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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-CRM114-Version: 20100106-BlameMichelson ( TRE 0.9.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20261003_154004_159815_88AD5095 X-CRM114-Status: GOOD ( 19.87 ) X-BeenThere: linux-um@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "linux-um" Errors-To: linux-um-bounces+linux-um=archiver.kernel.org@lists.infradead.org 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