Re: [PATCH 4/4] KVM/VMX: Fold handle_interrupt_nmi_irqoff() into its solo caller

[Paolo Bonzini]

On 30/04/21 11:03, Thomas Gleixner wrote:
> Lai,
>
> On Tue, Apr 27 2021 at 07:09, Lai Jiangshan wrote:
> >   	u32 intr_info = vmx_get_intr_info(&vmx->vcpu);
> > @@ -6427,12 +6417,19 @@ static void handle_exception_nmi_irqoff(struct vcpu_vmx *vmx)
> >   static void handle_external_interrupt_irqoff(struct kvm_vcpu *vcpu)
> >   {
> >   	u32 intr_info = vmx_get_intr_info(vcpu);
> > +	unsigned int vector;
> > +	gate_desc *desc;
> >   
> >   	if (WARN_ONCE(!is_external_intr(intr_info),
> >   	    "KVM: unexpected VM-Exit interrupt info: 0x%x", intr_info))
> >   		return;
> >   
> > -	handle_interrupt_nmi_irqoff(vcpu, intr_info);
> > +	vector = intr_info & INTR_INFO_VECTOR_MASK;
> > +	desc = (gate_desc *)host_idt_base + vector;
> > +
> > +	kvm_before_interrupt(vcpu);
> > +	vmx_do_interrupt_nmi_irqoff(gate_offset(desc));
> > +	kvm_after_interrupt(vcpu);
>
> So the previous patch does:
>
> +               kvm_before_interrupt(&vmx->vcpu);
> +               vmx_do_interrupt_nmi_irqoff((unsigned long)asm_noist_exc_nmi);
> +               kvm_after_interrupt(&vmx->vcpu);
>
> What is this idt gate descriptor dance for in this code?

NMIs are sent through a different vmexit code (the same one as 
exceptions).  This one is for interrupts.

Paolo