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[156.34.48.30]) by smtp.gmail.com with ESMTPSA id r58sm1532749qte.94.2020.10.21.09.37.02 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 21 Oct 2020 09:37:02 -0700 (PDT) Received: from jgg by mlx with local (Exim 4.94) (envelope-from ) id 1kVH6k-003YkE-3P; Wed, 21 Oct 2020 13:37:02 -0300 Date: Wed, 21 Oct 2020 13:37:02 -0300 From: Jason Gunthorpe To: Daniel Vetter Cc: DRI Development , LKML , KVM list , Linux MM , Linux ARM , linux-samsung-soc , "open list:DMA BUFFER SHARING FRAMEWORK" , linux-s390 , Daniel Vetter , Kees Cook , Dan Williams , Andrew Morton , John Hubbard , =?utf-8?B?SsOpcsO0bWU=?= Glisse , Jan Kara , Bjorn Helgaas , Linux PCI , Daniel Vetter Subject: Re: [PATCH v3 12/16] PCI: Obey iomem restrictions for procfs mmap Message-ID: <20201021163702.GM36674@ziepe.ca> References: <20201021085655.1192025-1-daniel.vetter@ffwll.ch> <20201021085655.1192025-13-daniel.vetter@ffwll.ch> <20201021125030.GK36674@ziepe.ca> <20201021151352.GL36674@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 21, 2020 at 05:54:54PM +0200, Daniel Vetter wrote: > The trouble is that io_remap_pfn adjust vma->pgoff, so we'd need to > split that. So ideally ->mmap would never set up any ptes. /dev/mem makes pgoff == pfn so it doesn't get changed by remap. pgoff doesn't get touched for MAP_SHARED either, so there are other users that could work like this - eg anyone mmaping IO memory is probably OK. > I guess one option would be if remap_pfn_range would steal the > vma->vm_ops pointer for itself, then it could set up the correct > ->install_ptes hook. But there's tons of callers for that, so not sure > that's a bright idea. The caller has to check that the mapping is still live, and I think hold a lock across the remap? Auto-defering it doesn't seem feasible. Jason