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b=ddGyknup29KvGfQGIfEwqFGZ1d4WWXQIGRtrE9OBzjxL9Xd5BK3gttkewgrGTwbiL NSk8Zcv3meMLAjy0eCgXXMtcGhvakuD2PtTuuiPL5xd9U6yhj3uWoReue0sc05+ZVV 9Fos/z1NtDQJGC2dZCMRTg7VozDKZqjrye+LSnwqd22EHIsaWMzAYs+Y9tZzTujqTb 3M2/1Ivgo4ZY0qHAHmGFoqX6ixQRbeLA6bIToa4Wm4Dh3db/n/585AZFwIigaeQFxN 3T3p1A92MU030ioQLguXyDW+g2niZAtU5QtzovFMDS2PpF0W/nHjlatlwL+SdrRFpk GKw2afA4K4BxA== Message-ID: <1d49594c-3549-482d-8c11-fdeb2051e952@kernel.org> Date: Tue, 14 Jul 2026 15:03:28 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [RFC PATCH 02/34] ARM: mm: make 2-level pgd_t a scalar To: David Laight , Yeoreum Yun Cc: linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, loongarch@lists.linux.dev, linux-mips@vger.kernel.org, linux-arch@vger.kernel.org, kvm-riscv@lists.infradead.org, linux-riscv@lists.infradead.org, x86@kernel.org, linux-mm@kvack.org, kasan-dev@googlegroups.com, linux-csky@vger.kernel.org, linux-m68k@lists.linux-m68k.org, linux-openrisc@vger.kernel.org, linux@armlinux.org.uk, akpm@linux-foundation.org, ankur.a.arora@oracle.com, rppt@kernel.org, linmag7@gmail.com, chleroy@kernel.org, klarasmodin@gmail.com, chenhuacai@kernel.org, kernel@xen0n.name, kas@kernel.org, zhangtianyang@loongson.cn, wangyuli@aosc.io, tsbogend@alpha.franken.de, ljs@kernel.org, jgg@ziepe.ca, catalin.marinas@arm.com, will@kernel.org, arnd@arndb.de, ryan.roberts@arm.com, pasha.tatashin@soleen.com, rmclure@linux.ibm.com, baolin.wang@linux.alibaba.com, tj@kernel.org, kevin.brodsky@arm.com, anup@brainfault.org, atish.patra@linux.dev, pjw@kernel.org, palmer@dabbelt.com, aou@eecs.berkeley.edu, alex@ghiti.fr, dave.hansen@linux.intel.com, luto@kernel.org, peterz@infradead.org, tglx@kernel.org, mingo@redhat.com, bp@alien8.de, hpa@zytor.com, hannes@cmpxchg.org, mhocko@kernel.org, qi.zheng@linux.dev, shakeel.butt@linux.dev, kasong@tencent.com, baohua@kernel.org, axelrasmussen@google.com, yuanchu@google.com, weixugc@google.com, ryabinin.a.a@gmail.com, glider@google.com, andreyknvl@gmail.com, dvyukov@google.com, vincenzo.frascino@arm.com, anshuman.khandual@arm.com, yang@os.amperecomputing.com, chaitanyas.prakash@arm.com, ardb@kernel.org, guoren@kernel.org, yang.li85200@gmail.com, viro@zeniv.linux.org.uk, dinguyen@kernel.org, schuster.simon@siemens-energy.com, wangruikang@iscas.ac.cn, junhui.liu@pigmoral.tech, muchun.song@linux.dev, vishal.moola@gmail.com, namcao@linutronix.de, pavel@kernel.org, djbw@kernel.org, yu-cheng.yu@intel.com, baolu.lu@linux.intel.com, Jonathan.Cameron@huawei.com, coxu@redhat.com, andreas@gaisler.com, liam@infradead.org, vbabka@kernel.org, surenb@google.com, mhocko@suse.com, geert@linux-m68k.org, shorne@gmail.com, jonas@southpole.se, stefan.kristiansson@saunalahti.fi References: <20260713135614.1618183-1-yeoreum.yun@arm.com> <20260713135614.1618183-3-yeoreum.yun@arm.com> <20260714133415.78e25654@pumpkin> From: "David Hildenbrand (Arm)" Content-Language: en-US Autocrypt: addr=david@kernel.org; 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charset=UTF-8 Content-Transfer-Encoding: 7bit X-Rspamd-Queue-Id: 1F4AE180011 X-Stat-Signature: adgtuy9bp7tywyr4fny5ng9qqpqc6gqi X-Rspam-User: X-Rspamd-Server: rspam12 X-HE-Tag: 1784034225-244675 X-HE-Meta: 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 bBr76j3l zq9PN7nBdndbX7RHEDgxFWpbnMCsxIGobiwI9mzkQzCA7l3ig4OH6s7vyq3o050Av+OpcJPQmuAWP5YxS3s0PEAHsoJkRa49sK0VvujH15tZ3o872PswOH02r3yK/K4XybbFje9sjCcvS9519odGjtAmiBQhODns7Ek2llUAqqkxOFFRehFW55A35lnQCZg/F7TYx8K2UpgDv79OLu/lR/5AYcvW7NyyR098vVv0yt/LFcet2khEubcGaDzI4mn/bauqJ6esRBhKxWyH1cWI1TQFR0RVkGZ8HkEqWLbUGZEgfUaTHcHzaJrxIzl4ePJ6stYvWofQltQbrN9yIyWncdscpFg0FVyH6qo5yBI5Z7hbTs96E2AfZ4QDfYIwW7SCTq0QkaNRKeSS4Yt1deMSzB2uzFeLUiAy9Z4+0bYgjb5i0xxVrwtoVt04bNfkVSg9Kz2Of/szRJAhwtpOwU7M2O8pBnQ== Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On 7/14/26 14:34, David Laight wrote: > On Mon, 13 Jul 2026 14:55:41 +0100 > Yeoreum Yun wrote: > >> From: "David Hildenbrand (Arm)" >> >> We don't want pgd_t to be an array, as it prohibits returning it from a >> function, like pgdp_get(). > > If you use a two element structure the compiler/ABI might be able to > return that from a function in two registers. > That might make the entire mess more readable ... The patch description states: " As an alternative, we could use the STRICT_MM_TYPECHECKS approach here as well, but using an u64 looks conceptually cleaner, even though pgd_val() gets a bit more involved. " Arnd replied on that in more detail. Maybe I should just go back to using bit shifts and handing endianess. -- Cheers, David