From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 9E82CCCA476 for ; Fri, 10 Oct 2025 15:42:23 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20210309; h=Sender:List-Subscribe:List-Help :List-Post:List-Archive:List-Unsubscribe:List-Id:Content-Transfer-Encoding: MIME-Version:References:In-Reply-To:Message-ID:Date:Subject:Cc:To:From: Reply-To:Content-Type:Content-ID:Content-Description:Resent-Date:Resent-From: Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Owner; bh=ypuA88VHIrtZCycTQvLRbp4fTjYOiPnVr/lgVBnkLI0=; b=h4R9sJz/pE5krUOxVEr7cc+sNL lw8yjU1ahRAIXA6a378n8Jiy6NQhXc4doXUrdXIpxpk9vZErGJY7d+4RMeBjvBJPNoWb3nO8VnvR6 4RAx1kNXZEBVw1ctoaX30VTFedkBR5Xf79ypOGHIkCRmO6rtYfwGTXZ2funUzJouUHNWNuClPcGs3 M0xztrm/bVoQaGBkgg6jTrDsXkiWCyoi5huIE66pKQfI90izzz6wwdXKodHWPPVVj+8vMVBhqja3Y Xuk47q4FEUSiEwfCAZTis4L1deK8UVpqhs+Cy94O9HsApb25Tm23bHGQfjzzwk7fwMD8/3c9DmHY0 uBsrpFPw==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.98.2 #2 (Red Hat Linux)) id 1v7FG5-00000008qhq-1Xp5; Fri, 10 Oct 2025 15:42:17 +0000 Received: from us-smtp-delivery-124.mimecast.com ([170.10.129.124]) by bombadil.infradead.org with esmtps (Exim 4.98.2 #2 (Red Hat Linux)) id 1v7FG2-00000008qeT-4BRF for linux-arm-kernel@lists.infradead.org; Fri, 10 Oct 2025 15:42:16 +0000 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1760110934; 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=Z76DB5RAPbg5rvxKWUGJXUcpGlQAUMFN8c9MPiNNGKro7L34g+Sm2TqMFc+4KgBnCLsgMe fRSRTRU2VYfAEKdQf6DuR20/PEZubF9To9BdCGiQYJeq9MC5C0rH7ULhkRXyRBf1oVtq4y Fe9hIIZ39h7clgOHg9xbsEvqCqIdc+c= Received: from mx-prod-mc-01.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-691-7bEM6FEUOcOziUsCCagKng-1; Fri, 10 Oct 2025 11:42:10 -0400 X-MC-Unique: 7bEM6FEUOcOziUsCCagKng-1 X-Mimecast-MFC-AGG-ID: 7bEM6FEUOcOziUsCCagKng_1760110923 Received: from mx-prod-int-08.mail-002.prod.us-west-2.aws.redhat.com (mx-prod-int-08.mail-002.prod.us-west-2.aws.redhat.com [10.30.177.111]) (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-01.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id 5A5C2195609D; Fri, 10 Oct 2025 15:42:03 +0000 (UTC) Received: from vschneid-thinkpadt14sgen2i.remote.csb (unknown [10.45.224.29]) by mx-prod-int-08.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id 9EFB11800576; Fri, 10 Oct 2025 15:41:47 +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 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-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20251010_084215_109289_F4D152CA X-CRM114-Status: GOOD ( 17.11 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org 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