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AJvYcCV+FQrJQQXyTzsGKGUw0xwnQy7dFcbCrplYTIgmTOs12Z+Shc8ejFO6kX9Sd5xCSJ6xkxqphUSU0h/ZMwo5Gl1ahGw= X-Gm-Message-State: AOJu0Yz3dPoK8i9ow04opc5NDVCAdALE3XmDKuuNYlGs1AfTtLknpQnt 308RPSl5I2MF3D7hjpJHVN75TQoDKrcSSp1df7h6vO+Wtc7z2EHpiiasu/GAlDxT4wtaLCHfGnw GDpZ7a6oQtsJcdLUUPvSLDwV/hAiSDyUGJ09z X-Google-Smtp-Source: AGHT+IG4JaLnVUVMywHgKWR5RLAZx4PZdexzuK6i5qlGKBVjqac751o/32budwVfajonH+PxBsa2bq093K+sijHFr4Y= X-Received: by 2002:a0c:8e47:0:b0:6b0:7864:90ac with SMTP id 6a1803df08f44-6b2afc6efb7mr135971756d6.11.1718721512230; Tue, 18 Jun 2024 07:38:32 -0700 (PDT) MIME-Version: 1.0 References: <20240613153924.961511-1-iii@linux.ibm.com> <20240613153924.961511-15-iii@linux.ibm.com> In-Reply-To: <20240613153924.961511-15-iii@linux.ibm.com> From: Alexander Potapenko Date: Tue, 18 Jun 2024 16:37:55 +0200 Message-ID: Subject: Re: [PATCH v4 14/35] kmsan: Do not round up pg_data_t size To: Ilya Leoshkevich Cc: Alexander Gordeev , Andrew Morton , Christoph Lameter , David Rientjes , Heiko Carstens , Joonsoo Kim , Marco Elver , Masami Hiramatsu , Pekka Enberg , Steven Rostedt , Vasily Gorbik , Vlastimil Babka , Christian Borntraeger , Dmitry Vyukov , Hyeonggon Yoo <42.hyeyoo@gmail.com>, kasan-dev@googlegroups.com, linux-kernel@vger.kernel.org, linux-mm@kvack.org, linux-s390@vger.kernel.org, linux-trace-kernel@vger.kernel.org, Mark Rutland , Roman Gushchin , Sven Schnelle Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable X-Rspamd-Queue-Id: 49E3D1C000B X-Stat-Signature: efsgy1x1no1j87ruaao5zf5xaidehk57 X-Rspamd-Server: rspam09 X-Rspam-User: X-HE-Tag: 1718721513-751335 X-HE-Meta: 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 un9//zI3 UkDQBPM0L+gEquwi4J+gWuCaKv7c4tQI+IK7lqUag0UeKWva34jb3SgwnvzpkK6Xvdm74ByItIeK+w6DC9/RtrroslqMkNnIH+97QtfG5IwCq8+meFvfDSsZrNBi5n+QTHqmC59wf2+fZIW5NG3HVkOcidKAETufY8pXMZiW8dSsNvtinvNC0r2rsS+NfjCDaC6iA9tAJCpX1bMlxXxjk8vusLfsQRULTcAs/le0UjfBWFgq8lVP2fNR/mGYjUL0tgqO68uUfzRCGL5U+dBBe7DzcoDShvaObQ5OG5S1g80vKN5khR+HrZiJwJHBS9Pt8RtoegQT4j/Fl6haMyTsufwR6kg== X-Bogosity: Ham, tests=bogofilter, spamicity=0.064627, 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 Thu, Jun 13, 2024 at 5:39=E2=80=AFPM Ilya Leoshkevich wrote: > > x86's alloc_node_data() rounds up node data size to PAGE_SIZE. It's not > explained why it's needed, but it's most likely for performance > reasons, since the padding bytes are not used anywhere. Some other > architectures do it as well, e.g., mips rounds it up to the cache line > size. > > kmsan_init_shadow() initializes metadata for each node data and assumes > the x86 rounding, which does not match other architectures. This may > cause the range end to overshoot the end of available memory, in turn > causing virt_to_page_or_null() in kmsan_init_alloc_meta_for_range() to > return NULL, which leads to kernel panic shortly after. > > Since the padding bytes are not used, drop the rounding. Nice catch, thanks! > Signed-off-by: Ilya Leoshkevich Reviewed-by: Alexander Potapenko