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Mon, 15 Jul 2024 01:52:26 -0700 (PDT) Received: from phenom.ffwll.local ([2a02:168:57f4:0:efd0:b9e5:5ae6:c2fa]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-4279f2cc306sm113442395e9.30.2024.07.15.01.52.25 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 15 Jul 2024 01:52:26 -0700 (PDT) Date: Mon, 15 Jul 2024 10:52:23 +0200 From: Daniel Vetter To: Christian =?iso-8859-1?Q?K=F6nig?= Cc: Lei Liu , Sumit Semwal , Benjamin Gaignard , Brian Starkey , John Stultz , "T.J. Mercier" , Andrew Morton , David Hildenbrand , Matthew Wilcox , Muhammad Usama Anjum , Andrei Vagin , Ryan Roberts , Kefeng Wang , linux-media@vger.kernel.org, dri-devel@lists.freedesktop.org, linaro-mm-sig@lists.linaro.org, linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-mm@kvack.org, Daniel Vetter , "Vetter, Daniel" , opensource.kernel@vivo.com Subject: Re: [PATCH 0/2] Support direct I/O read and write for memory allocated by dmabuf Message-ID: Mail-Followup-To: Christian =?iso-8859-1?Q?K=F6nig?= , Lei Liu , Sumit Semwal , Benjamin Gaignard , Brian Starkey , John Stultz , "T.J. Mercier" , Andrew Morton , David Hildenbrand , Matthew Wilcox , Muhammad Usama Anjum , Andrei Vagin , Ryan Roberts , Kefeng Wang , linux-media@vger.kernel.org, dri-devel@lists.freedesktop.org, linaro-mm-sig@lists.linaro.org, linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-mm@kvack.org, "Vetter, Daniel" , opensource.kernel@vivo.com References: <20240710135757.25786-1-liulei.rjpt@vivo.com> <5e5ee5d3-8a57-478a-9ce7-b40cab60b67d@amd.com> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <5e5ee5d3-8a57-478a-9ce7-b40cab60b67d@amd.com> X-Operating-System: Linux phenom 6.9.7-amd64 X-Stat-Signature: tjems1e74nfstkaxwjehsabu4zyua9yc X-Rspam-User: X-Rspamd-Queue-Id: 89FEB40002 X-Rspamd-Server: rspam02 X-HE-Tag: 1721033550-299461 X-HE-Meta: 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 dsVybLLL w67zzOEN2/2YDvqyqPq6IGZtPtZkr/RAVD8H/fHeiTScJW5GgsmipgrJrGvC5QrrJh+U4EYemHgJssCskO2SKjwZA+WcR6Xs8uPvfzWsHwTw4IDD0WL+gQMFrzb6DqgDqaAkPFRtHDuIK1pyZeRecgEusBmQk5sUn5r1GWmsSlSmvuvPHsWl7PVRC+/8ocJGAXpHE4M1vH+0pYV2vEdcujy/kqYdhBs6BovjFQuT75tWg9x/zbBrU9H+/bs96rOLsk9Sn1hOl3fWYEftv09lW+cJ8hMlOp22aPP0GGOahlcZd8Rc= 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 Wed, Jul 10, 2024 at 04:14:18PM +0200, Christian König wrote: > Am 10.07.24 um 15:57 schrieb Lei Liu: > > Use vm_insert_page to establish a mapping for the memory allocated > > by dmabuf, thus supporting direct I/O read and write; and fix the > > issue of incorrect memory statistics after mapping dmabuf memory. > > Well big NAK to that! Direct I/O is intentionally disabled on DMA-bufs. > > We already discussed enforcing that in the DMA-buf framework and this patch > probably means that we should really do that. Last time I looked dma_mmap doesn't guarantee that the vma end sup with VM_SPECIAL, and that's pretty much the only reason why we can't enforce this. But we might be able to enforce this at least on some architectures, I didn't check for that ... if at least x86-64 and arm64 could have the check, that would be great. So might be worth it to re-audit this all. I think all other dma-buf exporters/allocators do only create VM_SPECIAL vmas. -Sima -- Daniel Vetter Software Engineer, Intel Corporation http://blog.ffwll.ch