Description of problem:
+++ This bug was initially created as a clone of Bug #753692 +++

1. During boot win2012 guest with 100 virtio network, it causes qemu-kvm show  the following information:
(qemu) qemu-kvm: virtio_pci_set_host_notifier_internal: unable to map ioeventfd: -28 
vhost VQ 1 notifier binding failed: 28

2. Boot win2012 guest with more than 200 virtio disks, cause qemu-kvm show the following information:
(qemu) qemu-kvm: virtio_pci_set_host_notifier_internal: unable to map ioeventfd: -28
qemu-kvm: virtio_pci_start_ioeventfd: failed. Fallback to a userspace (slower).

Version-Release number of selected component (if applicable):
kernel: 2.6.32-414.el6.x86_64
qemu-kvm: qemu-kvm-0.12.1.2-2.398.el6.x86_64

How reproducible:
100%

Steps to Reproduce:
1. Boot win2012 guest with 100 virtio network, the following command line:
in attachment virtio-network

2. Boot win2012 guest with more than 200 virtio disks
in attachment virtio-disks

3.

Actual results:
1. win2012 guest with 100 virtio network: 
(qemu) qemu-kvm: virtio_pci_set_host_notifier_internal: unable to map ioeventfd: -28
vhost VQ 1 notifier binding failed: 28

2. win2012 guest with more than 200 virtio disks
(qemu) qemu-kvm: virtio_pci_set_host_notifier_internal: unable to map ioeventfd: -28
qemu-kvm: virtio_pci_start_ioeventfd: failed. Fallback to a userspace (slower).

Expected results:
guest boot successful

Additional info: