I'm trying out Parallels Workstation Extreme because I need VGA passthrough, and under File -> Preferences -> Intel VT-d I see a message saying that Initialization of Intel VT-d failed because the DMAR ACPI table could not be found. But dmesg shows: Intel-IOMMU: enabled [...] ACPI: RSDP 00000000000f9f70 00024 (v02 ACPIAM) ACPI: XSDT 00000000af790100 00064 (v01 042413 XSDT1438 20130424 MSFT 00000097) [...] ACPI: DMAR 00000000af79e0d0 00128 (v01 AMI OEMDMAR 00000001 MSFT 00000097) When prl_hypervisor is loading, I it shows this: prl_hypervisor: module license 'unspecified' taints kernel. Disabling lock debugging due to kernel taint /drv/ HypVtx.c:186 CPU is Intel /drv/ HypLowCache.c:193 Low cache initialized (0 kB for 0 VMs on 48452 MB) /drv/ HypApic.c:247 Host APIC base_msr 0xFEE00800 ver 0x15 /drv/ HypVtd.c:3964 [vtdInit] /drv/ HypAcpi.c:160 map: addr = 0x9d000, size = 1024 /drv/ HypAcpi.c:111 [acpiScanForRsdp] RSDP NOT found! ioremap error for 0xaf790000-0xaf791000, requested 0x10, got 0x0 /drv/ HypAcpi.c:241 [acpiMapTable] Can't map physical address 0x00000000af790100(36)! /drv/ HypAcpi.c:351 [_acpiFindTableBySig] Can't map RSDT/XSDT table! /drv/ HypVtd.c:3709 [vtdProcessDmarTable] Can't find DMAR table! /drv/ HypVtd.c:4005 [vtdInit] No VT-d hardware So the kernel is showing that the required ACPI tables are there, but prl_hypervisor is claiming they aren't. What is going on here? I am using EL6 kernel 2.6.32-358.6.1.el6.x86_64, am using the following boot parameters: selinux=0 intel_iommu=on iomem=relaxed The CPU is a Xeon X5650 and the hardware supports VT-d (I can successfully pass PCI devices through to VMs using Xen and KVM). Googling the problem has yielded several similar posts, but no resolution was ever provided. I also tried with intel_iommu=off intremap=off kernel boot parameters and it made no difference.