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Re: [PATCH] KVM: Remove redundant smp_mb() in the kvm_mmu_commit_zap_page()

From Lan Tianyu <tianyu.lan@intel.com>
Newsgroups linux.kernel
Subject Re: [PATCH] KVM: Remove redundant smp_mb() in the kvm_mmu_commit_zap_page()
Date 2016-03-04 08:30 +0100
Message-ID <r8Sls-38B-11@gated-at.bofh.it> (permalink)
References <r8Nc6-7Fq-9@gated-at.bofh.it> <r8Sls-38B-13@gated-at.bofh.it>
Organization linux.* mail to news gateway

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On 2016年03月04日 15:21, Thomas Gleixner wrote:
> On Fri, 4 Mar 2016, Lan Tianyu wrote:
> 
>> The following kvm_flush_remote_tlbs() will call smp_mb() inside and so
>> remove smp_mb() here.
>>
>> Signed-off-by: Lan Tianyu <tianyu.lan@intel.com>
>> ---
>>  arch/x86/kvm/mmu.c | 6 ------
>>  1 file changed, 6 deletions(-)
>>
>> diff --git a/arch/x86/kvm/mmu.c b/arch/x86/kvm/mmu.c
>> index a54ecd9..6315416 100644
>> --- a/arch/x86/kvm/mmu.c
>> +++ b/arch/x86/kvm/mmu.c
>> @@ -2383,12 +2383,6 @@ static void kvm_mmu_commit_zap_page(struct kvm *kvm,
>>  		return;
>>  
>>  	/*
>> -	 * wmb: make sure everyone sees our modifications to the page tables
>> -	 * rmb: make sure we see changes to vcpu->mode
> 
> You want to leave the comment explaining the memory barriers and tell that
> kvm_flush_remote_tlbs() contains the smp_mb().

That sounds more reasonable. Will update. Thanks.

> 
>> -	 */
>> -	smp_mb();
>> -
>> -	/*
>>  	 * Wait for all vcpus to exit guest mode and/or lockless shadow
>>  	 * page table walks.
>>  	 */
>> -- 
>> 1.8.4.rc0.1.g8f6a3e5.dirty
>>
>>


-- 
Best regards
Tianyu Lan

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Thread

[PATCH] KVM: Remove redundant smp_mb() in the kvm_mmu_commit_zap_page() Lan Tianyu <tianyu.lan@intel.com> - 2016-03-04 03:00 +0100
  Re: [PATCH] KVM: Remove redundant smp_mb() in the kvm_mmu_commit_zap_page() Lan Tianyu <tianyu.lan@intel.com> - 2016-03-04 08:30 +0100
    Re: [PATCH] KVM: Remove redundant smp_mb() in the  kvm_mmu_commit_zap_page() Paolo Bonzini <pbonzini@redhat.com> - 2016-03-04 09:50 +0100
      Re: [PATCH] KVM: Remove redundant smp_mb() in the kvm_mmu_commit_zap_page() Lan Tianyu <tianyu.lan@intel.com> - 2016-03-08 10:00 +0100
        Re: [PATCH] KVM: Remove redundant smp_mb() in the  kvm_mmu_commit_zap_page() Paolo Bonzini <pbonzini@redhat.com> - 2016-03-08 16:30 +0100
          Re: [PATCH] KVM: Remove redundant smp_mb() in the kvm_mmu_commit_zap_page() Lan Tianyu <tianyu.lan@intel.com> - 2016-03-09 08:40 +0100
            Re: [PATCH] KVM: Remove redundant smp_mb() in the  kvm_mmu_commit_zap_page() Paolo Bonzini <pbonzini@redhat.com> - 2016-03-10 18:10 +0100
              Re: [PATCH] KVM: Remove redundant smp_mb() in the  kvm_mmu_commit_zap_page() Xiao Guangrong <guangrong.xiao@linux.intel.com> - 2016-03-10 19:20 +0100
          Re: [PATCH] KVM: Remove redundant smp_mb() in the  kvm_mmu_commit_zap_page() Xiao Guangrong <guangrong.xiao@linux.intel.com> - 2016-03-10 15:50 +0100
            Re: [PATCH] KVM: Remove redundant smp_mb() in the  kvm_mmu_commit_zap_page() Paolo Bonzini <pbonzini@redhat.com> - 2016-03-10 16:30 +0100
              Re: [PATCH] KVM: Remove redundant smp_mb() in the  kvm_mmu_commit_zap_page() Paolo Bonzini <pbonzini@redhat.com> - 2016-03-10 16:40 +0100
                Re: [PATCH] KVM: Remove redundant smp_mb() in the  kvm_mmu_commit_zap_page() Xiao Guangrong <guangrong.xiao@linux.intel.com> - 2016-03-10 16:50 +0100
                Re: [PATCH] KVM: Remove redundant smp_mb() in the  kvm_mmu_commit_zap_page() Paolo Bonzini <pbonzini@redhat.com> - 2016-03-10 17:10 +0100
                Re: [PATCH] KVM: Remove redundant smp_mb() in the  kvm_mmu_commit_zap_page() Xiao Guangrong <guangrong.xiao@linux.intel.com> - 2016-03-10 19:20 +0100
              Re: [PATCH] KVM: Remove redundant smp_mb() in the kvm_mmu_commit_zap_page() Lan Tianyu <tianyu.lan@intel.com> - 2016-03-11 02:40 +0100
  Re: [PATCH] KVM: Remove redundant smp_mb() in the  kvm_mmu_commit_zap_page() Thomas Gleixner <tglx@linutronix.de> - 2016-03-04 08:30 +0100
  Re: [PATCH] KVM: Remove redundant smp_mb() in the  kvm_mmu_commit_zap_page() Paolo Bonzini <pbonzini@redhat.com> - 2016-03-04 09:10 +0100
    Re: [PATCH] KVM: Remove redundant smp_mb() in the  kvm_mmu_commit_zap_page() Xiao Guangrong <guangrong.xiao@linux.intel.com> - 2016-03-04 14:50 +0100

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