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Received: by sipsolutions.net with esmtpsa (TLS1.3:ECDHE_X25519__ECDSA_SECP256R1_SHA256__AES_256_GCM:256) (Exim 4.98.2) (envelope-from ) id 1xCDbn-000000001cC-1VvD; Thu, 01 Oct 2026 12:01:47 +0200 Message-ID: <94759bed23f00d2044005e36be6f72f297e092f0.camel@sipsolutions.net> Subject: Re: [PATCH v4 1/2] selftests: run tests on nommu architecture From: Johannes Berg To: "Lorenzo Stoakes (ARM)" , "David Hildenbrand (Arm)" Cc: Hajime Tazaki , 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, geert@linux-m68k.org, daniel@thingy.jp Date: Thu, 01 Oct 2026 12:01:45 +0200 In-Reply-To: References: <20260929235711.2287931-1-thehajime@gmail.com> <20260929235711.2287931-2-thehajime@gmail.com> Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable User-Agent: Evolution 3.60.2 (3.60.2-2.fc44) MIME-Version: 1.0 X-malware-bazaar: not-scanned X-Rspam-User: X-Stat-Signature: 98e7zatwn478c69z9bfbphidc1zfiobx X-Rspamd-Server: rspam11 X-Rspamd-Queue-Id: 72319140011 X-HE-Tag: 1790848914-26455 X-HE-Meta: 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 o7uiBTih vxW+dti6XXVuQAkOU9xG1uEBNdAJzq1e3CgWHFy1Yt03P87O86YWdrWrb3acGsPYDOkacEfwhwb1tk0lYoNiXI7lhXiieUhpC2PeoLV07WpS/R0QkZf3lm3aKBmu9xyOU+2NRS4ZNnB03IhEpsAedZsx2ZK1I8xzm9IeIN0sKcXtg+g2q4ekhUkXufutIYb0TLRHhVoukKfGJrSXBWDAiWCZ2f1sQ24oE5ClTcZ+PF8FR6PGjC41pkbyRzXe/V8OLYzjv Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Thu, 2026-10-01 at 09:42 +0100, Lorenzo Stoakes (ARM) wrote: > On Thu, Oct 01, 2026 at 09:08:33AM +0200, David Hildenbrand (Arm) wrote: > > On 9/30/26 01:57, Hajime Tazaki wrote: > > > Architectures lacking MMU don't support fork(2) syscall and only > > > vfork(2) is available with limitations. Thus, we cannot run kselftes= t > > > on nommu architecture as is. > > >=20 > > > This commit addresses this issue with the following changes: > > >=20 > > > - on test run stage, avoid calling timeout command when NOMMU=3D1 var= iable > > > added to environmental variable, since timeout command uses fork > > > syscall which nommu platform doesn't support. > > > - describe the difference of nommu tests in the document. > > >=20 > > > So command line to build/execute tests for nommu should be like below= : > > >=20 > > > $ make ARCH=3Dum NOMMU=3D1 O=3Dbuild kselftest-all TARGETS=3Dnommu > > > $ make ARCH=3Dum NOMMU=3D1 O=3Dbuild kselftest-install TARGETS=3Dnom= mu > > > $ NOMMU=3D1 ./build/kselftest/kselftest_install/run_kselftest.sh -p = \ > > > -c nommu > >=20 > > Is there a way we could derive that from the environment in one of thes= e cases? >=20 > I thought maybe uname could help but our LLM overlords tell me no. Hajime originally wanted uname to indicate it, but that caused regressions elsewhere, so we dropped that commit. I guess we could put _something_ back? > It pointed at something though. >=20 > In fs/proc/meminfo.c: >=20 > #ifndef CONFIG_MMU > show_val_kb(m, "MmapCopy: ", > (unsigned long)atomic_long_read(&mmap_pages_allocated)); > #endif >=20 > So MmapCopy in /proc/meminfo tells us definitively, weirdly enough. Hyrum's law and all that, but I guess it's not highly likely to (want to) change :) johannes