linux-kernel - Re: [PATCH RFC 0/6] x86/kvm/hyperv: stable clocksorce for L2 guests when running nested KVM on Hyper-V

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Date:   Fri, 1 Dec 2017 17:11:24 +0100
From:   Paolo Bonzini <pbonzini@...hat.com>
To:     Vitaly Kuznetsov <vkuznets@...hat.com>, kvm@...r.kernel.org,
        x86@...nel.org
Cc:     Radim Krčmář <rkrcmar@...hat.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>,
        "H. Peter Anvin" <hpa@...or.com>,
        "K. Y. Srinivasan" <kys@...rosoft.com>,
        Haiyang Zhang <haiyangz@...rosoft.com>,
        Stephen Hemminger <sthemmin@...rosoft.com>,
        Andy Lutomirski <luto@...nel.org>,
        linux-kernel@...r.kernel.org, devel@...uxdriverproject.org
Subject: Re: [PATCH RFC 0/6] x86/kvm/hyperv: stable clocksorce for L2 guests
 when running nested KVM on Hyper-V

On 01/12/2017 14:13, Vitaly Kuznetsov wrote:
> Currently, KVM passes PVCLOCK_TSC_STABLE_BIT to its guests when running in
> so called 'masterclock' mode and this is only possible when the clocksource
> on the host is TSC. When running nested on Hyper-V we're using a different
> clocksource in L1 (Hyper-V TSC Page) which can actually be used for
> masterclock. This series brings the required support.
> 
> Making KVM work with TSC page clocksource is relatively easy, it is done in
> PATCH 5 of the series. All the rest is required to support L1 migration
> when TSC frequency changes, we use a special feature from Hyper-V to do
> the job.

This looks great.  If the Hyper-V folks can provide a topic branch with
patches 1-4 in it, we can merge it.

Thanks,

Paolo