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Peter Anvin" , Andy Lutomirski , Peter Zijlstra , Arnaldo Carvalho de Melo , Josh Poimboeuf , 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 18/31] x86/speculation/mds: Mark cpu_buf_idle_clear key as allowed in .noinstr Date: Fri, 14 Nov 2025 16:01:20 +0100 Message-ID: <20251114150133.1056710-19-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-Rspamd-Server: rspam06 X-Rspamd-Queue-Id: 2453B160008 X-Stat-Signature: kbcf986eb43z95jixi8tr4sujtshoaio X-Rspam-User: X-HE-Tag: 1763132812-764669 X-HE-Meta: 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 x3EZLaT1 BE6lDI7xcmIUTLQK3LtR7WGhLxU6QX+sF0DJmiFsHMwJbP2fII3t10tTHZYSs0pR4mQYxjcJ2lfgnrbvUNpbYRwDcfKB7X00u6tGJbcHuRj9fHKAjtg+x5rDOTi4c2KU2wUx6OUd9kg/FRmFVR/nHRbwPrQ1BJ/wluOv34SwPcm3ZYV8VgdSqv5RTl7G6XKQW8sQVOQkG5dQ1lYT6v8byem7Dq0mGrsqtXakCShdFcDehlqxfsZ6gQj6fg9SYXhR34SgPSVJQXdGKFyD333/pZuOIqs887u4h90tL5ZVbPDFxTqR1zNZp2weTPe07bhn00Zzm6u9ovioI6RckOkPwOXlBHIa+sSzCiC4ni4yQYYO2+0o40m+1kke6Y/Mrdgt+YGf9+Svq38Btin4IyccLMkbiX23dhVJMR0aetUG1oJBwvBXkymdseYRe220iybr0IR1G0XGZ/QVly1WbjbCNe74eVLpUk46x6K8w 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: Later commits will cause objtool to warn about static keys being used in .noinstr sections in order to safely defer instruction patching IPIs targeted at NOHZ_FULL CPUs. cpu_buf_idle_clear is used in .noinstr code, and can be modified at runtime (SMT hotplug). Suppressing the text_poke_sync() IPI has little benefits for this key, as hotplug implies eventually going through takedown_cpu() -> stop_machine_cpuslocked() which is going to cause interference on all online CPUs anyway. Mark it to let objtool know not to warn about it. Signed-off-by: Valentin Schneider --- arch/x86/kernel/cpu/bugs.c | 9 +++++++-- 1 file changed, 7 insertions(+), 2 deletions(-) diff --git a/arch/x86/kernel/cpu/bugs.c b/arch/x86/kernel/cpu/bugs.c index a2d7dc4d2a4a3..39f6a2f9593f8 100644 --- a/arch/x86/kernel/cpu/bugs.c +++ b/arch/x86/kernel/cpu/bugs.c @@ -181,8 +181,13 @@ DEFINE_STATIC_KEY_FALSE(switch_mm_always_ibpb); DEFINE_STATIC_KEY_FALSE(switch_vcpu_ibpb); EXPORT_SYMBOL_GPL(switch_vcpu_ibpb); -/* Control CPU buffer clear before idling (halt, mwait) */ -DEFINE_STATIC_KEY_FALSE(cpu_buf_idle_clear); +/* + * Control CPU buffer clear before idling (halt, mwait) + * + * NOINSTR: This static key is updated during SMT hotplug which itself already + * causes some interference. + */ +DEFINE_STATIC_KEY_FALSE_NOINSTR(cpu_buf_idle_clear); EXPORT_SYMBOL_GPL(cpu_buf_idle_clear); /* -- 2.51.0