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 X-Spam-Level: X-Spam-Status: No, score=-11.8 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI, MENTIONS_GIT_HOSTING,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 91FD1C433EF for ; Sun, 8 Sep 2019 07:07:23 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 76846214DB for ; Sun, 8 Sep 2019 07:07:23 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727284AbfIHHHW (ORCPT ); Sun, 8 Sep 2019 03:07:22 -0400 Received: from Galois.linutronix.de ([193.142.43.55]:50009 "EHLO Galois.linutronix.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726643AbfIHHHV (ORCPT ); Sun, 8 Sep 2019 03:07:21 -0400 Received: from [5.158.153.53] (helo=tip-bot2.lab.linutronix.de) by Galois.linutronix.de with esmtpsa (TLS1.2:DHE_RSA_AES_256_CBC_SHA256:256) (Exim 4.80) (envelope-from ) id 1i6rI3-0006V7-JY; Sun, 08 Sep 2019 09:07:15 +0200 Received: from [127.0.1.1] (localhost [IPv6:::1]) by tip-bot2.lab.linutronix.de (Postfix) with ESMTP id ED03A1C072D; Sun, 8 Sep 2019 09:07:14 +0200 (CEST) Date: Sun, 08 Sep 2019 07:07:14 -0000 From: "tip-bot2 for Jan Stancek" Reply-to: linux-kernel@vger.kernel.org To: linux-tip-commits@vger.kernel.org Subject: [tip: x86/urgent] x86/timer: Force PIT initialization when !X86_FEATURE_ARAT Cc: Jan Stancek , Thomas Gleixner , Ingo Molnar , Borislav Petkov , linux-kernel@vger.kernel.org MIME-Version: 1.0 Message-ID: <156792643484.24167.388160525662287317.tip-bot2@tip-bot2> X-Mailer: tip-git-log-daemon Robot-ID: Robot-Unsubscribe: Contact to get blacklisted from these emails Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 7bit X-Linutronix-Spam-Score: -1.0 X-Linutronix-Spam-Level: - X-Linutronix-Spam-Status: No , -1.0 points, 5.0 required, ALL_TRUSTED=-1,SHORTCIRCUIT=-0.0001 Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org The following commit has been merged into the x86/urgent branch of tip: Commit-ID: afa8b475c1aec185a8e106c48b3832e0b88bc2de Gitweb: https://git.kernel.org/tip/afa8b475c1aec185a8e106c48b3832e0b88bc2de Author: Jan Stancek AuthorDate: Sun, 08 Sep 2019 00:50:40 +02:00 Committer: Thomas Gleixner CommitterDate: Sun, 08 Sep 2019 09:01:15 +02:00 x86/timer: Force PIT initialization when !X86_FEATURE_ARAT KVM guests with commit c8c4076723da ("x86/timer: Skip PIT initialization on modern chipsets") applied to guest kernel have been observed to have unusually higher CPU usage with symptoms of increase in vm exits for HLT and MSW_WRITE (MSR_IA32_TSCDEADLINE). This is caused by older QEMUs lacking support for X86_FEATURE_ARAT. lapic clock retains CLOCK_EVT_FEAT_C3STOP and nohz stays inactive. There's no usable broadcast device either. Do the PIT initialization if guest CPU lacks X86_FEATURE_ARAT. On real hardware it shouldn't matter as ARAT and DEADLINE come together. Fixes: c8c4076723da ("x86/timer: Skip PIT initialization on modern chipsets") Signed-off-by: Jan Stancek Signed-off-by: Thomas Gleixner --- arch/x86/kernel/apic/apic.c | 4 ++++ 1 file changed, 4 insertions(+) diff --git a/arch/x86/kernel/apic/apic.c b/arch/x86/kernel/apic/apic.c index dba2828..f91b3ff 100644 --- a/arch/x86/kernel/apic/apic.c +++ b/arch/x86/kernel/apic/apic.c @@ -834,6 +834,10 @@ bool __init apic_needs_pit(void) if (!boot_cpu_has(X86_FEATURE_APIC)) return true; + /* Virt guests may lack ARAT, but still have DEADLINE */ + if (!boot_cpu_has(X86_FEATURE_ARAT)) + return true; + /* Deadline timer is based on TSC so no further PIT action required */ if (boot_cpu_has(X86_FEATURE_TSC_DEADLINE_TIMER)) return false;