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b=tMIiZugOhjzqgyUpW7HkIMb94kB3G/IoEOWJvEfIibHaCL2W6lxj/6dAy50ww3Upd 5BuV7yd7+xf0LnJlLA6shnOsl4ybtmmnw4qRRAcxcVdTlQQO8CjzRoHuaAPl0cnLci KyO838TcaL8c8mfnqC3Fcz2LQ0BjvUfx2U9ux0XAeez0raNOeRSjsGu9186hqHSozD ekcF76hWo/vt3sl8iQ7tBHFkSTET2nmVrmZCljeeCkxJkkq5cSQY3mp+XWQ6e0oYMf Qo62AxytxEW4fp+yzCDxcmUUB+Wme/iNSXIqef4vFQ/XRD6jqsRg+/Yl4tOtEC8q6k c8Ol4+tfmgDUA== Message-ID: <0e8c7a7a-0e2a-42ec-adbc-b29f6a514517@kernel.org> Date: Thu, 19 Sep 2024 23:04:43 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH net 2/2] page_pool: fix IOMMU crash when driver has already unbound To: Yunsheng Lin , Ilias Apalodimas Cc: davem@davemloft.net, kuba@kernel.org, pabeni@redhat.com, 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 , 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 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: Jesper Dangaard Brouer In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit X-Rspamd-Server: rspam06 X-Rspamd-Queue-Id: EF51B14001D X-Stat-Signature: 758tced9uyw3n1mau8w6mgr6mofbdbnb X-Rspam-User: X-HE-Tag: 1726779894-945377 X-HE-Meta: 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 TbAj10v8 uGDguzjcbQQ3vrcReWfUuUeulhiU2jJAxAVVZhbvCLjb2vGetRtLYjBzs/WuhyUAk3Pz6NMGz/lp6xGrGfBrP9M6GEDl0vTjXotaGJUvyjUdfHJnCSwGeRqc3Xxh3iR+wyVanOMbVdunccyUYQGUmgrrT9vHuqRA33OPeYJgZWP8tw9CU3JKkbEE0LdUcSf0MCvSuv2g1TMZy8GSZK9q+CvHyGpQGpsWlqIalWzjxwOIdQcZBUnyTvfxB5tZfj8XArnwU+wbmszM4Jqa41l+2u2wTe3e11CZxU704589tf+nvGCcFwNWvCQ2olIyu6dgHXLCxgpALiwzW5407qCq6nzOL+d38IzAAp1babAuD1rZbkPFfgxnUUJUqa2/wvjEd+Zx5LHyXAPgXCKLDACuib68oEg== 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 19/09/2024 13.15, Yunsheng Lin wrote: > 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. Yes, this is what I mean. (That is why I mentioned Jakub's idea). > If no, it seems that the problem is still existed when the driver for > the device has unbound after device_del() is called.