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From: John Stultz <john.stultz@linaro.org>
To: Denis Plotnikov <dplotnikov@virtuozzo.com>
Cc: Paolo Bonzini <pbonzini@redhat.com>,
	Radim Krcmar <rkrcmar@redhat.com>, kvm list <kvm@vger.kernel.org>,
	Thomas Gleixner <tglx@linutronix.de>,
	Ingo Molnar <mingo@redhat.com>, "H. Peter Anvin" <hpa@zytor.com>,
	lkml <linux-kernel@vger.kernel.org>,
	"x86@kernel.org" <x86@kernel.org>,
	rkagan@virtuozzo.com, den@virtuozzo.com,
	Marcelo Tosatti <mtosatti@redhat.com>
Subject: Re: [PATCH v4 00/10] make L2's kvm-clock stable, get rid of pvclock_gtod_copy in KVM
Date: Tue, 22 Aug 2017 12:50:06 -0700	[thread overview]
Message-ID: <CALAqxLWGf6BAdji=rqKPnyvFzzUQscA5rXU8SY4RcWXymyVL1Q@mail.gmail.com> (raw)
In-Reply-To: <f93105c1-0d6f-f9d4-fc43-31efae1c9aeb@virtuozzo.com>

On Mon, Aug 21, 2017 at 1:40 AM, Denis Plotnikov
<dplotnikov@virtuozzo.com> wrote:
> ping!
>

I still don't feel my questions have been well answered. Its really
not clear to me why, in order to allow the level-2 guest to use a vdso
that the answer is to export more data through the entire stack rather
then to make the kvmclock to be usable from the vsyscall.

So far for a problem statement, all I've got is:
"However, when using nested virtualization you have

        L0: bare-metal hypervisor (uses TSC)
        L1: nested hypervisor (uses kvmclock, can use vsyscall)
        L2: nested guest

and L2 cannot use vsyscall because it is not using the TSC."

Which is a start but doesn't really make it clear why the proposed
solution is best/necessary.

thanks
-john

  reply	other threads:[~2017-08-22 19:50 UTC|newest]

Thread overview: 27+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2017-08-02 14:38 [PATCH v4 00/10] make L2's kvm-clock stable, get rid of pvclock_gtod_copy in KVM Denis Plotnikov
2017-08-02 14:38 ` [PATCH v4 01/10] timekeeper: introduce extended clocksource reading callback Denis Plotnikov
2017-08-02 17:08   ` John Stultz
2017-08-02 17:21     ` Paolo Bonzini
2017-08-02 14:38 ` [PATCH v4 02/10] timekeeper: introduce boot field in system_time_snapshot Denis Plotnikov
2017-08-02 14:38 ` [PATCH v4 03/10] timekeeper: use the extended reading function on snapshot acquiring Denis Plotnikov
2017-08-02 14:38 ` [PATCH v4 04/10] tsc: implement the extended tsc reading function Denis Plotnikov
2017-08-02 14:38 ` [PATCH v4 05/10] KVM: x86: switch to masterclock update using timekeeper functionality Denis Plotnikov
2017-08-02 14:38 ` [PATCH v4 06/10] timekeeper: add clocksource change notifier Denis Plotnikov
2017-08-02 14:38 ` [PATCH v4 07/10] KVM: x86: remove not used pvclock_gtod_copy Denis Plotnikov
2017-08-02 23:21   ` Marcelo Tosatti
2017-08-03 12:35     ` Paolo Bonzini
2017-08-11 22:59       ` Marcelo Tosatti
2017-08-02 14:38 ` [PATCH v4 08/10] pvclock: add parameters to store stamp data in pvclock reading function Denis Plotnikov
2017-08-02 14:38 ` [PATCH v4 09/10] pvclock: add clocksource change notification on changing of tsc stable bit Denis Plotnikov
2017-08-02 23:36   ` Marcelo Tosatti
2017-08-02 14:38 ` [PATCH v4 10/10] kvmclock: implement the extended reading function Denis Plotnikov
2017-08-02 16:10 ` [PATCH v4 00/10] make L2's kvm-clock stable, get rid of pvclock_gtod_copy in KVM Paolo Bonzini
2017-08-02 16:49 ` John Stultz
2017-08-02 17:11   ` Paolo Bonzini
2017-08-21  8:40     ` Denis Plotnikov
2017-08-22 19:50       ` John Stultz [this message]
2017-08-22 21:00         ` Paolo Bonzini
2017-08-23 12:45           ` Thomas Gleixner
2017-08-23 16:02             ` Paolo Bonzini
2017-08-24  8:00               ` Paolo Bonzini
2017-08-28  7:28                 ` Denis Plotnikov

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