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Wed, 26 Nov 2025 02:03:30 -0800 (PST) Date: Wed, 26 Nov 2025 10:03:30 +0000 From: Wei Yang To: "Christophe Leroy (CS GROUP)" Cc: Wei Yang , akpm@linux-foundation.org, david@kernel.org, lorenzo.stoakes@oracle.com, Liam.Howlett@oracle.com, vbabka@suse.cz, rppt@kernel.org, surenb@google.com, mhocko@suse.com, ziy@nvidia.com, baolin.wang@linux.alibaba.com, npache@redhat.com, ryan.roberts@arm.com, dev.jain@arm.com, baohua@kernel.org, lance.yang@linux.dev, linux-mm@kvack.org Subject: Re: [PATCH] mm: use standard page table accessors Message-ID: <20251126100330.n66n3uvt3junflao@master> Reply-To: Wei Yang References: <20251126064723.4053-1-richard.weiyang@gmail.com> <9c32675d-c48d-405f-a38f-4c90a8edac74@kernel.org> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <9c32675d-c48d-405f-a38f-4c90a8edac74@kernel.org> User-Agent: NeoMutt/20170113 (1.7.2) X-Rspamd-Server: rspam03 X-Rspamd-Queue-Id: A83BF40012 X-Stat-Signature: x3adt3cnyxi1fxy31fq3o8km8fafmxdw X-Rspam-User: X-HE-Tag: 1764151412-504348 X-HE-Meta: U2FsdGVkX1+OmwpthaByuqx5TkMHbAJx38P2JgI2SOUZ6dIKEHm0lwnw/9/nP+nfYHrO+PJFXxacw2pZ/OmyKCdDg5UlXMa0jVpC4UNnQ+uvlxdLeDhaFPtLAgPYAfIZTcLRs6/BDHQYht0vjpJnCNRhjY1IXPewpHezexNUv5aO+r6FW/WIBHqI5rvEGKAf8vzJF8zwpHOEnmJQsFoYAUfiMXA7RzePZXWOqXE3zyjtxSBc3aVbpfj9bwKYhIxUd1viDwSVI88Bo/78Y4Aw5xVwX7dceKvsbxIdqJB2ZRVPVttlnOZ5K8v6pVCsaJIB/bdSvMCGtCJ5vNmzVBF8uNTyfBWkB94oMNaXWwIGDDFYk7YMj00TkUnpcOPugWlYQJoSw0VzCoyOpzqyb+Xl3v5paG0QgZAciGvXd3iZr5gqaP9Uqps2VlnqOJDbiA8EPyYbr2hmsC56sBpHFff+QDI8/dbv+8SkdMWTyAIsKBsdFTascMRaEiMNL7PMJHZhfJ0NIU91LOHBQgjxRJReNtY9c2byYSAgc59Uo1TRIUb2xMn5rSW1cK+6qYM1j4cERLAQcm7fSdbo2tWNkHY9KYGCMVOtJmjs38uKLP+zJX+J8zgVmkUa5MapWDkLFXR6MHrAmqXGZVAY9pUowwREsXQS9CtICBXYyrri9FP6yNmlCiphsZ8TDvKXToJ/PMMpAKgUCVeKtEWAqFpG/U+JahjiyWMA8NL7nUVzQfCFk/Z4ylA/FkZiGWLemA/9UD5BdBZKLPBJjXLaxX6tHTCJsXl2Y/enwa8Ek13+exo/1VKuldfdvIlcwFS/zUUUg/EauHaaUtdMd1e3onQmu3zrwsRg84SxO1+zIF6wJM5SpMQ9wLPfSSdM8SwCstAVZYByDP13pr8po6+P1OUbe1c3rjST+Rb9g23uFgFGJmjCvSCRi0BTi4FELfJM7iLLiP/aU8XnrZSE+iOyV/4iQGs gfzsOxMx 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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: List-Subscribe: List-Unsubscribe: On Wed, Nov 26, 2025 at 09:15:24AM +0100, Christophe Leroy (CS GROUP) wrote: > > >Le 26/11/2025 à 07:47, Wei Yang a écrit : >> Use standard page table accessors i.e pxdp_get() to get the value of >> pxdp. > >Please provide more detail of why you want to do that and how you are sure it >doesn't break existing implementation. > >There was similar tentative in the past already which proved to give >suboptimal results, see discussion here: > >https://lore.kernel.org/all/f40ea8bf-0862-41a7-af19-70bfbd838568@csgroup.eu/ Interesting. The reason is P4D/PUD/PMD on PPC32 actually just has PGD/PMD. So it is not necessary to retrieve P4D and PUD. If this is the case, sounds other platform with less pagetable level would be affected too. And this looks only affect when we walk the pagetable from pgd. If we just iterating pmd/pte, we won't have this issue, right? > >Christophe -- Wei Yang Help you, Help me