Re: [Qemu-devel] [PATCH v3 4/5] KVM: ioeventfd for virtio-ccw devices.

[Stefan Hajnoczi]

On Mon, Feb 25, 2013 at 04:27:49PM +0100, Cornelia Huck wrote:
> diff --git a/virt/kvm/eventfd.c b/virt/kvm/eventfd.c
> index f0ced1a..8de3cd7 100644
> --- a/virt/kvm/eventfd.c
> +++ b/virt/kvm/eventfd.c
> @@ -679,11 +679,16 @@ static int
>  kvm_assign_ioeventfd(struct kvm *kvm, struct kvm_ioeventfd *args)
>  {
>       int                       pio = args->flags & KVM_IOEVENTFD_FLAG_PIO;
> -     enum kvm_bus              bus_idx = pio ? KVM_PIO_BUS : KVM_MMIO_BUS;
> +     int                       ccw;
> +     enum kvm_bus              bus_idx;
>       struct _ioeventfd        *p;
>       struct eventfd_ctx       *eventfd;
>       int                       ret;
>  
> +     ccw = args->flags & KVM_IOEVENTFD_FLAG_VIRTIO_CCW_NOTIFY;
> +     bus_idx = pio ? KVM_PIO_BUS :
> +             ccw ? KVM_VIRTIO_CCW_NOTIFY_BUS :
> +             KVM_MMIO_BUS;
>       /* must be natural-word sized */
>       switch (args->len) {
>       case 1:
> @@ -759,11 +764,16 @@ static int
>  kvm_deassign_ioeventfd(struct kvm *kvm, struct kvm_ioeventfd *args)
>  {
>       int                       pio = args->flags & KVM_IOEVENTFD_FLAG_PIO;
> -     enum kvm_bus              bus_idx = pio ? KVM_PIO_BUS : KVM_MMIO_BUS;
> +     int                       ccw;
> +     enum kvm_bus              bus_idx;
>       struct _ioeventfd        *p, *tmp;
>       struct eventfd_ctx       *eventfd;
>       int                       ret = -ENOENT;
>  
> +     ccw = args->flags & KVM_IOEVENTFD_FLAG_VIRTIO_CCW_NOTIFY;
> +     bus_idx = pio ? KVM_PIO_BUS :
> +             ccw ? KVM_VIRTIO_CCW_NOTIFY_BUS :
> +             KVM_MMIO_BUS;

This is getting pretty convoluted.  Drop of pio and ccw local variables,
replace ?: with an if statement:

if (args->flags & KVM_IOEVENTFD_FLAG_VIRTIO_CCW_NOTIFY)
        bus_idx = KVM_VIRTIO_CCW_NOTIFY_BUS;
else if (args->flags & KVM_IOEVENTFD_FLAG_PIO)
        bus_idx = KVM_PIO_BUS;
else
        bus_idx = KVM_MMIO_BUS;