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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 Subject: [PATCH v6 05/29] jump_label: Add annotations for validating noinstr usage Date: Fri, 10 Oct 2025 17:38:15 +0200 Message-ID: <20251010153839.151763-6-vschneid@redhat.com> In-Reply-To: <20251010153839.151763-1-vschneid@redhat.com> References: <20251010153839.151763-1-vschneid@redhat.com> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Scanned-By: MIMEDefang 3.4.1 on 10.30.177.111 X-Rspamd-Server: rspam10 X-Rspamd-Queue-Id: A698E40012 X-Stat-Signature: sjw3abrbohffucbqz3m3k33983yyn95o X-Rspam-User: X-HE-Tag: 1760110935-848133 X-HE-Meta: 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 6sis5z7R MXKc6NGlPDZ6PBF/NahlDZi6rIUO8SjWSksIOI1P13J84YI3dYmgaThZvR8E5D4gma/WABKN+NtAY7bGfOERXKz6ZhzedridVcaV9piXrl/gzfwcwOmNXG/vPs3S5qjt/VBDOjRNwMDp77i1ip444wcCX2Mr9FZU0O41Ph9ZYmrTZ9wuxnZjSAFGe5g== 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