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AJvYcCWasmq5n8/tzRXWYFDegQ5NR+4BInIouIb5wPp9hOr68Xfm6c+OisWLWWFgvOrFXESqw6oFTmR1GQ==@kvack.org X-Gm-Message-State: AOJu0YwGiB8UXtUqfMyJnI3+vnJSbwMelTKNTwjUnV6+PYk40kk53Z48 FIc0JlzvmZW5hkXQQDg2Ct2zY/HzSl4kM4Exau2ZTjqujD5G67w2vGGJr1TRu0krLq4TRaZz7RS 7AScR94QuQe7IkIeozvX8bioC1GrYtXLeB906qYVv X-Gm-Gg: ASbGncsKij8eBexQ3k/d6kbiNMy7QFhJL1IiYcBtylAgBTRIJrKRiw3t4u/zdy70Uxi bPgNPUa8lvna4JRTWxuo+8NQu7idFJYzMtC8SI/r5ys+Z/eNqp3ZHZcWZrXiUm7YMhJPjL4MLGp /pO2sjQuS1t7A8ijJRNAR8D8mMMwsWsdj3F1uMhjzYgFKp7jte8Jkz3LEKTIkW2whIRdKGPW5Np XIa0g5I1s7gALR7AbzJHJ+ikWxtc5rgs5jEJuYpkKBnDt+IdwzrXW67jBInVX8W/KT18RDM8+RQ PN0+62ZydnsyRwY= X-Google-Smtp-Source: AGHT+IGMcx4JTyoiLXSjiI5ZnYiFYQ0QhaKKSOD4lt9orRKK4hn4fiBcmRwDE/b5ad2H8h/ilMH/9HIGo1JwDkoM2ac= X-Received: by 2002:a05:6214:dc1:b0:87f:fecf:17b2 with SMTP id 6a1803df08f44-8817678f534mr37024656d6.64.1762522362918; Fri, 07 Nov 2025 05:32:42 -0800 (PST) MIME-Version: 1.0 References: <20251106160845.1334274-2-aleksei.nikiforov@linux.ibm.com> <20251106160845.1334274-6-aleksei.nikiforov@linux.ibm.com> <20251107104926.17578C07-hca@linux.ibm.com> In-Reply-To: <20251107104926.17578C07-hca@linux.ibm.com> From: Alexander Potapenko Date: Fri, 7 Nov 2025 14:32:06 +0100 X-Gm-Features: AWmQ_blqrF6qkYIlKEriMvS8QB3DM2vAveh3NdlyDLE92dPFiq1osVICbBllaDE Message-ID: Subject: Re: [PATCH 2/2] s390/fpu: Fix kmsan in fpu_vstl function To: Heiko Carstens Cc: Aleksei Nikiforov , 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 Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable X-Rspamd-Queue-Id: 38EF31C000B X-Rspamd-Server: rspam07 X-Stat-Signature: ejcmd6e5oam449aoc5ymxqbci3h8owmi X-Rspam-User: X-HE-Tag: 1762522364-701413 X-HE-Meta: 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 D2eFHERY w1o5U+nLu6QncgjXb9GY8AZQ+s4lMi44UC2W9Ys2bW4oKWeEl9mGJjSIsVxbtFlbpNGwLN+PIGkJ+MJKwQDrBjDqhYlIa6VOCXeO5tozkAaEPMTSYFF2orPEoIc5A8JKqLhXu8DkSoTwiYfhkOfQ16GfaCZW3ykyKin97sm8Rwk1r9KEb26HrDCW/T6dbDrQW7GI+PYzkpKOSbWYCcx6JDV4XrDBLcnVUD7qXFZWHAztpN1beVQ+EVQ1IKl2o3ffyhxfx2+OGWP0svNw= X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Fri, Nov 7, 2025 at 11:49=E2=80=AFAM Heiko Carstens = wrote: > > On Fri, Nov 07, 2025 at 11:26:50AM +0100, Alexander Potapenko wrote: > > On Thu, Nov 6, 2025 at 5:09=E2=80=AFPM Aleksei Nikiforov > > wrote: > > > @@ -409,6 +410,7 @@ static __always_inline void fpu_vstl(u8 v1, u32 i= ndex, const void *vxr) > > > : [vxr] "=3DR" (*(u8 *)vxr) > > > : [index] "d" (index), [v1] "I" (v1) > > > : "memory", "1"); > > > + instrument_write_after(vxr, size); > > > } > > > > Wouldn't it be easier to just call kmsan_unpoison_memory() here directl= y? > > 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 id= ea. 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. --=20 Alexander Potapenko Software Engineer Google Germany GmbH Erika-Mann-Stra=C3=9Fe, 33 80636 M=C3=BCnchen Gesch=C3=A4ftsf=C3=BChrer: Paul Manicle, Liana Sebastian Registergericht und -nummer: Hamburg, HRB 86891 Sitz der Gesellschaft: Hamburg