[pve-devel] [PATCH docs v4 4/5] added vIOMMU documentation

[Markus Frank <m.frank@proxmox.com>]

Signed-off-by: Markus Frank <m.frank@proxmox.com>
---
 qm-pci-passthrough.adoc | 25 +++++++++++++++++++++++++
 1 file changed, 25 insertions(+)

diff --git a/qm-pci-passthrough.adoc b/qm-pci-passthrough.adoc
index fa6ba35..7ed4d49 100644
--- a/qm-pci-passthrough.adoc
+++ b/qm-pci-passthrough.adoc
@@ -389,6 +389,31 @@ Example configuration with an `Intel GVT-g vGPU` (`Intel Skylake 6700k`):
 With this set, {pve} automatically creates such a device on VM start, and
 cleans it up again when the VM stops.
 
+[[qm_pci_viommu]]
+vIOMMU
+~~~~~~
+
+vIOMMU enables the option to passthrough pci devices to Level-2 VMs
+in Level-1 VMs via Nested Virtualisation.
+
+Host-Requirement: Set `intel_iommu=on` or `amd_iommu=on` depending on your
+CPU.
+
+VM-Requirement: For both Intel and AMD CPUs you will have to set
+`intel_iommu=on` as a Linux boot parameter in the vIOMMU-enabled-VM, because
+Qemu implements the Intel variant.
+
+To enable vIOMMU you have to add `viommu=1` to the machine-parameter in the
+VM-Configuration, of the VM that you want to be able to passthrough pci devices.
+
+----
+# qm set VMID -machine q35,viommu=1
+----
+
+Guest vIOMMU only works with the *q35* machine type and with *kvm* enabled.
+
+https://wiki.qemu.org/Features/VT-d
+
 ifdef::wiki[]
 
 See Also
-- 
2.30.2