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Peter Anvin" , Andy Lutomirski , Peter Zijlstra , Arnaldo Carvalho de Melo , Paolo Bonzini , Arnd Bergmann , Frederic Weisbecker , "Paul E. McKenney" , Jason Baron , Steven Rostedt , Ard Biesheuvel , Sami Tolvanen , "David S. Miller" , Neeraj Upadhyay , Joel Fernandes , Josh Triplett , Boqun Feng , Uladzislau Rezki , Mathieu Desnoyers , Mel Gorman , Andrew Morton , Masahiro Yamada , Han Shen , Rik van Riel , Jann Horn , Dan Carpenter , Oleg Nesterov , Juri Lelli , Clark Williams , Yair Podemsky , Marcelo Tosatti , Daniel Wagner , Petr Tesarik , Shrikanth Hegde Subject: [PATCH v7 05/31] jump_label: Add annotations for validating noinstr usage Date: Fri, 14 Nov 2025 16:01:07 +0100 Message-ID: <20251114150133.1056710-6-vschneid@redhat.com> In-Reply-To: <20251114150133.1056710-1-vschneid@redhat.com> References: <20251114150133.1056710-1-vschneid@redhat.com> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Scanned-By: MIMEDefang 3.0 on 10.30.177.12 X-Rspam-User: X-Rspamd-Server: rspam11 X-Rspamd-Queue-Id: 19312180026 X-Stat-Signature: 4gmd6pcaeads69tzica7im9iugn6sq95 X-HE-Tag: 1763132625-553983 X-HE-Meta: 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 NrDgRkzA lTtZiLvDUXAMl79OybMRW1hEnODEdQ3cY4wt+IErcFV2UNqHzDhPZA7D7vdKM3wI7pWDeR/stRo7t1tZL9vsYMWbCQhCLFoXcZ36KLbvXJ3U6kkcHI2Y2K9AgHejffcHk8hjue2hwfDcksKlK9uT2Y0PX5MAtxgSX28Qs3JxRLSAMxuaVc6c58rm6YQ== 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: From: Josh Poimboeuf Deferring a code patching IPI is unsafe if the patched code is in a noinstr region. In that case the text poke code must trigger an immediate IPI to all CPUs, which can rudely interrupt an isolated NO_HZ CPU running in userspace. Some noinstr static branches may really need to be patched at runtime, despite the resulting disruption. Add DEFINE_STATIC_KEY_*_NOINSTR() variants for those. They don't do anything special yet; that will come later. Signed-off-by: Josh Poimboeuf --- include/linux/jump_label.h | 17 +++++++++++++++++ 1 file changed, 17 insertions(+) diff --git a/include/linux/jump_label.h b/include/linux/jump_label.h index fdb79dd1ebd8c..c4f6240ff4d95 100644 --- a/include/linux/jump_label.h +++ b/include/linux/jump_label.h @@ -388,6 +388,23 @@ struct static_key_false { #define DEFINE_STATIC_KEY_FALSE_RO(name) \ struct static_key_false name __ro_after_init = STATIC_KEY_FALSE_INIT +/* + * The _NOINSTR variants are used to tell objtool the static key is allowed to + * be used in noinstr code. + * + * They should almost never be used, as they prevent code patching IPIs from + * being deferred, which can be problematic for isolated NOHZ_FULL CPUs running + * in pure userspace. + * + * If using one of these _NOINSTR variants, please add a comment above the + * definition with the rationale. + */ +#define DEFINE_STATIC_KEY_TRUE_NOINSTR(name) \ + DEFINE_STATIC_KEY_TRUE(name) + +#define DEFINE_STATIC_KEY_FALSE_NOINSTR(name) \ + DEFINE_STATIC_KEY_FALSE(name) + #define DECLARE_STATIC_KEY_FALSE(name) \ extern struct static_key_false name -- 2.51.0