From mboxrd@z Thu Jan  1 00:00:00 1970
Return-Path: <linux-kernel-owner@vger.kernel.org>
Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand
        id S1751596AbdB0Mob (ORCPT <rfc822;w@1wt.eu>);
        Mon, 27 Feb 2017 07:44:31 -0500
Received: from merlin.infradead.org ([205.233.59.134]:44440 "EHLO
        merlin.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org
        with ESMTP id S1751407AbdB0MoD (ORCPT
        <rfc822;linux-kernel@vger.kernel.org>);
        Mon, 27 Feb 2017 07:44:03 -0500
Date: Mon, 27 Feb 2017 13:43:49 +0100
From: Peter Zijlstra <peterz@infradead.org>
To: Wanpeng Li <kernellwp@gmail.com>
Cc: Mike Galbraith <efault@gmx.de>, LKML <linux-kernel@vger.kernel.org>,
        Ingo Molnar <mingo@elte.hu>, Thomas Gleixner <tglx@linutronix.de>,
        Borislav Petkov <bp@alien8.de>, Paolo Bonzini <pbonzini@redhat.com>
Subject: Re: tip.today - scheduler bam boom crash (cpu hotplug)
Message-ID: <20170227124349.GU6515@twins.programming.kicks-ass.net>
References: <1484811069.17751.14.camel@gmx.de>
 <20170119101924.GJ6485@twins.programming.kicks-ass.net>
 <20170119133633.GB6536@twins.programming.kicks-ass.net>
 <CANRm+CwH7mUkHGshKLJH5R28LUVHxfHiqfYP+CQYyhMUrnWo0g@mail.gmail.com>
MIME-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Content-Disposition: inline
In-Reply-To: <CANRm+CwH7mUkHGshKLJH5R28LUVHxfHiqfYP+CQYyhMUrnWo0g@mail.gmail.com>
User-Agent: Mutt/1.5.23.1 (2014-03-12)
Sender: linux-kernel-owner@vger.kernel.org
List-ID: <linux-kernel.vger.kernel.org>
X-Mailing-List: linux-kernel@vger.kernel.org

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?

> How about something like below(untested):

I have no clue what that tries to do.