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Re: [PATCH 1/2] KVM: x86: fix ordering of cr0 initialization code in vmx_cpu_reset

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>>> On 2/8/2016 at 08:09 AM, Paolo Bonzini <pbonzini@redhat.com> wrote: 

> 
> On 03/02/2016 23:51, Bruce Rogers wrote:
>> 
>> diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c
>> index e2951b6..21507b4 100644
>> --- a/arch/x86/kvm/vmx.c
>> +++ b/arch/x86/kvm/vmx.c
>> @@ -4993,8 +4993,8 @@ static void vmx_vcpu_reset(struct kvm_vcpu *vcpu, bool 
> init_event)
>>  		vmcs_write16(VIRTUAL_PROCESSOR_ID, vmx->vpid);
>>  
>>  	cr0 = X86_CR0_NW | X86_CR0_CD | X86_CR0_ET;
>> -	vmx_set_cr0(vcpu, cr0); /* enter rmode */
>>  	vmx->vcpu.arch.cr0 = cr0;
>> +	vmx_set_cr0(vcpu, cr0); /* enter rmode */
> 
> Your comment that the assignment is redundant is correct, but I am
> afraid that this fix is also wrong.  In particular, it would not cause
> exit_lmode and enter_rmode to be called.
> 
> You are not describing which call to kvm_mmu_reset_context was messed
> up, so I'm not sure how your patch is fixing things.

This is in the context of AP sending INIT to BSP with unrestricted_guest=N.

So the call sequence where I see the issue is: kvm_apic_accept_events() ->
kvm_vcpu_reset() -> vmx_vcpu_reset() -> vmx_set_cr0() -> enter_rmode() ->
kvm_mmu_reset_context().

enter_rmode is called in the case I am testing.

Bruce

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[PATCH 1/2] KVM: x86: fix ordering of cr0 initialization code in vmx_cpu_reset Bruce Rogers <brogers@suse.com> - 2016-02-04 00:20 +0100
  [PATCH 2/2] KVM: x86: allow BSP to handle INIT IPIs like APs do Bruce Rogers <brogers@suse.com> - 2016-02-04 00:20 +0100
    Re: [PATCH 2/2] KVM: x86: allow BSP to handle INIT IPIs like APs do Paolo Bonzini <pbonzini@redhat.com> - 2016-02-08 16:20 +0100
      Re: [PATCH 2/2] KVM: x86: allow BSP to handle INIT IPIs like APs do Jan Kiszka <jan.kiszka@web.de> - 2016-02-08 16:30 +0100
        Re: [PATCH 2/2] KVM: x86: allow BSP to handle INIT IPIs like  APs do "Bruce Rogers" <brogers@suse.com> - 2016-02-08 17:40 +0100
          Re: [PATCH 2/2] KVM: x86: allow BSP to handle INIT IPIs like APs do Paolo Bonzini <pbonzini@redhat.com> - 2016-02-08 17:50 +0100
            Re: [PATCH 2/2] KVM: x86: allow BSP to handle INIT IPIs like  APs do "Bruce Rogers" <brogers@suse.com> - 2016-02-08 18:30 +0100
              Re: [PATCH 2/2] KVM: x86: allow BSP to handle INIT IPIs like APs do Paolo Bonzini <pbonzini@redhat.com> - 2016-02-08 18:50 +0100
            Re: [PATCH 2/2] KVM: x86: allow BSP to handle INIT IPIs like  APs do "Bruce Rogers" <brogers@suse.com> - 2016-02-08 18:40 +0100
              Re: [PATCH 2/2] KVM: x86: allow BSP to handle INIT IPIs like APs do Jan Kiszka <jan.kiszka@web.de> - 2016-02-08 19:00 +0100
  Re: [PATCH 1/2] KVM: x86: fix ordering of cr0 initialization code in vmx_cpu_reset Nadav Amit <nadav.amit@gmail.com> - 2016-02-04 00:20 +0100
    Re: [PATCH 1/2] KVM: x86: fix ordering of cr0 initialization  code in vmx_cpu_reset "Bruce Rogers" <brogers@suse.com> - 2016-02-04 00:40 +0100
  Re: [PATCH 1/2] KVM: x86: fix ordering of cr0 initialization code in  vmx_cpu_reset Paolo Bonzini <pbonzini@redhat.com> - 2016-02-08 16:10 +0100
    Re: [PATCH 1/2] KVM: x86: fix ordering of cr0 initialization  code in vmx_cpu_reset "Bruce Rogers" <brogers@suse.com> - 2016-02-08 17:30 +0100
      Re: [PATCH 1/2] KVM: x86: fix ordering of cr0 initialization code in  vmx_cpu_reset Paolo Bonzini <pbonzini@redhat.com> - 2016-02-08 17:50 +0100

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