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b=pZnf/QTW0b89tenZJtxRPDk9uPa+iHqgqViWgH9ajaHkxJ4DKtUYwocSR8YvvaEd1 /B9LLPkifVtUseT9Jwhp1I5HyRnz627dFVbs1yVLbEvKqYrHE7jzXImjCSwImIw265 +oQtb1WHLE1XEIptM3nown4JQcTBxGza3bm/nBcE= Date: Fri, 20 Mar 2026 13:53:52 -0700 From: Andrew Morton To: Audra Mitchell Cc: david@kernel.org, ljs@kernel.org, Liam.Howlett@oracle.com, vbabka@kernel.org, rppt@kernel.org, surenb@google.com, mhocko@suse.com, shuah@kernel.org, usama.anjum@collabora.com, colin.i.king@gmail.com, avagin@google.com, linux-kselftest@vger.kernel.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH] selftests/mm: Fix soft-dirty kselftest supported check Message-Id: <20260320135352.53cc24edc1ce1666141168f6@linux-foundation.org> In-Reply-To: <20260320184010.759461-2-audra@redhat.com> References: <20260320184010.759461-1-audra@redhat.com> <20260320184010.759461-2-audra@redhat.com> X-Mailer: Sylpheed 3.8.0beta1 (GTK+ 2.24.33; x86_64-pc-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit X-Stat-Signature: nb6c4zoumia5h88xg1nc9bgykx7fbp6r X-Rspam-User: X-Rspamd-Queue-Id: 0B54018000C X-Rspamd-Server: rspam12 X-HE-Tag: 1774040034-277914 X-HE-Meta: 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 ddoQSL94 3+7l1+zXlNMqCcWyz8Ks6iYLN6BeN20cF0sidkpjaclICo+/eXqcce0BHJbUJq9wWdQRFefFp8xLq1XEMDjUh2D/IQTTiIXLoVxRlpdtPH7EHb9YLtVZx8oZNidXZJEvb1TH0WaqxKWEJf2UhqNh6fDxMgsulSOSAPRyEbnwH0HggwMs0bD3NZNE140aROziHhY6JeFs+Vh3vPBLehG4ejb4m1SFt/281ErSy8GMmeCis+dJvlUpZ5DlGzE7uRLDdAd8J0PDxMP5BmdctlN2DTQETm9jb29b4HaF8hqvw7LyqEsR2PZgyS8C/nmzA5//W2utCDztbjH7H5DeJmO5dzxngcZ5gIOnSXl7wGyqdd0nv4mrLVA1cmzEqSC/TYcEEPiSchHtkHXUa9lHk3UBex8d0fQ== Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Fri, 20 Mar 2026 14:39:15 -0400 Audra Mitchell wrote: > On architectures with separate user address space, such as s390 or > those without an MMU, the soft-dirty kselftest may fail when checking > to see if the feature is supported. > > # -------------------- > # running ./soft-dirty > # -------------------- > # TAP version 13 > # 1..15 > # Bail out! PAGEMAP_SCAN succeeded unexpectedly > # # Totals: pass:0 fail:0 xfail:0 xpass:0 skip:0 error:0 > # [FAIL] > not ok 1 soft-dirty # exit=1 > # SUMMARY: PASS=0 SKIP=0 FAIL=1 > > The soft-dirty test will initate an ioctl with the PAGEMAP_SCAN flag with > an invalid address for the page_region. This is done intentionally to > have the ioctl return with an expected EFAULT and with the correct > categories returned. > > However, on architectures with separate user address space, such as s390 or > those without an MMU, the call to __access_ok (used to validate the > variables provided with the ioctl) will always return true and we will not > fail as expected. > > if (IS_ENABLED(CONFIG_ALTERNATE_USER_ADDRESS_SPACE) || > !IS_ENABLED(CONFIG_MMU)) > return true; > > Let's simplify the check for PAGEMAP_SCAN and provide a valid page_region > address so that we get a non-errno return if it is supported. AI review asked some questions about v1: https://sashiko.dev/#/patchset/20260320184010.759461-2-audra%40redhat.com These might have been addressed in this version but without a versioning tag and without a what-i-changed description I find it hard(er) to tell.