On 08/21/2015 05:29 PM, Cornelia Huck wrote:
> On Fri, 21 Aug 2015 16:03:52 +0800
> Jason Wang <jasowang@xxxxxxxxxx> 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?
Yes.
>
>> */
>> @@ -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?
I think the answer depends on whether len == 0 is valid for ccw. If not
we can fail the assign earlier. Since even without this patch, if
userspace tries to register a dev with len equals to zero, it will also
be registered to KVM_FAST_MMIO_BUS. If yes, we need check as you
suggested here.
>
>> 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?
Good catch. I think keep the original code as is will be also ok to
solve this. (with changing the bus_idx to KVM_FAST_MMIO_BUS during
registering if it was an wildcard mmio).
>
>> kvm->buses[bus_idx]->ioeventfd_count--;
>> ioeventfd_release(p);
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