linux-kernel - Re: [PATCH 07/10] KVM: nVMX: Cast exit_reason to u16 to check for nested EXTERNAL

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Date:   Fri, 13 Mar 2020 14:56:55 +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 07/10] KVM: nVMX: Cast exit_reason to u16 to check for nested EXTERNAL_INTERRUPT

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

> Explicitly check only the basic exit reason when emulating an external
> interrupt VM-Exit in nested_vmx_vmexit().  Checking the full exit reason
> doesn't currently cause problems, but only because the only exit reason
> modifier support by KVM is FAILED_VMENTRY, which is mutually exclusive
> with EXTERNAL_INTERRUPT.  Future modifiers, e.g. ENCLAVE_MODE, will
> coexist with EXTERNAL_INTERRUPT.
>
> Signed-off-by: Sean Christopherson <sean.j.christopherson@...el.com>
> ---
>  arch/x86/kvm/vmx/nested.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/arch/x86/kvm/vmx/nested.c b/arch/x86/kvm/vmx/nested.c
> index 8fbbe2152ab7..86b12a2918c5 100644
> --- a/arch/x86/kvm/vmx/nested.c
> +++ b/arch/x86/kvm/vmx/nested.c
> @@ -4337,7 +4337,7 @@ void nested_vmx_vmexit(struct kvm_vcpu *vcpu, u32 exit_reason,
>  	vcpu->arch.mp_state = KVM_MP_STATE_RUNNABLE;
>  
>  	if (likely(!vmx->fail)) {
> -		if (exit_reason == EXIT_REASON_EXTERNAL_INTERRUPT &&
> +		if ((u16)exit_reason == EXIT_REASON_EXTERNAL_INTERRUPT &&
>  		    nested_exit_intr_ack_set(vcpu)) {
>  			int irq = kvm_cpu_get_interrupt(vcpu);
>  			WARN_ON(irq < 0);

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

-- 
Vitaly