On Fri, 21 Aug 2015 16:03:52 +0800
Jason Wang <[email protected]> wrote:


> diff --git a/virt/kvm/eventfd.c b/virt/kvm/eventfd.c
> index 9ff4193..834a409 100644
> --- a/virt/kvm/eventfd.c
> +++ b/virt/kvm/eventfd.c
> @@ -838,11 +838,6 @@ kvm_assign_ioeventfd(struct kvm *kvm, struct 
> kvm_ioeventfd *args)
>  
>       kvm_iodevice_init(&p->dev, &ioeventfd_ops);
>  
> -     ret = kvm_io_bus_register_dev(kvm, bus_idx, p->addr, p->length,
> -                                   &p->dev);
> -     if (ret < 0)
> -             goto unlock_fail;
> -
>       /* When length is ignored, MMIO is also put on a separate bus, for
>        * faster lookups.

You probably want to change this comment as well?

>        */
> @@ -850,9 +845,15 @@ kvm_assign_ioeventfd(struct kvm *kvm, struct 
> kvm_ioeventfd *args)

Unfortunately snipped by diff, but the check here is on !len && !PIO,
which only does the desired thing as VIRTIO_CCW always uses len == 8.
Should the check be for !len && MMIO instead?

>               ret = kvm_io_bus_register_dev(kvm, KVM_FAST_MMIO_BUS,
>                                             p->addr, 0, &p->dev);
>               if (ret < 0)
> -                     goto register_fail;
> +                     goto unlock_fail;
> +     } else {
> +             ret = kvm_io_bus_register_dev(kvm, bus_idx, p->addr, p->length,
> +                                           &p->dev);
> +             if (ret < 0)
> +                     goto unlock_fail;
>       }

Hm... maybe the following would be more obvious:

my_bus = (p->length == 0) && (bus_idx == KVM_MMIO_BUS) ? KVM_FAST_MMIO_BUS : 
bus_idx;
ret = kvm_io_bus_register_dev(kvm, my_bus, p->addr, p->length, &pdev->dev); 

>  
> +
>       kvm->buses[bus_idx]->ioeventfd_count++;
>       list_add_tail(&p->list, &kvm->ioeventfds);

(...)

> @@ -900,10 +899,11 @@ kvm_deassign_ioeventfd(struct kvm *kvm, struct 
> kvm_ioeventfd *args)
>               if (!p->wildcard && p->datamatch != args->datamatch)
>                       continue;
>  
> -             kvm_io_bus_unregister_dev(kvm, bus_idx, &p->dev);
>               if (!p->length) {
>                       kvm_io_bus_unregister_dev(kvm, KVM_FAST_MMIO_BUS,
>                                                 &p->dev);
> +             } else {
> +                     kvm_io_bus_unregister_dev(kvm, bus_idx, &p->dev);
>               }

Similar comments here... do you want to check for bus_idx ==
KVM_MMIO_BUS as well?

>               kvm->buses[bus_idx]->ioeventfd_count--;
>               ioeventfd_release(p);

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