linux-kernel - Re: [patch 00/11] x86/vdso: Cleanups, simmplifications and CLOCK

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Message-ID: <alpine.DEB.2.21.1810031704480.23677@nanos.tec.linutronix.de>
Date:   Wed, 3 Oct 2018 17:10:08 +0200 (CEST)
From:   Thomas Gleixner <tglx@...utronix.de>
To:     Andy Lutomirski <luto@...capital.net>
cc:     Vitaly Kuznetsov <vkuznets@...hat.com>,
        Andy Lutomirski <luto@...nel.org>,
        Marcelo Tosatti <mtosatti@...hat.com>,
        Paolo Bonzini <pbonzini@...hat.com>,
        Radim Krcmar <rkrcmar@...hat.com>,
        Wanpeng Li <kernellwp@...il.com>,
        LKML <linux-kernel@...r.kernel.org>, X86 ML <x86@...nel.org>,
        Peter Zijlstra <peterz@...radead.org>,
        Matt Rickard <matt@...trans.com.au>,
        Stephen Boyd <sboyd@...nel.org>,
        John Stultz <john.stultz@...aro.org>,
        Florian Weimer <fweimer@...hat.com>,
        KY Srinivasan <kys@...rosoft.com>,
        devel@...uxdriverproject.org,
        Linux Virtualization <virtualization@...ts.linux-foundation.org>,
        Arnd Bergmann <arnd@...db.de>, Juergen Gross <jgross@...e.com>
Subject: Re: [patch 00/11] x86/vdso: Cleanups, simmplifications and CLOCK_TAI
 support

On Wed, 3 Oct 2018, Andy Lutomirski wrote:
> > On Oct 3, 2018, at 5:01 AM, Vitaly Kuznetsov <vkuznets@...hat.com> wrote:
> > Not all Hyper-V hosts support reenlightenment notifications (and, if I'm
> > not mistaken, you need to enable nesting for the VM to get the feature -
> > and most VMs don't have this) so I think we'll have to keep Hyper-V
> > vclock for the time being.
> > 
> But this does suggest that the correct way to pass a clock through to an
> L2 guest where L0 is HV is to make L1 use the “tsc” clock and L2 use
> kvmclock (or something newer and better).  This would require adding
> support for atomic frequency changes all the way through the timekeeping
> and arch code.
>
> John, tglx, would that be okay or crazy?

Not sure what you mean. I think I lost you somewhere on the way.

Thanks,

	tglx