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Fri, 15 Aug 2025 21:50:17 -0700 (PDT) MIME-Version: 1.0 References: <20250812124941.69508-1-bhe@redhat.com> In-Reply-To: From: Andrey Konovalov Date: Sat, 16 Aug 2025 06:50:06 +0200 X-Gm-Features: Ac12FXxYLTsqomvoG9UG93Lotus4fuW2rcu_NxDqALVSquB40p2BNceICCGi8q4 Message-ID: Subject: Re: [PATCH v2 00/12] mm/kasan: make kasan=on|off work for all three modes To: Baoquan He Cc: linux-mm@kvack.org, ryabinin.a.a@gmail.com, glider@google.com, dvyukov@google.com, vincenzo.frascino@arm.com, akpm@linux-foundation.org, kasan-dev@googlegroups.com, linux-kernel@vger.kernel.org, kexec@lists.infradead.org, sj@kernel.org, lorenzo.stoakes@oracle.com, elver@google.com, snovitoll@gmail.com Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable X-Rspamd-Server: rspam10 X-Rspamd-Queue-Id: 22022140004 X-Stat-Signature: 3rnsuaaskxuptaohqxiba6frtf1uz8bb X-Rspam-User: X-HE-Tag: 1755319818-709280 X-HE-Meta: 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 VpSZEnZk 751q4Ho95dzMpGJkzzoe+6kiyH/mCimSKrXg/Gu10nqOcb4SRPk25T3RcQTxftGcJDb66mc5wkyaepW12XKsV0UJg2IkRaygjVBDbeW0dNiweNpwwHecsWWBAhv8JX8wnmkXcxGHS0JEOiyZMIVm8rbFjXDN9F2v+pKtSx8iwLJ4CGOkGFwcHsYVWLDGdGUF05x84IsdUI/rrY/jYffMZVwNn4TRjHk6BKY0kN2JVFB9zR4wdV8J3dami8y5P87U+ImFxTpS4Qn483GWJzuzVQZ3tiBfs2xDfBrlmx4C5YKS6lsHtviwOAdkaFQRM0uUT1Pbp0LJW3oGNEcruP52JU9DZH0sz0Btd97k3iTnbSOv1VOiJtv+8EW/f4vQpHc9tBIn7KFDsKDMIHSPg2UNruHnwQZhQbnbTPQ5J4xnFYipl9bZthwO42nN8L6grWVzg0VfC 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 Thu, Aug 14, 2025 at 10:56=E2=80=AFAM Baoquan He wrote: > > Ah, I got what you mean. We probably are saying different things. > > In order to record memory content of a corrupted kernel, we need reserve > a memory region during bootup of a normal kernel (usually called 1st > kernel) via kernel parameter crashkernel=3DnMB in advance. Then load > kernel into the crashkernel memory region, that means the region is not > usable for 1st kernel. When 1st kernel collapsed, we stop the 1st kernel > cpu/irq and warmly switch to the loaded kernel in the crashkernel memory > region (usually called kdump kernel). In kdump kernel, it boots up and > enable necessary features to read out the 1st kernel's memory content, > we usually use user space tool like makeudmpfile to filter out unwanted > memory content. > > So this patchset intends to disable KASAN to decrease the crashkernel > meomry value because crashkernel is not usable for 1st kernel. As for > shadow memory of 1st kernel, we need recognize it and filter it away > in makedumpfile. Ah, I see, thank you for the explanation! So kdump kernel runs with the amount of RAM specified by crashkernel=3D. And KASAN's shadow memory increases RAM usage, which means crashkernel=3D needs to be set to a higher value for KASAN kernels. Is my understanding of the problem correct?