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Thu, 07 Aug 2025 10:12:52 -0700 (PDT) Received: from [10.214.35.248] ([80.93.240.68]) by smtp.gmail.com with ESMTPSA id 2adb3069b0e04-55b88cae595sm2715631e87.155.2025.08.07.10.12.51 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Thu, 07 Aug 2025 10:12:51 -0700 (PDT) Message-ID: Date: Thu, 7 Aug 2025 19:12:02 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH 0/4] mm/kasan: make kasan=on|off work for all three modes To: Marco Elver , Baoquan He Cc: linux-mm@kvack.org, glider@google.com, andreyknvl@gmail.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 References: <20250805062333.121553-1-bhe@redhat.com> Content-Language: en-US From: Andrey Ryabinin In-Reply-To: Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-Stat-Signature: ycw3hpq5stcsy17x3368p7atqe4rt5to X-Rspam-User: X-Rspamd-Queue-Id: 513124000C X-Rspamd-Server: rspam02 X-HE-Tag: 1754586774-714628 X-HE-Meta: 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 VyCwAqlZ 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 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 8/6/25 9:16 AM, Marco Elver wrote: > On Tue, 5 Aug 2025 at 08:23, 'Baoquan He' via kasan-dev > wrote: >> >> Currently only hw_tags mode of kasan can be enabled or disabled with >> kernel parameter kasan=on|off for built kernel. For kasan generic and >> sw_tags mode, there's no way to disable them once kernel is built. >> This is not convenient sometime, e.g in system kdump is configured. >> When the 1st kernel has KASAN enabled and crash triggered to switch to >> kdump kernel, the generic or sw_tags mode will cost much extra memory >> for kasan shadow while in fact it's meaningless to have kasan in kdump >> kernel. > > Are you using KASAN generic or SW-tags is production? > If in a test environment, is the overhead of the kdump kernel really > unacceptable? > kdump kernel operates with limited amount of memory, whatever was provided in 'crashkernel=' for the primary kernel. So it's quite easily can ran out of memory. By default kdump uses same as currently running kernel, but it can be configured to use a different one. At least in fedora it's in /etc/sysconfig/kdump: $ cat /etc/sysconfig/kdump # Kernel Version string for the -kdump kernel, such as 2.6.13-1544.FC5kdump # If no version is specified, then the init script will try to find a # kdump kernel with the same version number as the running kernel. KDUMP_KERNELVER="" >> So this patchset moves the kasan=on|off out of hw_tags scope and into >> common code to make it visible in generic and sw_tags mode too. Then we >> can add kasan=off in kdump kernel to reduce the unneeded meomry cost for >> kasan. >> >> Test: >> ===== >> I only took test on x86_64 for generic mode, and on arm64 for >> generic, sw_tags and hw_tags mode. All of them works well. > > Does it also work for CONFIG_KASAN_INLINE? > I think it should. Because we don't initialize init_task.kasan_depth we always bail out in kasan_report().