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[156.34.48.30]) by smtp.gmail.com with ESMTPSA id b9sm1325969qka.86.2020.10.07.06.42.34 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 07 Oct 2020 06:42:34 -0700 (PDT) Received: from jgg by mlx with local (Exim 4.94) (envelope-from ) id 1kQ9iE-000uYh-A3; Wed, 07 Oct 2020 10:42:34 -0300 Date: Wed, 7 Oct 2020 10:42:34 -0300 From: Jason Gunthorpe To: Tomasz Figa Cc: Daniel Vetter , Marek Szyprowski , DRI Development , LKML , Daniel Vetter , Andrew Morton , John Hubbard , =?utf-8?B?SsOpcsO0bWU=?= Glisse , Jan Kara , Dan Williams , Linux MM , Linux ARM , Pawel Osciak , Kyungmin Park , Inki Dae , Joonyoung Shim , Seung-Woo Kim , linux-samsung-soc , "open list:DMA BUFFER SHARING FRAMEWORK" , Oded Gabbay Subject: Re: [PATCH 2/2] mm/frame-vec: use FOLL_LONGTERM Message-ID: <20201007134234.GR5177@ziepe.ca> References: <725819e9-4f07-3f04-08f8-b6180406b339@samsung.com> <20201007124409.GN5177@ziepe.ca> <20201007130610.GP5177@ziepe.ca> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: 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: On Wed, Oct 07, 2020 at 03:34:01PM +0200, Tomasz Figa wrote: > I think the userptr zero-copy hack should be able to go away indeed, > given that we now have CMA that allows having carveouts backed by > struct pages and having the memory represented as DMA-buf normally. This also needs to figure out how to get references to CMA pages out of a VMA. IIRC Daniel said these are not pinnable? > How about the regular userptr use case, though? Just call pin_user_pages(), that is the easy case. > Is your intention to drop get_vaddr_frames() or we could still keep > using it and if vec->is_pfns is true: get_vaddr_frames() is dangerous, I would like it to go away. > a) if CONFIG_VIDEO_LEGACY_PFN_USERPTR is set, taint the kernel > b) otherwise just undo and fail? For the CONFIG_VIDEO_LEGACY_PFN_USERPTR case all the follow_pfn related code in get_vaddr_frames() shold move back into media and be hidden under this config. Jason