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Fri, 7 Nov 2025 15:34:34 GMT Received: from smtpav01.fra02v.mail.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 0097720043; Fri, 7 Nov 2025 15:34:34 +0000 (GMT) Received: from smtpav01.fra02v.mail.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 0222A20040; Fri, 7 Nov 2025 15:34:33 +0000 (GMT) Received: from [9.111.68.113] (unknown [9.111.68.113]) by smtpav01.fra02v.mail.ibm.com (Postfix) with ESMTP; Fri, 7 Nov 2025 15:34:32 +0000 (GMT) Message-ID: <72ec25d5-e077-4a84-9eca-ce886e2aaffb@linux.ibm.com> Date: Fri, 7 Nov 2025 16:33:40 +0100 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH 2/2] s390/fpu: Fix kmsan in fpu_vstl function To: Alexander Potapenko , Heiko Carstens Cc: Marco Elver , Dmitry Vyukov , Andrew Morton , kasan-dev@googlegroups.com, linux-mm@kvack.org, linux-kernel@vger.kernel.org, linux-s390@vger.kernel.org, Vasily Gorbik , Alexander Gordeev , Christian Borntraeger , Sven Schnelle , Thomas Huth , Juergen Christ , Ilya Leoshkevich References: <20251106160845.1334274-2-aleksei.nikiforov@linux.ibm.com> <20251106160845.1334274-6-aleksei.nikiforov@linux.ibm.com> <20251107104926.17578C07-hca@linux.ibm.com> Content-Language: en-US From: Aleksei Nikiforov In-Reply-To: Content-Type: text/plain; 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>>>> + instrument_write_after(vxr, size); >>>> } >>> >>> Wouldn't it be easier to just call kmsan_unpoison_memory() here directly? >> >> I guess that's your call. Looks like we have already a couple of >> kmsan_unpoison_memory() behind inline assemblies. >> >> So I guess we should either continue using kmsan_unpoison_memory() >> directly, or convert all of them to such a new helper. Both works of >> course. What do you prefer? > > Upon reflection, I think adding instrument_write_after() is not the best idea. > For tools like KASAN and KCSAN, every write has the same semantics, > and the instrumentation just notifies the tool that the write > occurred. > For KMSAN, however, writes may affect metadata differently, requiring > us to either poison or unpoison the destination. > In certain special cases, like instrument_get_user() or > instrument_copy_from_user() the semantics are always fixed, but this > is not true for arbitrary writes. > > We could make the new annotation's name more verbose, but it will just > become a synonym of kmsan_unpoison_memory(). > So I suggest sticking with kmsan_unpoison_memory() for now. > > I'll rework changes with that suggestion. Thank you.