Re: [PATCH v5 4/4] KVM: x86: Add support for local interrupt requests from userspace

[Paolo Bonzini <pbonzini@redhat.com>]

On 28/07/2015 01:17, Steve Rutherford wrote:
>  	return kvm->arch.vpic;
>  }
>  
> +static inline int pic_in_kernel(struct kvm *kvm)
> +{
> +	int ret;
> +
> +	ret = (pic_irqchip(kvm) != NULL);
> +	smp_rmb();

What does this memory barrier pair with?  I don't think it's necessary.

> +	return ret;
> +}
> +
>  static inline int irqchip_split(struct kvm *kvm)
>  {
>  	return kvm->arch.irqchip_split;


> @@ -5819,13 +5828,24 @@ static void post_kvm_run_save(struct kvm_vcpu *vcpu)
>  	kvm_run->flags = is_smm(vcpu) ? KVM_RUN_X86_SMM : 0;
>  	kvm_run->cr8 = kvm_get_cr8(vcpu);
>  	kvm_run->apic_base = kvm_get_apic_base(vcpu);
> -	if (irqchip_in_kernel(vcpu->kvm))
> +	if (irqchip_in_kernel(vcpu->kvm) && pic_in_kernel(vcpu->kvm))
>  		kvm_run->ready_for_interrupt_injection = 1;
> -	else
> +	else if (irqchip_in_kernel(vcpu->kvm)) {
> +		int ready_for_interrupt_injection =
> +				kvm_apic_accept_pic_intr(vcpu);
> +
> +		if (!kvm_run->ready_for_interrupt_injection &&
> +		    ready_for_interrupt_injection)
> +			kvm_make_request(KVM_REQ_PIC_UNMASK_EXIT, vcpu);
> +
> +		kvm_run->ready_for_interrupt_injection =
> +				ready_for_interrupt_injection;
> +	} else {
>  		kvm_run->ready_for_interrupt_injection =
>  			kvm_arch_interrupt_allowed(vcpu) &&
>  			!kvm_cpu_has_interrupt(vcpu) &&
>  			!kvm_event_needs_reinjection(vcpu);
> +	}
>  }
>  
>  static void update_cr8_intercept(struct kvm_vcpu *vcpu)

Why is this necessary?  Could it just set
kvm_run->ready_for_interrupt_injection as in the pic_in_kernel case?

Paolo