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 vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 30743C4167B for ; Thu, 30 Nov 2023 11:15:27 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1345046AbjK3LPT (ORCPT ); Thu, 30 Nov 2023 06:15:19 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:46546 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231784AbjK3LPR (ORCPT ); Thu, 30 Nov 2023 06:15:17 -0500 Received: from desiato.infradead.org (desiato.infradead.org [IPv6:2001:8b0:10b:1:d65d:64ff:fe57:4e05]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 1CFDBD66; Thu, 30 Nov 2023 03:15:24 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=desiato.20200630; h=In-Reply-To:Content-Type:MIME-Version: References:Message-ID:Subject:Cc:To:From:Date:Sender:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description; bh=Znib/mlXynP7QEaUM1Vt8q5PW5YyGqKpMcVV5Eojr9w=; b=ToH+CX/UgvXhWlmi0wJzixANXZ vA8DFjG6W4jwaVntxBVQUUlnv+MphluAGUPM5JC2AkJRDsYgCeEOmKlInyZXerqgbApIVB0XRPDPd 4pgXT/v5EAN9S37qGe75+0czR6UYDbwMiM240UtqyVPgEwon0Ve5TnFP4PSXtxaexw5Js+xuWypME M4CG9eVG0XQCbTkuQC80GPa6Gb+W76sOBXa+Mm4rAL/sA3VKkh+HEdM8LkI/2Ed9T1cM45J24XeId RR58j2JHrVzHyBsg9u/sMydGIO5589EY5qOTsnt0UtnpE+QdRHrwUXk7/L+qR6rYwza/F47pzLpgU H5eZzCBg==; Received: from j130084.upc-j.chello.nl ([24.132.130.84] helo=noisy.programming.kicks-ass.net) by desiato.infradead.org with esmtpsa (Exim 4.96 #2 (Red Hat Linux)) id 1r8f0p-0012EQ-2q; Thu, 30 Nov 2023 11:15:20 +0000 Received: by noisy.programming.kicks-ass.net (Postfix, from userid 1000) id 31E97300293; Thu, 30 Nov 2023 12:15:19 +0100 (CET) Date: Thu, 30 Nov 2023 12:15:19 +0100 From: Peter Zijlstra To: linux-kernel@vger.kernel.org, Andrew Cooper Cc: linux-tip-commits@vger.kernel.org, Frederic Weisbecker , "Rafael J. Wysocki" , x86@kernel.org Subject: Re: [tip: x86/core] x86: Fix CPUIDLE_FLAG_IRQ_ENABLE leaking timer reprogram Message-ID: <20231130111519.GA20153@noisy.programming.kicks-ass.net> References: <20231115151325.6262-3-frederic@kernel.org> <170126975511.398.12493947150541739641.tip-bot2@tip-bot2> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <170126975511.398.12493947150541739641.tip-bot2@tip-bot2> Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Nov 29, 2023 at 02:55:55PM -0000, tip-bot2 for Peter Zijlstra wrote: > diff --git a/arch/x86/include/asm/mwait.h b/arch/x86/include/asm/mwait.h > index 341ee4f..920426d 100644 > --- a/arch/x86/include/asm/mwait.h > +++ b/arch/x86/include/asm/mwait.h > @@ -124,8 +124,15 @@ static __always_inline void mwait_idle_with_hints(unsigned long eax, unsigned lo > } > > __monitor((void *)¤t_thread_info()->flags, 0, 0); > - if (!need_resched()) > - __mwait(eax, ecx); > + > + if (!need_resched()) { > + if (ecx & 1) { > + __mwait(eax, ecx); > + } else { > + __sti_mwait(eax, ecx); > + raw_local_irq_disable(); > + } > + } Andrew noted that this is only safe if it precludes #DB from happening on mwait, because #DB can wreck the STI shadow thing. > @@ -159,19 +160,13 @@ static __always_inline int __intel_idle(struct cpuidle_device *dev, > static __cpuidle int intel_idle(struct cpuidle_device *dev, > struct cpuidle_driver *drv, int index) > { > + return __intel_idle(dev, drv, index, true); > } > > static __cpuidle int intel_idle_irq(struct cpuidle_device *dev, > struct cpuidle_driver *drv, int index) > { > + return __intel_idle(dev, drv, index, false); > } > > static __cpuidle int intel_idle_ibrs(struct cpuidle_device *dev, > @@ -184,7 +179,7 @@ static __cpuidle int intel_idle_ibrs(struct cpuidle_device *dev, > if (smt_active) > __update_spec_ctrl(0); > > + ret = __intel_idle(dev, drv, index, true); > > if (smt_active) > __update_spec_ctrl(spec_ctrl); > @@ -196,7 +191,7 @@ static __cpuidle int intel_idle_xstate(struct cpuidle_device *dev, > struct cpuidle_driver *drv, int index) > { > fpu_idle_fpregs(); > + return __intel_idle(dev, drv, index, true); > } This is so, because all mwait users should be in __cpuidle section, which itself is part of the noinstr section and as such kprobes/hw-breakpoints etc.. are disallowed. Notable vmlinux.lds.h has: #define NOINSTR_TEXT \ ALIGN_FUNCTION(); \ __noinstr_text_start = .; \ *(.noinstr.text) \ __cpuidle_text_start = .; \ *(.cpuidle.text) \ __cpuidle_text_end = .; \ __noinstr_text_end = .;