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Howlett" , Asahi Lina , linux-kernel@vger.kernel.org, rust-for-linux@vger.kernel.org, iommu@lists.linux.dev, linux-mm@kvack.org Subject: Re: [PATCH v4] io: add io_pgtable abstraction Message-ID: <20251219162734.46f3aa9d@fedora> In-Reply-To: <20251219151434.GI31492@ziepe.ca> References: <20251219-io-pgtable-v4-1-68aaa7a40380@google.com> <20251219140557.GH31492@ziepe.ca> <20251219161153.420d1c46@fedora> <20251219151434.GI31492@ziepe.ca> Organization: Collabora X-Mailer: Claws Mail 4.3.1 (GTK 3.24.51; x86_64-redhat-linux-gnu) MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit X-Rspamd-Server: rspam08 X-Rspamd-Queue-Id: 25239C0017 X-Stat-Signature: tjhsdbgggz8jxxrgc4dqd9mkdhqczdpq X-Rspam-User: X-HE-Tag: 1766158063-597654 X-HE-Meta: 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 iMDnskfd 3mxaGubqZY5N6AkIRrcPmhOds3lZHi/cAf/7h8e+qhTrb8alojvRzUPd975R9tTwlZUQOeLICQteShq0HzzrXhDqA9ChTppa0b38WnG39esP8BtmugwESw2t5MSrMq9pZmpRLpdGzK8urYh77fvXFeiqFM2V9v4hsWriY68hkaoXfLoBYYtwCAONCXb4bgyEsOZAEpeUr9uZjThTIwyhD+odcv7junsKEgbew30WkqWqud221yE5wg04HIpTIZq9p/N/8xgzmwx1E11d9KeE4HByCmcQV5QcZ+Nw7JnOpUMZNshzTI1XHThrkkdJVaFY9dwzQtEpJhwUiMe3jBJq/J68/Nqp+XBwp3NFEEEc8hP3GnjavwhX5iuQP3PxZLO2x2PEwkToIjfRuxUmU2o9bkMr70FVIamBzUjCSBF20strPCJE/7mpj/yx36n1OPlMU00M6S3mI8bQ2PkOHdcuLDCUQDTjMk8It+bobeznK2gWc8UXpq7DVtfsVBQ== 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 Fri, 19 Dec 2025 11:14:34 -0400 Jason Gunthorpe wrote: > On Fri, Dec 19, 2025 at 04:11:53PM +0100, Boris Brezillon wrote: > > > There's actually a confusion between TLB invalidation and L1/L2 cache > > flush/invalidation. The things we can decide to flush/invalidate around > > map/unmap ops are L1/L2 caches. The TLB invalidate, we don't have > > direct control on: it happens as part of the LOCK+UNLOCK sequence, and > > no matter what you execute (map or unmap), you have to surround it with > > a LOCK/UNLOCK to provide support for atomic updates (GPU is blocked if > > anything accesses the locked range while an update is on-going). > > That makes more sense, so these GPU drivers just flush the entire TLB > every time they change it - built into the UNLOCK operation? I don't have implementation details, so I can't really tell what happens internally. What's sure is that LOCK takes a range, so they might be optimizing the TLB flush to only evict entries covered by this range, dunno.