From nobody Wed Dec 17 06:10:39 2025 Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.133.124]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 1760B329C5F for ; Fri, 14 Nov 2025 15:03:44 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=170.10.133.124 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1763132626; cv=none; b=hrTZz9h4IBAFa2FGjqKUGZ0WsTBIrEVC9PZ+shLKRvufOfIrtuYNZvbFzbShadw/Uab/6egmC5qdKEUcopEHCoZg6XRdBQTFtsDyfNTXqZUpFcx/QrPFcIfOiOxKXwDHJlm3ZXAPm2kCnBzrCVDDbXrKjZiq3SS9y6IXJfnP7ok= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1763132626; c=relaxed/simple; bh=tUCxDYx2/0NN5QR1DEvZrfPrIv3zYWsV4oVjHSBsnzs=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=mgV4dczKw4zkfHE9Eb/OHS612ACEEds8PahHtI8jKJm+Zia3VHNOPwukzed4NKtdGKDJ0JxTuAVI4wVOKx46HJMRrub2uakHOYBjRBLHqIOhN7COEUY4rSWuZDXw17uqftQy84HyVdsL7zb193LIQwiVUuM5+rwOqdBumtRdiUc= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=redhat.com; spf=pass smtp.mailfrom=redhat.com; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b=BBE3rZCS; arc=none smtp.client-ip=170.10.133.124 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=redhat.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=redhat.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="BBE3rZCS" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1763132624; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=ypuA88VHIrtZCycTQvLRbp4fTjYOiPnVr/lgVBnkLI0=; b=BBE3rZCSc1PsvbM7expgtsu22bcRAFO5tkc2RAY1ZCDkMZHPFibt+xbHXcLw0iLLFOhyOq nDbec7XFNJScVZwtwsfJaTnkfKAqVfrQSlN0tW502o60Y4wPUf2cM4A9nOUCEtHTR1aH+3 kogwAaiTtAu/pWCpA2lwhuL+Hu+7sAo= Received: from mx-prod-mc-03.mail-002.prod.us-west-2.aws.redhat.com (ec2-54-186-198-63.us-west-2.compute.amazonaws.com [54.186.198.63]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_256_GCM_SHA384) id us-mta-504-SKUOVx5hNtSa3DHoze9ZYQ-1; Fri, 14 Nov 2025 10:03:40 -0500 X-MC-Unique: SKUOVx5hNtSa3DHoze9ZYQ-1 X-Mimecast-MFC-AGG-ID: SKUOVx5hNtSa3DHoze9ZYQ_1763132615 Received: from mx-prod-int-03.mail-002.prod.us-west-2.aws.redhat.com (mx-prod-int-03.mail-002.prod.us-west-2.aws.redhat.com [10.30.177.12]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits) server-digest SHA256) (No client certificate requested) by mx-prod-mc-03.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id E500A18D95C7; Fri, 14 Nov 2025 15:03:34 +0000 (UTC) Received: from vschneid-thinkpadt14sgen2i.remote.csb (unknown [10.45.226.10]) by mx-prod-int-03.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id DA7DF1956046; Fri, 14 Nov 2025 15:03:20 +0000 (UTC) From: Valentin Schneider To: linux-kernel@vger.kernel.org, linux-mm@kvack.org, rcu@vger.kernel.org, x86@kernel.org, linux-arm-kernel@lists.infradead.org, loongarch@lists.linux.dev, linux-riscv@lists.infradead.org, linux-arch@vger.kernel.org, linux-trace-kernel@vger.kernel.org Cc: Josh Poimboeuf , Thomas Gleixner , Ingo Molnar , Borislav Petkov , Dave Hansen , "H. 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> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable X-Scanned-By: MIMEDefang 3.0 on 10.30.177.12 Content-Type: text/plain; charset="utf-8" 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 =3D STATIC_KEY_FALSE_INIT =20 +/* + * The _NOINSTR variants are used to tell objtool the static key is allowe= d to + * be used in noinstr code. + * + * They should almost never be used, as they prevent code patching IPIs fr= om + * being deferred, which can be problematic for isolated NOHZ_FULL CPUs ru= nning + * 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 =20 --=20 2.51.0