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[221.241.217.81]) by smtp.gmail.com with ESMTPSA id d9443c01a7336-2e49f7339desm19297455ad.81.2026.10.03.15.39.58 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Sat, 03 Oct 2026 15:40:02 -0700 (PDT) Date: Sun, 04 Oct 2026 07:39:57 +0900 Message-ID: From: Hajime Tazaki To: david@kernel.org Cc: ljs@kernel.org, geert@linux-m68k.org, johannes@sipsolutions.net, linux-mm@kvack.org, liam@infradead.org, rbm@suse.com, akpm@linux-foundation.org, luto@amacapital.net, brendan.jackman@linux.dev, liuhangbin@gmail.com, corbet@lwn.net, kees@kernel.org, broonie@kernel.org, mhocko@suse.com, rppt@kernel.org, shuah@kernel.org, surenb@google.com, vbabka@kernel.org, wad@chromium.org, linux-doc@vger.kernel.org, linux-kselftest@vger.kernel.org, linux-um@lists.infradead.org, daniel@thingy.jp Subject: Re: [PATCH v4 1/2] selftests: run tests on nommu architecture In-Reply-To: References: <20260929235711.2287931-1-thehajime@gmail.com> <20260929235711.2287931-2-thehajime@gmail.com> <94759bed23f00d2044005e36be6f72f297e092f0.camel@sipsolutions.net> User-Agent: Wanderlust/2.15.9 (Almost Unreal) Emacs/27.2 Mule/6.0 MIME-Version: 1.0 (generated by SEMI-EPG 1.14.7 - "Harue") Content-Type: text/plain; charset=US-ASCII X-Rspamd-Server: rspam05 X-Rspamd-Queue-Id: 5F83620002 X-Stat-Signature: bp918m8n8pdapapwwigik74uwdxk9g7m X-Rspam-User: X-HE-Tag: 1791067204-793114 X-HE-Meta: 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 cXniCbH/ +CG4UeG6uHBOUw8VYEOJHB8tOvaH9aup9hrGoMIUMI5nTnvhXFFxhkvduGRpmFMoTMc7WG0vSofxtcmmTC1AF7tAasMWr1a8dtp9Es9nW153FClA9cVlcfk1rbKUaozyfsncSRPTWPBJlPYQ+Azxc59r1KncADehZVloWhbSCdiAnVw9yqWQsTZictVqHa4QJEiGJ2xihVH69xPzmSCvWuTESsPKe1aX9kvn57kxruKJwRewb+Y7sfdfgFQqkw1WNiBZghZkyCaBpx155Ji75xe3LqHQBib0pmX9s2IM8Ga0tKxcUZfLZDxaUUTScZUokJ0c6J9+tQjYut5vz9FoDsz244+OA1SD8IEIW3fUuLHDOmb6di66gMh0CBKQIO9oUtjh5 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: Hello, On Fri, 02 Oct 2026 21:21:53 +0900, David Hildenbrand (Arm) wrote: > > On 10/2/26 13:53, Lorenzo Stoakes (ARM) wrote: > > On Fri, Oct 02, 2026 at 01:38:31PM +0200, Geert Uytterhoeven wrote: > > > >> On Fri, 2 Oct 2026 at 10:10, Lorenzo Stoakes (ARM) wrote: > > > >>> But fork() -> -EINVAL or -ENOSYS = nommu, then just have the child quit and > >>> etc. should do it. > >> > >> fork() is not strictly an MMU-feature (you can implement fork on nommu > >> if all memory accesses are done relative to a base address register), > >> while I think mprotect() is an MMU-feature. Unless it can also be used > >> to change the protection using the one or two BARs most MCU haves? > >> Anything else that is a real MMU-feature? Non-identity mmap()? > > > > Does any nommu arch implement fork() in linux? > > I was about to say, that sounds a bit too theoretical for me. IIUC that is not > implemented, and if someone would propose it we would likely just nak it. > > In the unlikely event that this would see the light of day, we could always > change our detection in the selftests. thanks all for the inputs and review. I will try to implement the detection with /proc/meminfo. -- Hajime