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AJvYcCVsOr5CeGI3zFANSPqIMNN5VfOLihK7S8K9NOClfYJABhugqA9EAOQvJjLFybI7pBlWO92Zk32GNQ==@kvack.org X-Gm-Message-State: AOJu0YyGUAjplzdEqpfSxuTR93Kr31kydmkyGCVBBXGMCiRuMRCyyVpc rELw4vfdUtYNeWn/kZtw6WVGmOcadvyCEs2qAmhC6NWTkEePvVL38cLd5Do/JGWbJcyVzweC8YL 0xBo8Ejlmdf+lax8Iglo6e36zC0d1el5qqm2JGxsAEg== X-Gm-Gg: ASbGncv/+GNirIIEH0WVviD3NAA9aDjEInOJh96PW8seZ5vJ2D0b0EF5nejqietHRnw 0qoxWViZ5TWdDKf6CjjtxYPp6NFqinLAR7JjA1NMiOQV3Np1bWZY85poQPEGa55BwhEZesJI+PI eGGgzXJYFc0X7V9mUDmf43GoQAaME0fSNernVhXlt+C+EBJFWtEo2F/PbicScCCtQMWusxsa/xv bH5Izc= X-Google-Smtp-Source: AGHT+IFceSrS+iukkr/XkXsYJuXAC3/mzUt2kTyPUu5TFhzIuaRO7o+4f66lybawSyOyyY1O0N/R5wKHhfBQZAMqWCU= X-Received: by 2002:a05:651c:23c5:20b0:339:1b54:b367 with SMTP id 38308e7fff4ca-3513b296a39mr5927901fa.18.1757681205355; Fri, 12 Sep 2025 05:46:45 -0700 (PDT) MIME-Version: 1.0 References: <4ff89b72-03ff-4447-9d21-dd6a5fe1550f@app.fastmail.com> <497308537.21756.1757513073548.JavaMail.zimbra@nod.at> <640041197.22387.1757536385810.JavaMail.zimbra@nod.at> <4fcd272f-81e3-4729-922b-588ad144e39b@app.fastmail.com> In-Reply-To: <4fcd272f-81e3-4729-922b-588ad144e39b@app.fastmail.com> From: Linus Walleij Date: Fri, 12 Sep 2025 14:46:31 +0200 X-Gm-Features: Ac12FXysdXrp8ARxlqs--JPKzGSESzQlXQvRlkFB3ZYER3az5tDF4P1ySurKojc Message-ID: Subject: Re: [TECH TOPIC] Reaching consensus on CONFIG_HIGHMEM phaseout To: Arnd Bergmann Cc: Richard Weinberger , Dave Hansen , ksummit , linux-kernel , linux-arm-kernel , linuxppc-dev , linux-mips , linux-mm , imx , Christophe Leroy , Lucas Stach , Geert Uytterhoeven , Ankur Arora , David Hildenbrand , Mike Rapoport , Lorenzo Stoakes , Matthew Wilcox , Andrew Morton , "Liam R. Howlett" , Vlastimil Babka , Suren Baghdasaryan , Ira Weiny , Nishanth Menon , =?UTF-8?Q?Heiko_St=C3=BCbner?= , Alexander Sverdlin , "Chester A. Unal" , Sergio Paracuellos , Andreas Larsson Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable X-Rspam-User: X-Rspamd-Server: rspam02 X-Rspamd-Queue-Id: 4EFCC80003 X-Stat-Signature: 61hmy1fnrds7hedqqtisw5r688ezjac8 X-HE-Tag: 1757681207-614452 X-HE-Meta: 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 Mtv5/Aws qZM1QhqarxiJRom8KUZtAq8m2ktZR8yGgNyJ7JXHJSrMmfdVegBnwHZ41p4iIjNirgPAa8fGNVV/JOQAe1AfJNNXaoDbJ4QH7UeBv+uHwjKqNb9A2TMX689uYT9uszXjw3c4Vm6aX9ICzw9BiICjyvowjd02GZ6X/n2c9bYoFYG13mtz+GaUoX0Jgxfn26WD76M+TyRYvmMmbFI5wuK7zJPQhS19qPcrKoIBbQADi96XEFVEpi/p1oZm2TUgWjyt939jGY5rCKgcqMKaNECyneuXX/axf3zsbgZ7bJAQeyHUMS0TLC2EkGSTOEGq7KYlGPcebMT/Li4s8LknzGh6u2pA7KViwcGjdNxya7GTHdd2iuAnvzbALLXeO5Q== 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, Sep 12, 2025 at 12:31=E2=80=AFPM Arnd Bergmann wrot= e: > On Wed, Sep 10, 2025, at 22:33, Richard Weinberger wrote: > > ----- Urspr=C3=BCngliche Mail ----- > >> Von: "Dave Hansen" > >>> Even with a new memory split, which could utilize most of the > >>> available memory, I expect there to be issues with various > >>> applications and FPGA device drivers. > > I also remember driver problems on older Marvell NAS systems, which > we never fully figured out, my best guess in retrospect is that these > had devices with DMA address restrictions, and if lowmem is small > enough it would always work, but any lowmem allocation above the > hardware DMA address limit would cause data corruption. This kind of mess is often also driver problems, in the Kirkwood MMC driver there is some dated code traversing sglists iteratively instead of using sg_miter() on !DMA which I think is not entirely safe either. I wanted to fix that driver but the hardware is in my NAS and all the time someone is watching a movie from it :D Yours, Linus Walleij