From nobody Mon Dec 29 18:10:29 2025 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 12D84C61D97 for ; Fri, 24 Nov 2023 22:32:49 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229575AbjKXWck (ORCPT ); Fri, 24 Nov 2023 17:32:40 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:54846 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230074AbjKXWch (ORCPT ); Fri, 24 Nov 2023 17:32:37 -0500 Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 5756810FB for ; Fri, 24 Nov 2023 14:32:44 -0800 (PST) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 90621C433C7; Fri, 24 Nov 2023 22:32:41 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1700865164; bh=CXS0kf7QfS6H/bXiY0zJwq5tEcqIiy9tCvQovQrbkN4=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=HPa6VZmhmx1d/lcTIANzys+lP9tpG585RQPkJGTDl5qaYFfx4ng4+D3Ue51VjCGVl +YxcXCxqvYdyVGph2cL4+kMGm5zFSgpCHg5EBFOVd/8zwyRWjqOFBk6snNRHBTH1wR OFJBStdXapHsWXqoti/A4nXAHrp8NESBWDq5BJBGYQ1eOE1jlVlHkg3NaSap/6tNoS yb6GgWzrn1W2nuFIxs8TJFNr334MzPXjLxHCmzBN3R1FFILiFAcXnSztVzBPWlNXWN N/zdiw303k4a4e8NdAGfP9X1Loxo+a/jrmE/Qe/uz4Z/Bq5ZE758VybQJPlKasDCZI V7UcKca+vdGMQ== From: Frederic Weisbecker To: LKML Cc: Peter Zijlstra , "Rafael J . Wysocki" , Daniel Lezcano , linux-pm@vger.kernel.org, Thomas Gleixner , Ingo Molnar , Borislav Petkov , Dave Hansen , Frederic Weisbecker Subject: [PATCH 1/7] x86: Fix CPUIDLE_FLAG_IRQ_ENABLE leaking timer reprogram Date: Fri, 24 Nov 2023 23:32:20 +0100 Message-ID: <20231124223226.24249-2-frederic@kernel.org> X-Mailer: git-send-email 2.42.1 In-Reply-To: <20231124223226.24249-1-frederic@kernel.org> References: <20231124223226.24249-1-frederic@kernel.org> MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Type: text/plain; charset="utf-8" From: Peter Zijlstra intel_idle_irq() re-enables IRQs very early. As a result, an interrupt may fire before mwait() is eventually called. If such an interrupt queues a timer, it may go unnoticed until mwait returns and the idle loop handles the tick re-evaluation. And monitoring TIF_NEED_RESCHED doesn't help because a local timer enqueue doesn't set that flag. The issue is mitigated by the fact that this idle handler is only invoked for shallow C-states when, presumably, the next tick is supposed to be close enough. There may still be rare cases though when the next tick is far away and the selected C-state is shallow, resulting in a timer getting ignored for a while. Fix this with using sti_mwait() whose IRQ-reenablement only triggers upon calling mwait(), dealing with the race while keeping the interrupt latency within acceptable bounds. Fixes: c227233ad64c (intel_idle: enable interrupts before C1 on Xeons) Signed-off-by: Peter Zijlstra Acked-by: Rafael J. Wysocki Signed-off-by: Frederic Weisbecker --- arch/x86/include/asm/mwait.h | 11 +++++++++-- drivers/idle/intel_idle.c | 19 +++++++------------ 2 files changed, 16 insertions(+), 14 deletions(-) diff --git a/arch/x86/include/asm/mwait.h b/arch/x86/include/asm/mwait.h index 778df05f8539..bae83810505b 100644 --- a/arch/x86/include/asm/mwait.h +++ b/arch/x86/include/asm/mwait.h @@ -115,8 +115,15 @@ static __always_inline void mwait_idle_with_hints(unsi= gned long eax, unsigned lo } =20 __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(); + } + } } current_clr_polling(); } diff --git a/drivers/idle/intel_idle.c b/drivers/idle/intel_idle.c index dcda0afecfc5..3e01a6b23e75 100644 --- a/drivers/idle/intel_idle.c +++ b/drivers/idle/intel_idle.c @@ -131,11 +131,12 @@ static unsigned int mwait_substates __initdata; #define MWAIT2flg(eax) ((eax & 0xFF) << 24) =20 static __always_inline int __intel_idle(struct cpuidle_device *dev, - struct cpuidle_driver *drv, int index) + struct cpuidle_driver *drv, + int index, bool irqoff) { struct cpuidle_state *state =3D &drv->states[index]; unsigned long eax =3D flg2MWAIT(state->flags); - unsigned long ecx =3D 1; /* break on interrupt flag */ + unsigned long ecx =3D 1*irqoff; /* break on interrupt flag */ =20 mwait_idle_with_hints(eax, ecx); =20 @@ -159,19 +160,13 @@ static __always_inline int __intel_idle(struct cpuidl= e_device *dev, static __cpuidle int intel_idle(struct cpuidle_device *dev, struct cpuidle_driver *drv, int index) { - return __intel_idle(dev, drv, index); + return __intel_idle(dev, drv, index, true); } =20 static __cpuidle int intel_idle_irq(struct cpuidle_device *dev, struct cpuidle_driver *drv, int index) { - int ret; - - raw_local_irq_enable(); - ret =3D __intel_idle(dev, drv, index); - raw_local_irq_disable(); - - return ret; + return __intel_idle(dev, drv, index, false); } =20 static __cpuidle int intel_idle_ibrs(struct cpuidle_device *dev, @@ -184,7 +179,7 @@ static __cpuidle int intel_idle_ibrs(struct cpuidle_dev= ice *dev, if (smt_active) __update_spec_ctrl(0); =20 - ret =3D __intel_idle(dev, drv, index); + ret =3D __intel_idle(dev, drv, index, true); =20 if (smt_active) __update_spec_ctrl(spec_ctrl); @@ -196,7 +191,7 @@ static __cpuidle int intel_idle_xstate(struct cpuidle_d= evice *dev, struct cpuidle_driver *drv, int index) { fpu_idle_fpregs(); - return __intel_idle(dev, drv, index); + return __intel_idle(dev, drv, index, true); } =20 /** --=20 2.42.1