[libvirt] Reboot with SR-IOV devices confuses IOMMU (bug #1294677)

[Jakub Kicinski]

On Tue, 29 Dec 2015 15:58:48 +0000, Jakub Kicinski wrote:
> Hi!
> 
> I hit an issue with PCI passthrough - after I reboot the VM IOMMU
> mappings are incorrect and devices will access invalid memory.
> [...]

Reproduced easily on fully up-to-date CentOS 7 with ixgbe (Intel's
10gig cards) on Ivy Bridge CPU:

CentOS Linux release 7.2.1511 (Core)

# rpm -q libvirt qemu-kvm kernel
libvirt-1.2.17-13.el7_2.2.x86_64
qemu-kvm-1.5.3-105.el7_2.1.x86_64
kernel-3.10.0-327.3.1.el7.x86_64