On 09/15/2014 03:33 PM, Radim Krčmář wrote:
> 2014-09-12 17:06-0400, Liang Chen:
>> Using kvm_mmu_flush_tlb as the other places to make sure vcpu
>>  stat is incremented
>>
>> Signed-off-by: Liang Chen <[email protected]>
>> ---
> Good catch.
>
>>  arch/x86/kvm/vmx.c | 2 +-
>>  1 file changed, 1 insertion(+), 1 deletion(-)
>>
>> diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c
>> index bfe11cf..439682e 100644
>> --- a/arch/x86/kvm/vmx.c
>> +++ b/arch/x86/kvm/vmx.c
>> @@ -1810,7 +1810,7 @@ static void vmx_vcpu_load(struct kvm_vcpu *vcpu, int 
>> cpu)
>>              struct desc_ptr *gdt = &__get_cpu_var(host_gdt);
>>              unsigned long sysenter_esp;
>>  
>> -            kvm_make_request(KVM_REQ_TLB_FLUSH, vcpu);
>> +            kvm_mmu_flush_tlb(vcpu);
>>              local_irq_disable();
>>              crash_disable_local_vmclear(cpu);
>>  
> And to hijack this thread ...
> I noticed three other deficits in stat.tlb_flush, patch below.
>
> Do you prefer the current behavior?

Yeah, you are right. I think the patch below gives a more thorough solution to
make sure the counter really shows the number of tlb flushes - not the time 
kvm_mmu_flush_tlb is called. Thanks!

> --- 8< ---
> KVM: x86: count actual tlb flushes
>
> - we count KVM_REQ_TLB_FLUSH requests, not actual flushes
>   (KVM can have multiple requests for one flush)
> - flushes from kvm_flush_remote_tlbs aren't counted
> - it's easy to make a direct request by mistake
>
> Solve these by postponing the counting to kvm_check_request().
>
> Signed-off-by: Radim Krčmář <[email protected]>
> ---
> (And what about a possible followup patch that replaces
>  kvm_mmu_flush_tlb() with kvm_make_request() again?
>  It would free the namespace a bit and we could call something
>  similarly named from vcpu_enter_guest() to do the job.)

That seems good. I can take the labor to make the followup patch ;)

Thanks,
Liang Chen

> diff --git a/arch/x86/kvm/mmu.c b/arch/x86/kvm/mmu.c
> index 9314678..b41fd97 100644
> --- a/arch/x86/kvm/mmu.c
> +++ b/arch/x86/kvm/mmu.c
> @@ -3452,7 +3452,6 @@ static void nonpaging_init_context(struct kvm_vcpu 
> *vcpu,
>  
>  void kvm_mmu_flush_tlb(struct kvm_vcpu *vcpu)
>  {
> -     ++vcpu->stat.tlb_flush;
>       kvm_make_request(KVM_REQ_TLB_FLUSH, vcpu);
>  }
>  EXPORT_SYMBOL_GPL(kvm_mmu_flush_tlb);
> diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
> index 916e895..0f0ad08 100644
> --- a/arch/x86/kvm/x86.c
> +++ b/arch/x86/kvm/x86.c
> @@ -6041,8 +6041,10 @@ static int vcpu_enter_guest(struct kvm_vcpu *vcpu)
>               }
>               if (kvm_check_request(KVM_REQ_MMU_SYNC, vcpu))
>                       kvm_mmu_sync_roots(vcpu);
> -             if (kvm_check_request(KVM_REQ_TLB_FLUSH, vcpu))
> +             if (kvm_check_request(KVM_REQ_TLB_FLUSH, vcpu)) {
> +                     ++vcpu->stat.tlb_flush;
>                       kvm_x86_ops->tlb_flush(vcpu);
> +             }
>               if (kvm_check_request(KVM_REQ_REPORT_TPR_ACCESS, vcpu)) {
>                       vcpu->run->exit_reason = KVM_EXIT_TPR_ACCESS;
>                       r = 0;

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