linux-kernel - Re: [PATCH 3/4] KVM: x86: introduce get_kvmclock

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Message-ID: <8db8781a-a6d7-7e70-f8ef-221078a34770@redhat.com>
Date:   Mon, 5 Sep 2016 15:59:27 +0200
From:   Paolo Bonzini <pbonzini@...hat.com>
To:     Roman Kagan <rkagan@...tuozzo.com>, linux-kernel@...r.kernel.org,
        kvm@...r.kernel.org, peterhornyack@...gle.com, rkrcmar@...hat.com,
        den@...nvz.org
Subject: Re: [PATCH 3/4] KVM: x86: introduce get_kvmclock_ns



On 02/09/2016 17:24, Roman Kagan wrote:
> On Thu, Sep 01, 2016 at 05:26:14PM +0200, Paolo Bonzini wrote:
>> Introduce a function that reads the exact nanoseconds value that is
>> provided to the guest in kvmclock.  This crystallizes the notion of
>> kvmclock as a thin veneer over a stable TSC, that the guest will
>> (hopefully) convert with NTP.  In other words, kvmclock is *not* a
>> paravirtualized host-to-guest NTP.
> 
> It might also be worth documenting this approach in a comment somewhere
> around pvclock_gtod_notify / update_pvclock_gtod or friends.  And, if
> those could be simplified due to this change, it would be great, too.

Yes, Radim or I are going to look at it next...

Paolo