When follow How to assign devices with VT-d in KVM tutorial in KVM site, you may encounter qemu-system-x86_64complains:
......No IOMMU found. Unable to assign device......
The root cause is the KVM_DEVICE_ASSIGNMENT configuration option is deprecated, and the code in kernel KVM part is like this:
#ifdef CONFIG_KVM_DEVICE_ASSIGNMENT
case KVM_CAP_IOMMU:
r = iommu_present(&pci_bus_type);
break;
#endif
So you should use VFIO feature instead.
If you still to want to use KVM_DEVICE_ASSIGNMENT feature, please rebuild the kernel with KVM_DEVICE_ASSIGNMENT option on.
Reference:
A question about “CONFIGKVMDEVICE_ASSIGNMENT” configuration