linux-kernel - Re: [PATCH 07/14] KVM: x86: hyper-v: Introduce kvm_hv_nested_transtion_tlb

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Message-ID: <66b737135fd8a12f8b79ef22a9b1cef8f9c56496.camel@redhat.com>
Date:   Tue, 07 Nov 2023 20:21:27 +0200
From:   Maxim Levitsky <mlevitsk@...hat.com>
To:     Vitaly Kuznetsov <vkuznets@...hat.com>, kvm@...r.kernel.org,
        Paolo Bonzini <pbonzini@...hat.com>,
        Sean Christopherson <seanjc@...gle.com>
Cc:     linux-kernel@...r.kernel.org
Subject: Re: [PATCH 07/14] KVM: x86: hyper-v: Introduce
 kvm_hv_nested_transtion_tlb_flush() helper

On Wed, 2023-10-25 at 17:23 +0200, Vitaly Kuznetsov wrote:
> As a preparation to making Hyper-V emulation optional, introduce a helper
> to handle pending KVM_REQ_HV_TLB_FLUSH requests.
> 
> No functional change intended.
> 
> Signed-off-by: Vitaly Kuznetsov <vkuznets@...hat.com>
> ---
>  arch/x86/kvm/hyperv.h     | 12 ++++++++++++
>  arch/x86/kvm/svm/nested.c | 10 ++--------
>  arch/x86/kvm/vmx/nested.c | 10 ++--------
>  3 files changed, 16 insertions(+), 16 deletions(-)
> 
> diff --git a/arch/x86/kvm/hyperv.h b/arch/x86/kvm/hyperv.h
> index ddb1d0b019e6..75dcbe598fbc 100644
> --- a/arch/x86/kvm/hyperv.h
> +++ b/arch/x86/kvm/hyperv.h
> @@ -246,6 +246,18 @@ static inline int kvm_hv_verify_vp_assist(struct kvm_vcpu *vcpu)
>  	return kvm_hv_get_assist_page(vcpu);
>  }
>  
> +static inline void kvm_hv_nested_transtion_tlb_flush(struct kvm_vcpu *vcpu, bool tdp_enabled)
> +{
> +	/*
> +	 * KVM_REQ_HV_TLB_FLUSH flushes entries from either L1's VP_ID or
> +	 * L2's VP_ID upon request from the guest. Make sure we check for
> +	 * pending entries in the right FIFO upon L1/L2 transition as these
> +	 * requests are put by other vCPUs asynchronously.
> +	 */
> +	if (to_hv_vcpu(vcpu) && tdp_enabled)
> +		kvm_make_request(KVM_REQ_HV_TLB_FLUSH, vcpu);
> +}
> +
>  int kvm_hv_vcpu_flush_tlb(struct kvm_vcpu *vcpu);
>  
>  #endif
> diff --git a/arch/x86/kvm/svm/nested.c b/arch/x86/kvm/svm/nested.c
> index 3fea8c47679e..74c04102ef01 100644
> --- a/arch/x86/kvm/svm/nested.c
> +++ b/arch/x86/kvm/svm/nested.c
> @@ -487,14 +487,8 @@ static void nested_save_pending_event_to_vmcb12(struct vcpu_svm *svm,
>  
>  static void nested_svm_transition_tlb_flush(struct kvm_vcpu *vcpu)
>  {
> -	/*
> -	 * KVM_REQ_HV_TLB_FLUSH flushes entries from either L1's VP_ID or
> -	 * L2's VP_ID upon request from the guest. Make sure we check for
> -	 * pending entries in the right FIFO upon L1/L2 transition as these
> -	 * requests are put by other vCPUs asynchronously.
> -	 */
> -	if (to_hv_vcpu(vcpu) && npt_enabled)
> -		kvm_make_request(KVM_REQ_HV_TLB_FLUSH, vcpu);
> +	/* Handle pending Hyper-V TLB flush requests */
> +	kvm_hv_nested_transtion_tlb_flush(vcpu, npt_enabled);
>  
>  	/*
>  	 * TODO: optimize unconditional TLB flush/MMU sync.  A partial list of
> diff --git a/arch/x86/kvm/vmx/nested.c b/arch/x86/kvm/vmx/nested.c
> index c5ec0ef51ff7..382c0746d069 100644
> --- a/arch/x86/kvm/vmx/nested.c
> +++ b/arch/x86/kvm/vmx/nested.c
> @@ -1139,14 +1139,8 @@ static void nested_vmx_transition_tlb_flush(struct kvm_vcpu *vcpu,
>  {
>  	struct vcpu_vmx *vmx = to_vmx(vcpu);
>  
> -	/*
> -	 * KVM_REQ_HV_TLB_FLUSH flushes entries from either L1's VP_ID or
> -	 * L2's VP_ID upon request from the guest. Make sure we check for
> -	 * pending entries in the right FIFO upon L1/L2 transition as these
> -	 * requests are put by other vCPUs asynchronously.
> -	 */
> -	if (to_hv_vcpu(vcpu) && enable_ept)
> -		kvm_make_request(KVM_REQ_HV_TLB_FLUSH, vcpu);
> +	/* Handle pending Hyper-V TLB flush requests */
> +	kvm_hv_nested_transtion_tlb_flush(vcpu, enable_ept);
>  
>  	/*
>  	 * If vmcs12 doesn't use VPID, L1 expects linear and combined mappings


Reviewed-by: Maxim Levitsky <mlevitsk@...hat.com>

Best regards,
	Maxim Levitsky