kernel: iommu/vt-d: Disallow dirty tracking if incoherent page walk

A flaw was found in the Intel VT-d IOMMU support in the Linux kernel. When an IOMMU is configured to perform dirty-page tracking, but the page-walk memory region is incoherent between the IOMMU and CPU, the hardware may attempt to atomically update the bits in a paging-structure entry that is not...