From d5b75187dbddae6453cfbdf0822763573825fb6c Mon Sep 17 00:00:00 2001 From: Markus Frank Date: Thu, 11 Apr 2024 12:48:21 +0200 Subject: [PATCH] add vIOMMU documentation Signed-off-by: Markus Frank --- qm-pci-passthrough.adoc | 50 +++++++++++++++++++++++++++++++++++++++++ qm.adoc | 1 + 2 files changed, 51 insertions(+) diff --git a/qm-pci-passthrough.adoc b/qm-pci-passthrough.adoc index 3abeb50..bbd6b85 100644 --- a/qm-pci-passthrough.adoc +++ b/qm-pci-passthrough.adoc @@ -499,6 +499,56 @@ properly used with HA and hardware changes are detected and non root users can configure them. See xref:resource_mapping[Resource Mapping] for details on that. +[[qm_pci_viommu]] +vIOMMU (emulated IOMMU) +~~~~~~~~~~~~~~~~~~~~~~~ + +vIOMMU is the emulation of a hardware IOMMU within a virtual machine, providing +improved memory access control and security for virtualized I/O devices. Using +the vIOMMU option also allows you to pass through PCI devices to level-2 VMs in +level-1 VMs via https://pve.proxmox.com/wiki/Nested_Virtualization[Nested Virtualization]. +There are currently two vIOMMU implementations available: Intel and VirtIO. + +Host requirement: + +* Add `intel_iommu=on` or `amd_iommu=on` depending on your CPU to your kernel +command line. + +Intel vIOMMU +^^^^^^^^^^^^ + +Intel vIOMMU specific VM requirements: + +* Whether you are using an Intel or AMD CPU on your host, it is important to set +`intel_iommu=on` in the VMs kernel parameters. + +* To use Intel vIOMMU you need to set *q35* as the machine type. + +If all requirements are met, you can add `viommu=intel` to the machine parameter +in the configuration of the VM that should be able to pass through PCI devices. + +---- +# qm set VMID -machine q35,viommu=intel +---- + +https://wiki.qemu.org/Features/VT-d[QEMU documentation for VT-d] + +VirtIO vIOMMU +^^^^^^^^^^^^^ + +This vIOMMU implementation is more recent and does not have as many limitations +as Intel vIOMMU but is currently less used in production and less documentated. + +With VirtIO vIOMMU there is *no* need to set any kernel parameters. It is also +*not* necessary to use q35 as the machine type, but it is advisable if you want +to use PCIe. + +---- +# qm set VMID -machine q35,viommu=virtio +---- + +https://web.archive.org/web/20230804075844/https://michael2012z.medium.com/virtio-iommu-789369049443[Blog-Post by Michael Zhao explaining virtio-iommu] + ifdef::wiki[] See Also diff --git a/qm.adoc b/qm.adoc index 91f3617..45e3a57 100644 --- a/qm.adoc +++ b/qm.adoc @@ -152,6 +152,7 @@ https://en.wikipedia.org/wiki/Intel_440FX[Intel 440FX] or the https://ark.intel.com/content/www/us/en/ark/products/31918/intel-82q35-graphics-and-memory-controller.html[Q35] chipset, which also provides a virtual PCIe bus, and thus may be desired if you want to pass through PCIe hardware. +Additionally, you can select a xref:qm_pci_viommu[vIOMMU] implementation. Machine Version +++++++++++++++