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Received: from authenticated user by stravinsky.debian.org with esmtpsa (TLS1.3:ECDHE_X25519__RSA_PSS_RSAE_SHA256__AES_256_GCM:256) (Exim 4.94.2) (envelope-from ) id 1vOZv4-004zti-U0; Thu, 27 Nov 2025 11:12:15 +0000 Date: Thu, 27 Nov 2025 03:12:10 -0800 From: Breno Leitao To: Andrew Morton 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: References: <20251126-kfence-v1-1-5a6e1d7c681c@debian.org> <20251126101453.3ba9b3184aa6dd3c718287e6@linux-foundation.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20251126101453.3ba9b3184aa6dd3c718287e6@linux-foundation.org> X-Debian-User: leitao X-Stat-Signature: tgu945rqz41namhcc3ak9if7415tfa8u X-Rspam-User: X-Rspamd-Queue-Id: C135D140007 X-Rspamd-Server: rspam09 X-HE-Tag: 1764241940-438211 X-HE-Meta: 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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 Wed, Nov 26, 2025 at 10:14:53AM -0800, Andrew Morton wrote: > 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. This infrastructure showed up when kfence was created, so, a possible Fixes: target would point to commit 0ce20dd84089 ("mm: add Kernel Electric-Fence infrastructure")