Re: [PATCH 4.19 08/57] KVM: x86: Fix split-irqchip vs interrupt injection window request

[Paolo Bonzini]

On 01/12/20 16:33, Pavel Machek wrote:
> Hi!
>
> > - in order to tell userspace we will inject its interrupt ("IRQ
> >    window open" i.e. kvm_vcpu_ready_for_interrupt_injection), both
> >    KVM and the vCPU need to be ready to accept the interrupt.
> >
> > ... and this is what the patch implements.
> >
> > Reported-by: David Woodhouse <dwmw@xxxxxxxxxxxx>
> > Analyzed-by: David Woodhouse <dwmw@xxxxxxxxxxxx>
> > Cc: stable@xxxxxxxxxxxxxxx
>
> This makes no difference for -stable, but the patch is confused about
> types:
>
> > +++ b/arch/x86/kvm/x86.c
> > @@ -3351,21 +3351,23 @@ static int kvm_vcpu_ioctl_set_lapic(stru
> >   
> >   static int kvm_cpu_accept_dm_intr(struct kvm_vcpu *vcpu)
> >   {
> > +	/*
> > +	 * We can accept userspace's request for interrupt injection
> > +	 * as long as we have a place to store the interrupt number.
> > +	 * The actual injection will happen when the CPU is able to
> > +	 * deliver the interrupt.
> > +	 */
> > +	if (kvm_cpu_has_extint(vcpu))
> > +		return false;
>
> Since function is "static int" it should probably return 0.

Other way round, it should return static bool. :)  At least it's 
consistently returning a boolean expression, never e.g. negative errno.

Paolo