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[2003:cb:c707:3900:757e:83f8:a99d:41ae]) by smtp.gmail.com with ESMTPSA id q17-20020adfea11000000b0030639a86f9dsm3578463wrm.51.2023.05.17.11.23.34 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Wed, 17 May 2023 11:23:34 -0700 (PDT) Message-ID: Date: Wed, 17 May 2023 20:23:33 +0200 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:102.0) Gecko/20100101 Thunderbird/102.11.0 Subject: Re: [PATCH] tee: add FOLL_LONGTERM for CMA case when alloc shm To: Sumit Garg , Christoph Hellwig , Xiaoming Ding Cc: Jens Wiklander , Matthias Brugger , AngeloGioacchino Del Regno , op-tee@lists.trustedfirmware.org, linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-mediatek@lists.infradead.org, fei.xu@mediatek.com, srv_heupstream@mediatek.com, linux-mm@kvack.org References: <20230517031856.19660-1-xiaoming.ding@mediatek.com> From: David Hildenbrand Organization: Red Hat In-Reply-To: X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Language: en-US Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-Rspamd-Queue-Id: 2396A40011 X-Rspam-User: X-Rspamd-Server: rspam06 X-Stat-Signature: jhy1pohizef1cjyt14oq6zqm3jioxk43 X-HE-Tag: 1684347820-388514 X-HE-Meta: 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 +8XsmK4i 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 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 17.05.23 12:19, Sumit Garg wrote: > On Wed, 17 May 2023 at 15:06, Christoph Hellwig wrote: >> >> On Wed, May 17, 2023 at 02:56:13PM +0530, Sumit Garg wrote: >>> Do you mean a pinned user-space page can be paged out automatically? >> >> No, pinned pages can't be paged out. >> >> But a short term pin implies it will be release after a short delay, >> and it is feasible for wait for the pin to go away. > > Okay, I see. I would be interested to know the ranges for that short > delay. I guess it may depend on how much memory pressure there is... > In general: if user space controls it -> possibly forever -> long-term. Even if in most cases it's a short delay: there is no trusting on user space. For example, iouring fixed buffers keep pages pinned until user space decides to unregistered the buffers -> long-term. Short-term is, for example, something like O_DIRECT where we pin -> DMA -> unpin in essentially one operation. -- Thanks, David / dhildenb