[[qm_pci_passthrough]]
PCI(e) Passthrough
------------------
+ifdef::wiki[]
+:pve-toplevel:
+endif::wiki[]
PCI(e) passthrough is a mechanism to give a virtual machine control over
a PCI device from the host. This can have some advantages over using
some configuration to enable PCI(e) passthrough.
-IOMMU
-+++++
+.IOMMU
The IOMMU has to be activated on the kernel commandline. The easiest way is to
-enable trough grub. Edit `'/etc/default/grub'' and add the following to th
+enable trough grub. Edit `'/etc/default/grub'' and add the following to the
'GRUB_CMDLINE_LINUX_DEFAULT' variable:
* for Intel CPUs:
amd_iommu=on
----
+[[qm_pci_passthrough_update_grub]]
To bring this change in effect, make sure you run:
----
# update-grub
----
-Kernel Modules
-++++++++++++++
+.Kernel Modules
You have to make sure the following modules are loaded. This can be achieved by
adding them to `'/etc/modules''
# update-initramfs -u -k all
----
-Finish Configuration
-++++++++++++++++++++
+.Finish Configuration
Finally reboot to bring the changes into effect and check that it is indeed
enabled.
----
-# dmesg -e DMAR -e IOMMU -e AMD-Vi
+# dmesg | grep -e DMAR -e IOMMU -e AMD-Vi
----
should display that `IOMMU`, `Directed I/O` or `Interrupt Remapping` is
Please be aware that this option can make your system unstable.
====
+GPU Passthrough Notes
+^^^^^^^^^^^^^^^^^^^^^
+
+It is not possible to display the frame buffer of the GPU via NoVNC or SPICE on
+the {pve} web interface.
+
+When passing through a whole GPU or a vGPU and graphic output is wanted, one
+has to either physically connect a monitor to the card, or configure a remote
+desktop software (for example, VNC or RDP) inside the guest.
+
+If you want to use the GPU as a hardware accelerator, for example, for
+programs using OpenCL or CUDA, this is not required.
+
Host Device Passthrough
~~~~~~~~~~~~~~~~~~~~~~~
# qm set VMID -hostpci0 00:02.0
----
-If your device has multiple functions, you can pass them through all together
-with the shortened syntax ``00:02`'
+If your device has multiple functions (e.g., ``00:02.0`' and ``00:02.1`' ),
+you can pass them through all together with the shortened syntax ``00:02`'
There are some options to which may be necessary, depending on the device
and guest OS:
* *romfile=<path>*, is an optional path to a ROM file for the device to use.
This is a relative path under */usr/share/kvm/*.
-Example
-+++++++
+.Example
An example of PCIe passthrough with a GPU set to primary:
----
+
To make this change persistent you can use the `sysfsutils` Debian package.
-After installation configure it via */etc/sysfs.conf* or a `FILE.conf' inf
+After installation configure it via */etc/sysfs.conf* or a `FILE.conf' in
*/etc/sysfs.d/*.
VM Configuration
to enable this feature in the BIOS/EFI first, or to use a specific PCI(e) port
for it to work. In doubt, consult the manual of the platform or contact its
vendor.
+
+Mediated Devices (vGPU, GVT-g)
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+Mediated devices are another method to use reuse features and performance from
+physical hardware for virtualized hardware. These are found most common in
+virtualized GPU setups such as Intels GVT-g and Nvidias vGPUs used in their
+GRID technology.
+
+With this, a physical Card is able to create virtual cards, similar to SR-IOV.
+The difference is that mediated devices do not appear as PCI(e) devices in the
+host, and are such only suited for using in virtual machines.
+
+
+Host Configuration
+^^^^^^^^^^^^^^^^^^
+
+In general your card's driver must support that feature, otherwise it will
+not work. So please refer to your vendor for compatbile drivers and how to
+configure them.
+
+Intels drivers for GVT-g are integraded in the Kernel and should work
+with the 5th, 6th and 7th generation Intel Core Processors, further E3 v4, E3
+v5 and E3 v6 Xeon Processors are supported.
+
+To enable it for Intel Graphcs, you have to make sure to load the module
+'kvmgt' (for example via `/etc/modules`) and to enable it on the Kernel
+commandline. For this you can edit `'/etc/default/grub'' and add the following
+to the 'GRUB_CMDLINE_LINUX_DEFAULT' variable:
+
+----
+ i915.enable_gvt=1
+----
+
+After that remember to
+xref:qm_pci_passthrough_update_initramfs[update the `initramfs`],
+xref:qm_pci_passthrough_update_grub[update grub] and
+reboot your host.
+
+VM Configuration
+^^^^^^^^^^^^^^^^
+
+To use a mediated device, simply specify the `mdev` property on a `hostpciX`
+VM configuration option.
+
+You can get the supported devices via the 'sysfs'. For example, to list the
+supported types for the device '0000:00:02.0' you would simply execute:
+
+----
+# ls /sys/bus/pci/devices/0000:00:02.0/mdev_supported_types
+----
+
+Each entry is a directory which contains the following important files:
+
+* 'available_instances' contains the amount of still available instances of
+this type, each 'mdev' use in a VM reduces this.
+* 'description' contains a short description about the capabilities of the type
+* 'create' is the endpoint to create such a device, {pve} does this
+automatically for you, if a 'hostpciX' option with `mdev` is configured.
+
+Example configuration with an `Intel GVT-g vGPU` (`Intel Skylake 6700k`):
+
+----
+# qm set VMID -hostpci0 00:02.0,mdev=i915-GVTg_V5_4
+----
+
+With this set, {pve} automatically creates such a device on VM start, and
+cleans it up again when the VM stops.
+
+ifdef::wiki[]
+
+See Also
+~~~~~~~~
+
+* link:/wiki/Pci_passthrough[PCI Passthrough Examples]
+
+endif::wiki[]
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