From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751414AbdB0MvP (ORCPT ); Mon, 27 Feb 2017 07:51:15 -0500 Received: from mx1.redhat.com ([209.132.183.28]:40220 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751030AbdB0MvL (ORCPT ); Mon, 27 Feb 2017 07:51:11 -0500 Subject: Re: tip.today - scheduler bam boom crash (cpu hotplug) To: Peter Zijlstra , Wanpeng Li References: <1484811069.17751.14.camel@gmx.de> <20170119101924.GJ6485@twins.programming.kicks-ass.net> <20170119133633.GB6536@twins.programming.kicks-ass.net> <20170227124349.GU6515@twins.programming.kicks-ass.net> Cc: Mike Galbraith , LKML , Ingo Molnar , Thomas Gleixner , Borislav Petkov From: Paolo Bonzini Message-ID: <3e7c34e2-757b-19e9-f7e5-9bfaadd79e5d@redhat.com> Date: Mon, 27 Feb 2017 13:50:29 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:45.0) Gecko/20100101 Thunderbird/45.7.0 MIME-Version: 1.0 In-Reply-To: <20170227124349.GU6515@twins.programming.kicks-ass.net> Content-Type: text/plain; charset=windows-1252 Content-Transfer-Encoding: 7bit X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.30]); Mon, 27 Feb 2017 12:50:34 +0000 (UTC) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 27/02/2017 13:43, Peter Zijlstra wrote: > On Mon, Feb 27, 2017 at 08:30:11PM +0800, Wanpeng Li wrote: > >>> diff --git a/arch/x86/kernel/kvmclock.c b/arch/x86/kernel/kvmclock.c >>> index 2a5cafd..542710b 100644 >>> --- a/arch/x86/kernel/kvmclock.c >>> +++ b/arch/x86/kernel/kvmclock.c >>> @@ -107,12 +107,12 @@ static inline void kvm_sched_clock_init(bool stable) >>> { >>> if (!stable) { >>> pv_time_ops.sched_clock = kvm_clock_read; >>> + clear_sched_clock_stable(); >>> return; >>> } >>> >>> kvm_sched_clock_offset = kvm_clock_read(); >>> pv_time_ops.sched_clock = kvm_sched_clock_read; >>> - set_sched_clock_stable(); >> >> This results in sched clock always unstable for kvm guest since there >> is no invariant tsc cpuid bit exposed for kvm guest currently. > > What the heck is KVM_FEATURE_CLOCKSOURCE_STABLE_BIT / > PVCLOCK_TSC_STABLE_BIT about then? It checks that all the bugs in the host have been ironed out, and that the host itself supports invtsc. Paolo