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[156.34.48.30]) by smtp.gmail.com with ESMTPSA id d21sm387410qtp.97.2020.10.05.11.37.05 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 05 Oct 2020 11:37:05 -0700 (PDT) Received: from jgg by mlx with local (Exim 4.94) (envelope-from ) id 1kPVM8-0008jm-C7; Mon, 05 Oct 2020 15:37:04 -0300 Date: Mon, 5 Oct 2020 15:37:04 -0300 From: Jason Gunthorpe To: Daniel Vetter Cc: DRI Development , LKML , Daniel Vetter , Andrew Morton , John Hubbard , =?utf-8?B?SsOpcsO0bWU=?= Glisse , Jan Kara , Dan Williams , Linux MM , Linux ARM , Pawel Osciak , Marek Szyprowski , Kyungmin Park , Tomasz Figa , 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: <20201005183704.GC5177@ziepe.ca> References: <20201002175303.390363-1-daniel.vetter@ffwll.ch> <20201002175303.390363-2-daniel.vetter@ffwll.ch> <20201002180603.GL9916@ziepe.ca> <20201002233118.GM9916@ziepe.ca> <20201004125059.GP9916@ziepe.ca> <20201005172854.GA5177@ziepe.ca> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Precedence: bulk List-ID: X-Mailing-List: linux-media@vger.kernel.org On Mon, Oct 05, 2020 at 08:16:33PM +0200, Daniel Vetter wrote: > > kvm is some similar hack added for P2P DMA, see commit > > add6a0cd1c5ba51b201e1361b05a5df817083618. It might be protected by notifiers.. > > Yeah my thinking is that kvm (and I think also vfio, also seems to > have mmu notifier nearby) are ok because of the mmu notiifer. Assuming > that one works correctly. vfio doesn't have a notifier, Alex was looking to add a vfio private scheme in the vma->private_data: https://lore.kernel.org/kvm/159017449210.18853.15037950701494323009.stgit@gimli.home/ Guess it never happened. > > So, the answer really is that s390 and media need fixing, and this API > > should go away (or become kvm specific) > > I'm still not clear how you want fo fix this, since your vma->dma_buf > idea is kinda a decade long plan and so just not going to happen: Well, it doesn't mean we have to change every part of dma_buf to participate in this. Just the bits media cares about. Or maybe it is some higher level varient on top of dma_buf. Or don't use dma_buf for this, add a new object that just provides refcounts and P2P DMA connection for IO pfn ranges.. Jason