linux-kernel - Re: [PATCH 01/10] KVM: nVMX: Move reflection check into nested_vmx_reflect

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Message-ID: <87k13opi6m.fsf@vitty.brq.redhat.com>
Date:   Fri, 13 Mar 2020 13:12:33 +0100
From:   Vitaly Kuznetsov <vkuznets@...hat.com>
To:     Sean Christopherson <sean.j.christopherson@...el.com>
Cc:     Paolo Bonzini <pbonzini@...hat.com>,
        Wanpeng Li <wanpengli@...cent.com>,
        Jim Mattson <jmattson@...gle.com>,
        Joerg Roedel <joro@...tes.org>, kvm@...r.kernel.org,
        linux-kernel@...r.kernel.org, Xiaoyao Li <xiaoyao.li@...el.com>
Subject: Re: [PATCH 01/10] KVM: nVMX: Move reflection check into nested_vmx_reflect_vmexit()

Sean Christopherson <sean.j.christopherson@...el.com> writes:

> Move the call to nested_vmx_exit_reflected() from vmx_handle_exit() into
> nested_vmx_reflect_vmexit() and change the semantics of the return value
> for nested_vmx_reflect_vmexit() to indicate whether or not the exit was
> reflected into L1.  nested_vmx_exit_reflected() and
> nested_vmx_reflect_vmexit() are intrinsically tied together, calling one
> without simultaneously calling the other makes little sense.
>
> No functional change intended.
>
> Signed-off-by: Sean Christopherson <sean.j.christopherson@...el.com>
> ---
>  arch/x86/kvm/vmx/nested.h | 16 +++++++++++-----
>  arch/x86/kvm/vmx/vmx.c    |  4 ++--
>  2 files changed, 13 insertions(+), 7 deletions(-)
>
> diff --git a/arch/x86/kvm/vmx/nested.h b/arch/x86/kvm/vmx/nested.h
> index 21d36652f213..6bc379cf4755 100644
> --- a/arch/x86/kvm/vmx/nested.h
> +++ b/arch/x86/kvm/vmx/nested.h
> @@ -72,12 +72,16 @@ static inline bool nested_ept_ad_enabled(struct kvm_vcpu *vcpu)
>  }
>  
>  /*
> - * Reflect a VM Exit into L1.
> + * Conditionally reflect a VM-Exit into L1.  Returns %true if the VM-Exit was
> + * reflected into L1.
>   */
> -static inline int nested_vmx_reflect_vmexit(struct kvm_vcpu *vcpu,
> -					    u32 exit_reason)
> +static inline bool nested_vmx_reflect_vmexit(struct kvm_vcpu *vcpu,
> +					     u32 exit_reason)
>  {
> -	u32 exit_intr_info = vmcs_read32(VM_EXIT_INTR_INFO);
> +	u32 exit_intr_info;
> +
> +	if (!nested_vmx_exit_reflected(vcpu, exit_reason))
> +		return false;

(unrelated to your patch)

It's probably just me but 'nested_vmx_exit_reflected()' name always
makes me thinkg 'the vmexit WAS [already] reflected' and not 'the vmexit
NEEDS to be reflected'. 'nested_vmx_exit_needs_reflecting()' maybe?

>  
>  	/*
>  	 * At this point, the exit interruption info in exit_intr_info
> @@ -85,6 +89,8 @@ static inline int nested_vmx_reflect_vmexit(struct kvm_vcpu *vcpu,
>  	 * we need to query the in-kernel LAPIC.
>  	 */
>  	WARN_ON(exit_reason == EXIT_REASON_EXTERNAL_INTERRUPT);
> +
> +	exit_intr_info = vmcs_read32(VM_EXIT_INTR_INFO);
>  	if ((exit_intr_info &
>  	     (INTR_INFO_VALID_MASK | INTR_INFO_DELIVER_CODE_MASK)) ==
>  	    (INTR_INFO_VALID_MASK | INTR_INFO_DELIVER_CODE_MASK)) {
> @@ -96,7 +102,7 @@ static inline int nested_vmx_reflect_vmexit(struct kvm_vcpu *vcpu,
>  
>  	nested_vmx_vmexit(vcpu, exit_reason, exit_intr_info,
>  			  vmcs_readl(EXIT_QUALIFICATION));
> -	return 1;
> +	return true;
>  }
>  
>  /*
> diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c
> index 57742ddfd854..c1caac7e8f57 100644
> --- a/arch/x86/kvm/vmx/vmx.c
> +++ b/arch/x86/kvm/vmx/vmx.c
> @@ -5863,8 +5863,8 @@ static int vmx_handle_exit(struct kvm_vcpu *vcpu,
>  	if (vmx->emulation_required)
>  		return handle_invalid_guest_state(vcpu);
>  
> -	if (is_guest_mode(vcpu) && nested_vmx_exit_reflected(vcpu, exit_reason))
> -		return nested_vmx_reflect_vmexit(vcpu, exit_reason);
> +	if (is_guest_mode(vcpu) && nested_vmx_reflect_vmexit(vcpu, exit_reason))
> +		return 1;
>  
>  	if (exit_reason & VMX_EXIT_REASONS_FAILED_VMENTRY) {
>  		dump_vmcs();

Reviewed-by: Vitaly Kuznetsov <vkuznets@...hat.com>

-- 
Vitaly