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Re: [PATCH 2/2] x86, kvm: use kvmclock to compute TSC deadline value

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On Fri, Sep 9, 2016 at 9:38 AM, Paolo Bonzini <pbonzini@redhat.com> wrote:
>
> On 09/09/2016 00:13, David Matlack wrote:
>> Hi Paolo,
>>
>> On Tue, Sep 6, 2016 at 3:29 PM, Paolo Bonzini <pbonzini@redhat.com> wrote:
>>> Bad things happen if a guest using the TSC deadline timer is migrated.
>>> The guest doesn't re-calibrate the TSC after migration, and the
>>> TSC frequency can and will change unless your processor supports TSC
>>> scaling (on Intel this is only Skylake) or your data center is perfectly
>>> homogeneous.
>>
>> Sorry, I forgot to follow up on our discussion in v1. One thing we
>> discussed there was using the APIC Timer to workaround a changing TSC
>> rate. You pointed out KVM's TSC deadline timer got a nice performance
>> boost recently, which makes it preferable. Does it makes sense to
>> apply the same optimization (using the VMX preemption timer) to the
>> APIC Timer, instead of creating a new dependency on kvmclock?
>
> Hi, yes it does.  If we go that way kvmclock.c should be patched to
> blacklist the TSC deadline timer.  However, I won't have time to work on
> it anytime soon, so _if I get reviews_ I'll take this patch first.

Got it, thanks for the context.

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[PATCH v2 0/2] if running under KVM, use kvmclock to compute TSC deadline value Paolo Bonzini <pbonzini@redhat.com> - 2016-09-07 00:40 +0200
  [PATCH 2/2] x86, kvm: use kvmclock to compute TSC deadline value Paolo Bonzini <pbonzini@redhat.com> - 2016-09-07 00:40 +0200
    Re: [PATCH 2/2] x86, kvm: use kvmclock to compute TSC deadline value David Matlack <dmatlack@google.com> - 2016-09-09 00:20 +0200
      Re: [PATCH 2/2] x86, kvm: use kvmclock to compute TSC deadline value Paolo Bonzini <pbonzini@redhat.com> - 2016-09-09 18:40 +0200
        Re: [PATCH 2/2] x86, kvm: use kvmclock to compute TSC deadline value David Matlack <dmatlack@google.com> - 2016-09-09 22:10 +0200
    Re: [PATCH 2/2] x86, kvm: use kvmclock to compute TSC deadline value Radim Krčmář <rkrcmar@redhat.com> - 2016-09-15 17:10 +0200
      Re: [PATCH 2/2] x86, kvm: use kvmclock to compute TSC deadline value Paolo Bonzini <pbonzini@redhat.com> - 2016-09-15 18:10 +0200
        Re: [PATCH 2/2] x86, kvm: use kvmclock to compute TSC deadline value Radim Krčmář <rkrcmar@redhat.com> - 2016-09-15 22:10 +0200
          Re: [PATCH 2/2] x86, kvm: use kvmclock to compute TSC deadline value Paolo Bonzini <pbonzini@redhat.com> - 2016-09-15 23:10 +0200
            Re: [PATCH 2/2] x86, kvm: use kvmclock to compute TSC deadline value Radim Krčmář <rkrcmar@redhat.com> - 2016-09-16 17:10 +0200
              Re: [PATCH 2/2] x86, kvm: use kvmclock to compute TSC deadline value Paolo Bonzini <pbonzini@redhat.com> - 2016-09-16 17:10 +0200
                Re: [PATCH 2/2] x86, kvm: use kvmclock to compute TSC deadline value Radim Krčmář <rkrcmar@redhat.com> - 2016-09-16 17:30 +0200
  [PATCH 1/2] x86: paravirt: add local_apic_timer_interrupt to pv_ops Paolo Bonzini <pbonzini@redhat.com> - 2016-09-07 00:40 +0200
    Re: [PATCH 1/2] x86: paravirt: add local_apic_timer_interrupt to  pv_ops kbuild test robot <lkp@intel.com> - 2016-09-07 08:30 +0200
    Re: [PATCH 1/2] x86: paravirt: add local_apic_timer_interrupt to  pv_ops kbuild test robot <lkp@intel.com> - 2016-09-07 08:40 +0200

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