why/how the refcount acquired by the page pool on the device does not prevent unloading? I fear the performance impact could be very high: AFICS, if the item array become fragmented, insertion will take linar time, with the quite large item_count/pool size. If so, it looks like a no-go. I fear we should consider blocking the device removal until all the pages are returned/unmapped ?!? (I hope that could be easier/faster) /P