From patchwork Thu Sep 29 18:07:28 2022 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: "Paul E. McKenney" X-Patchwork-Id: 12994531 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 vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id B7A12C433F5 for ; Thu, 29 Sep 2022 18:07:40 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S235442AbiI2SHj (ORCPT ); Thu, 29 Sep 2022 14:07:39 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:57412 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S235386AbiI2SHg (ORCPT ); Thu, 29 Sep 2022 14:07:36 -0400 Received: from ams.source.kernel.org (ams.source.kernel.org [145.40.68.75]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id B3BB31BEA55; Thu, 29 Sep 2022 11:07:35 -0700 (PDT) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by ams.source.kernel.org (Postfix) with ESMTPS id 5ED36B82643; Thu, 29 Sep 2022 18:07:34 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 14238C43470; Thu, 29 Sep 2022 18:07:33 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1664474853; bh=ngiy42v1jAmn2gtQrSvCJSPS7F9XoJDfjE9vMtSui1I=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=W5/DUILQkSvnoRthJ6xnXz11AbPVfjVdJTyWh9g3b0ai50uMKDknpbFt0TJB+sU65 plKrwfDqhp6z2tXa4+TQg+RaWS5y/r4Hf+sUUDfNBasetOvBjY5EHflaU5CyfHog5U yPt8GHMoufErHzelv96yf4IxtmyVPvMw2Qpo4bhM2W4uGtOj0E8O9Wl+CK1SuZM+dg raX1qmHOCPiADfzoeg/Suj/CE6sEw7OdeonMnOtDz1In5Vr1psX8MjxcwNHi+f4XYt 5W0bu0ji1GyR7cd6bJLm61LHazEuxuy9gu5zhHliDvQbDV4YtLFK+1/wB0wbzFGkCb dKPtZIqUVTuDw== Received: by paulmck-ThinkPad-P17-Gen-1.home (Postfix, from userid 1000) id B2D195C0DE5; Thu, 29 Sep 2022 11:07:32 -0700 (PDT) From: "Paul E. McKenney" To: rcu@vger.kernel.org Cc: linux-kernel@vger.kernel.org, kernel-team@fb.com, rostedt@goodmis.org, "Paul E. McKenney" , Thomas Gleixner , Ingo Molnar , Borislav Petkov , Dave Hansen , "H. Peter Anvin" , John Ogness , Petr Mladek , x86@kernel.org Subject: [PATCH RFC v2 rcu 5/8] arch/x86: Add ARCH_HAS_NMI_SAFE_THIS_CPU_OPS Kconfig option Date: Thu, 29 Sep 2022 11:07:28 -0700 Message-Id: <20220929180731.2875722-5-paulmck@kernel.org> X-Mailer: git-send-email 2.31.1.189.g2e36527f23 In-Reply-To: <20220929180714.GA2874192@paulmck-ThinkPad-P17-Gen-1> References: <20220929180714.GA2874192@paulmck-ThinkPad-P17-Gen-1> MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: rcu@vger.kernel.org The x86 architecture uses an add-to-memory instruction to implement this_cpu_add(), which is NMI safe. This means that the old and more-efficient srcu_read_lock() may be used in NMI context, without the need for srcu_read_lock_nmisafe(). Therefore, add the new Kconfig option ARCH_HAS_NMI_SAFE_THIS_CPU_OPS to arch/x86/Kconfig, which will cause NEED_SRCU_NMI_SAFE to be deselected, thus preserving the current srcu_read_lock() behavior. Link: https://lore.kernel.org/all/20220910221947.171557773@linutronix.de/ Signed-off-by: Paul E. McKenney Cc: Thomas Gleixner Cc: Ingo Molnar Cc: Borislav Petkov Cc: Dave Hansen Cc: "H. Peter Anvin" Cc: John Ogness Cc: Petr Mladek Cc: --- arch/x86/Kconfig | 1 + 1 file changed, 1 insertion(+) diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig index f9920f1341c8..ee5783d8ec71 100644 --- a/arch/x86/Kconfig +++ b/arch/x86/Kconfig @@ -81,6 +81,7 @@ config X86 select ARCH_HAS_KCOV if X86_64 select ARCH_HAS_MEM_ENCRYPT select ARCH_HAS_MEMBARRIER_SYNC_CORE + select ARCH_HAS_NMI_SAFE_THIS_CPU_OPS select ARCH_HAS_NON_OVERLAPPING_ADDRESS_SPACE select ARCH_HAS_PMEM_API if X86_64 select ARCH_HAS_PTE_DEVMAP if X86_64