linux-kernel - Re: [PATCH V4 14/15] KVM/VMX: Change hv flush logic when ept tables are mismatched.

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Message-ID: <829117f9-350e-239b-f9f5-da5b7f33a5dd@redhat.com>
Date:   Mon, 15 Oct 2018 13:15:45 +0200
From:   Paolo Bonzini <pbonzini@...hat.com>
To:     lantianyu1986@...il.com
Cc:     Lan Tianyu <Tianyu.Lan@...rosoft.com>, rkrcmar@...hat.com,
        tglx@...utronix.de, mingo@...hat.com, hpa@...or.com,
        x86@...nel.org, kvm@...r.kernel.org, linux-kernel@...r.kernel.org,
        michael.h.kelley@...rosoft.com, kys@...rosoft.com,
        vkuznets@...hat.com
Subject: Re: [PATCH V4 14/15] KVM/VMX: Change hv flush logic when ept tables
 are mismatched.

On 13/10/2018 16:54, lantianyu1986@...il.com wrote:
> From: Lan Tianyu <Tianyu.Lan@...rosoft.com>
> 
> If ept table pointers are mismatched, flushing tlb for each vcpus via
> hv flush interface still helps to reduce vmexits which are triggered
> by IPI and INEPT emulation.
> 
> Signed-off-by: Lan Tianyu <Tianyu.Lan@...rosoft.com>
> ---
>  arch/x86/kvm/vmx.c | 15 ++++++++-------
>  1 file changed, 8 insertions(+), 7 deletions(-)
> 
> diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c
> index 6f44d3a63434..8ff13f3aed11 100644
> --- a/arch/x86/kvm/vmx.c
> +++ b/arch/x86/kvm/vmx.c
> @@ -1571,7 +1571,8 @@ static void check_ept_pointer_match(struct kvm *kvm)
>  
>  static int vmx_hv_remote_flush_tlb(struct kvm *kvm)
>  {
> -	int ret;
> +	struct kvm_vcpu *vcpu;
> +	int ret = -ENOTSUPP, i;
>  
>  	spin_lock(&to_kvm_vmx(kvm)->ept_pointer_lock);
>  
> @@ -1579,14 +1580,14 @@ static int vmx_hv_remote_flush_tlb(struct kvm *kvm)
>  		check_ept_pointer_match(kvm);
>  
>  	if (to_kvm_vmx(kvm)->ept_pointers_match != EPT_POINTERS_MATCH) {
> -		ret = -ENOTSUPP;
> -		goto out;
> +		kvm_for_each_vcpu(i, vcpu, kvm)
> +			ret |= hyperv_flush_guest_mapping(
> +				to_vmx(kvm_get_vcpu(kvm, i))->ept_pointer);
> +	} else {
> +		ret = hyperv_flush_guest_mapping(
> +				to_vmx(kvm_get_vcpu(kvm, 0))->ept_pointer);
>  	}
>  
> -	ret = hyperv_flush_guest_mapping(
> -			to_vmx(kvm_get_vcpu(kvm, 0))->ept_pointer);
> -
> -out:
>  	spin_unlock(&to_kvm_vmx(kvm)->ept_pointer_lock);
>  	return ret;
>  }
> 

I think this is an independent change that can be applied separately?

Thanks,

Paolo