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b=p7X5qj2Ogw6DhSG+Db57ZmeCGAeKCNEcijtsjxrFozJXgGhSqVSUuMUw7Hny7oktD DGvCr7OzgAxHGT0C494t7VZdZ3M5DlMEOAongOWa/1BsSg+h9+f/6eJ0omjCtdMfJv lB77JHtJjrQ3Cv2HxJUD6A+l7gizCooLwhU2WEFM= Date: Wed, 26 Nov 2025 10:14:53 -0800 From: Andrew Morton To: Breno Leitao Cc: Alexander Potapenko , Marco Elver , Dmitry Vyukov , kasan-dev@googlegroups.com, linux-mm@kvack.org, linux-kernel@vger.kernel.org, kernel-team@meta.com Subject: Re: [PATCH] mm/kfence: add reboot notifier to disable KFENCE on shutdown Message-Id: <20251126101453.3ba9b3184aa6dd3c718287e6@linux-foundation.org> In-Reply-To: <20251126-kfence-v1-1-5a6e1d7c681c@debian.org> References: <20251126-kfence-v1-1-5a6e1d7c681c@debian.org> X-Mailer: Sylpheed 3.8.0beta1 (GTK+ 2.24.33; x86_64-pc-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit X-Rspamd-Server: rspam12 X-Rspam-User: X-Rspamd-Queue-Id: 9B68A20006 X-Stat-Signature: i6qrodaent64uom8haekyipsneizct5d X-HE-Tag: 1764180895-841732 X-HE-Meta: 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 zvNHm7iR eTB7zxpMtA4hNpkf0RQiLrBoir2xp5WN8nbscJfMRSXZ3njnZz10lyDmYznb8e6sjqV2SMqrJ6kH8i1e+7h+p0zJOzIhBjz5Tfce/X4vUrGiE9xn0RR0O/CJE/aQTyeLR2aTlBDONgymSD+ZgGzlZ6cLQtCgo17J9beoPBqLALiaF3zcIiBE18NSggwN29AfrCGUYw1SLl4d2KfxPhcYbDTW5MVv72RlLjr2tcEcy7SoLfsFLP9Sb+vCHOYyGsDw1AKevtccPpEQKcVwIb3ZoLYzbTPVnNraYeBGf0weRpfmTTzs= 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 Wed, 26 Nov 2025 09:46:18 -0800 Breno Leitao wrote: > During system shutdown, KFENCE can cause IPI synchronization issues if > it remains active through the reboot process. To prevent this, register > a reboot notifier that disables KFENCE and cancels any pending timer > work early in the shutdown sequence. > > This is only necessary when CONFIG_KFENCE_STATIC_KEYS is enabled, as > this configuration sends IPIs that can interfere with shutdown. Without > static keys, no IPIs are generated and KFENCE can safely remain active. > > The notifier uses maximum priority (INT_MAX) to ensure KFENCE shuts > down before other subsystems that might still depend on stable memory > allocation behavior. > > This fixes a late kexec CSD lockup[1] when kfence is trying to IPI a CPU > that is busy in a IRQ-disabled context printing characters to the > console. > > Link: https://lore.kernel.org/all/sqwajvt7utnt463tzxgwu2yctyn5m6bjwrslsnupfexeml6hkd@v6sqmpbu3vvu/ [1] 6.13 kernels and earlier, so I assume we'll want a cc:stable on this. And I assume there's really no identifiable Fixes: target.