From: Marcelo Tosatti <mtosatti@redhat.com>
To: Radim Krcmar <rkrcmar@redhat.com>,
Miroslav Lichvar <mlichvar@redhat.com>
Cc: kvm@vger.kernel.org, linux-kernel@vger.kernel.org,
Paolo Bonzini <pbonzini@redhat.com>,
Richard Cochran <richardcochran@gmail.com>,
Miroslav Lichvar <mlichvar@redhat.com>
Subject: Re: [patch 3/3] PTP: add kvm PTP driver
Date: Mon, 16 Jan 2017 17:36:55 -0200 [thread overview]
Message-ID: <20170116193655.GA7649@amt.cnet> (raw)
In-Reply-To: <20170116180147.GD31452@potion>
On Mon, Jan 16, 2017 at 07:01:48PM +0100, Radim Krcmar wrote:
> > Sorry the clock difference is 10ns now. So the guest clock is off by _10 ns_
> > of the host clock.
>
> That is pretty good.
Yes.
> > You are suggesting to use getcrosststamp instead, to drop the (rdtsc() -
> > guest_tsc) part ?
>
> Yes, it results in simpler code, doesn't create dependency on the
> dreaded kvmclock, and is the best we can currently do wrt. precision.
Sorry, unless i am misunderstanding how this works, it'll get the guest clock
2us behind, which is something not wanted.
Miroslav, if ->gettime64 returns the host realtime at 2us in the past,
this means Chrony will sync the guest clock to
host realtime - 2us
Is that correct?
next prev parent reply other threads:[~2017-01-16 19:37 UTC|newest]
Thread overview: 54+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-01-13 12:01 [patch 0/3] KVM virtual " Marcelo Tosatti
2017-01-13 12:01 ` [patch 1/3] KVM: x86: provide realtime host clock via vsyscall notifiers Marcelo Tosatti
2017-01-13 15:18 ` Radim Krcmar
2017-01-13 15:34 ` Marcelo Tosatti
2017-01-13 16:28 ` Radim Krcmar
2017-01-13 17:51 ` Marcelo Tosatti
2017-01-16 15:40 ` Radim Krcmar
2017-01-13 15:41 ` Konrad Rzeszutek Wilk
2017-01-13 15:46 ` Marcelo Tosatti
2017-01-13 12:01 ` [patch 2/3] KVM: x86: add KVM_HC_CLOCK_OFFSET hypercall Marcelo Tosatti
2017-01-13 15:31 ` Radim Krcmar
2017-01-13 15:43 ` Marcelo Tosatti
2017-01-13 17:07 ` Radim Krcmar
2017-01-13 17:57 ` Marcelo Tosatti
2017-01-13 12:01 ` [patch 3/3] PTP: add kvm PTP driver Marcelo Tosatti
2017-01-13 15:56 ` Radim Krcmar
2017-01-13 17:40 ` Marcelo Tosatti
2017-01-16 16:26 ` Radim Krcmar
2017-01-16 16:54 ` Radim Krcmar
2017-01-16 17:08 ` Marcelo Tosatti
2017-01-16 17:27 ` Radim Krcmar
2017-01-16 17:39 ` Marcelo Tosatti
2017-01-16 18:01 ` Radim Krcmar
2017-01-16 19:36 ` Marcelo Tosatti [this message]
2017-01-16 19:47 ` Marcelo Tosatti
2017-01-16 20:01 ` Marcelo Tosatti
2017-01-17 8:03 ` Miroslav Lichvar
2017-01-17 11:30 ` Marcelo Tosatti
2017-01-17 15:36 ` Radim Krcmar
2017-01-18 12:17 ` Marcelo Tosatti
2017-01-18 12:24 ` Marcelo Tosatti
2017-01-18 12:46 ` Paolo Bonzini
2017-01-18 13:36 ` Miroslav Lichvar
2017-01-18 14:02 ` Paolo Bonzini
2017-01-18 14:50 ` Marcelo Tosatti
2017-01-18 15:35 ` Radim Krcmar
2017-01-18 15:45 ` Paolo Bonzini
2017-01-18 15:57 ` Marcelo Tosatti
2017-01-18 14:24 ` Marcelo Tosatti
2017-01-18 15:54 ` Miroslav Lichvar
2017-01-18 16:07 ` Paolo Bonzini
2017-01-18 16:14 ` Radim Krcmar
2017-01-18 14:37 ` Marcelo Tosatti
2017-01-18 14:53 ` Marcelo Tosatti
2017-01-18 15:20 ` Radim Krcmar
2017-01-18 15:28 ` Marcelo Tosatti
2017-01-20 14:18 ` Radim Krcmar
2017-01-18 15:59 ` Radim Krcmar
2017-01-16 17:04 ` Marcelo Tosatti
2017-01-16 17:46 ` Radim Krcmar
2017-01-16 19:33 ` Marcelo Tosatti
2017-01-14 15:26 ` Richard Cochran
2017-01-16 15:48 ` Radim Krcmar
2017-01-13 18:45 [patch 0/3] KVM virtual PTP driver (v2) Marcelo Tosatti
2017-01-13 18:46 ` [patch 3/3] PTP: add kvm PTP driver Marcelo Tosatti
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