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Re: [PATCH] KVM: VMX: switch to hrtimer for TSC deadline timer when L2 guest is running

From Paolo Bonzini <pbonzini@redhat.com>
Newsgroups linux.kernel
Subject Re: [PATCH] KVM: VMX: switch to hrtimer for TSC deadline timer when L2 guest is running
Date 2016-07-06 08:10 +0200
Message-ID <rROc1-5vh-7@gated-at.bofh.it> (permalink)
References <rRNpD-4Ya-9@gated-at.bofh.it> <rRNJ0-563-13@gated-at.bofh.it>
Organization linux.* mail to news gateway

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On 06/07/2016 07:37, Wanpeng Li wrote:
> Cc Jan,
> 2016-07-06 13:10 GMT+08:00 Haozhong Zhang <haozhong.zhang@intel.com>:
>> A different VMCS is loaded when L2 guest is running, so it's incorrect
>> to use the VMX preemption timer for L1 TSC deadline timer. This patch
>> switches to hrtimer for L1 TSC deadline timer when entering L2 guest,
>> and switches back to VMX preemption timer when nested VMEXIT from L2 to
>> L1.
> 
> Nested preemption timer is emulated by hrtimer, so it doesn't
> influence vmcs02, why this is needed?

I agree (and nested APIC timer is emulated by L1).  Because the L1 APIC
timer is set in the preemption timer before vmentry, this should not be
necessary.

Paolo

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Thread

[PATCH] KVM: VMX: switch to hrtimer for TSC deadline timer when L2 guest is running Haozhong Zhang <haozhong.zhang@intel.com> - 2016-07-06 07:20 +0200
  Re: [PATCH] KVM: VMX: switch to hrtimer for TSC deadline timer when  L2 guest is running Wanpeng Li <kernellwp@gmail.com> - 2016-07-06 07:40 +0200
    Re: [PATCH] KVM: VMX: switch to hrtimer for TSC deadline timer when  L2 guest is running Paolo Bonzini <pbonzini@redhat.com> - 2016-07-06 08:10 +0200
    Re: [PATCH] KVM: VMX: switch to hrtimer for TSC deadline timer when  L2 guest is running Haozhong Zhang <haozhong.zhang@intel.com> - 2016-07-06 08:10 +0200
      Re: [PATCH] KVM: VMX: switch to hrtimer for TSC deadline timer when  L2 guest is running Paolo Bonzini <pbonzini@redhat.com> - 2016-07-06 09:50 +0200
        Re: [PATCH] KVM: VMX: switch to hrtimer for TSC deadline timer when  L2 guest is running Haozhong Zhang <haozhong.zhang@intel.com> - 2016-07-06 10:10 +0200
          Re: [PATCH] KVM: VMX: switch to hrtimer for TSC deadline timer when  L2 guest is running Haozhong Zhang <haozhong.zhang@intel.com> - 2016-07-06 10:10 +0200
            Re: [PATCH] KVM: VMX: switch to hrtimer for TSC deadline timer when  L2 guest is running Paolo Bonzini <pbonzini@redhat.com> - 2016-07-06 10:20 +0200
              Re: [PATCH] KVM: VMX: switch to hrtimer for TSC deadline timer when  L2 guest is running Haozhong Zhang <haozhong.zhang@intel.com> - 2016-07-06 10:30 +0200

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