fix some typos like s/seperate/separate/ passhtrough, ...
Reword some sentences, try to reduces commas per sentence (while I
like them, others don't and they entangle your mind when reading a
bit).
Try to improve formatting, adding some emphasis on abbrevations or
other important things. Ensur all abbrev. are writen uppercase.
Signed-off-by: Thomas Lamprecht <t.lamprecht@proxmox.com>
------------------
PCI(e) passthrough is a mechanism to give a virtual machine control over
------------------
PCI(e) passthrough is a mechanism to give a virtual machine control over
-a pci device usually only available for the host. This can have some
-advantages over using virtualized hardware, for example lower latency,
-higher performance, or more features (e.g., offloading).
+a PCI device from the host. This can have some advantages over using
+virtualized hardware, for example lower latency, higher performance, or more
+features (e.g., offloading).
-If you pass through a device to a virtual machine, you cannot use that
+But, if you pass through a device to a virtual machine, you cannot use that
device anymore on the host or in any other VM.
General Requirements
~~~~~~~~~~~~~~~~~~~~
Since passthrough is a feature which also needs hardware support, there are
device anymore on the host or in any other VM.
General Requirements
~~~~~~~~~~~~~~~~~~~~
Since passthrough is a feature which also needs hardware support, there are
-some requirements and steps before it can work.
+some requirements to check and preparations to be done to make it work.
+
+Your hardware needs to support `IOMMU` (*I*/*O* **M**emory **M**anagement
+**U**nit) interrupt remapping, this includes the CPU and the mainboard.
-Your hardware has to support IOMMU interrupt remapping, this includes CPU and
-Mainboard.
-
-Generally Intel systems with VT-d, and AMD systems with AMD-Vi support this,
-but it is not guaranteed that everything will work out of the box, due
-to bad hardware implementation or missing/low quality drivers.
+Generally, Intel systems with VT-d, and AMD systems with AMD-Vi support this.
+But it is not guaranteed that everything will work out of the box, due
+to bad hardware implementation and missing or low quality drivers.
-In most cases, server grade hardware has better support than consumer grade
+Further, server grade hardware has often better support than consumer grade
hardware, but even then, many modern system can support this.
hardware, but even then, many modern system can support this.
-Please refer to your hardware vendor if this is a feature that is supported
-under Linux.
+Please refer to your hardware vendor to check if they support this feature
+under Linux for your specific setup
+
Configuration
^^^^^^^^^^^^^
Configuration
^^^^^^^^^^^^^
-To enable PCI(e) passthrough, there are some configurations needed.
+Once you ensured that your hardware supports passthrough, you will need to do
+some configuration to enable PCI(e) passthrough.
-First, the iommu has to be activated on the kernel commandline.
-The easiest way is to enable it in */etc/default/grub*. Just add
-or if you have AMD hardware:
+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
+'GRUB_CMDLINE_LINUX_DEFAULT' variable:
+* for Intel CPUs:
++
+----
+ intel_iommu=on
+----
+* for AMD CPUs:
++
+----
-to GRUB_CMDLINE_LINUX_DEFAULT
+To bring this change in effect, make sure you run:
+
+----
+# update-grub
+----
-After that, make sure you run 'update grub' to update grub.
+Kernel Modules
+++++++++++++++
-Second, you have to make sure the following modules are loaded.
-This can be achieved by adding them to */etc/modules*
+You have to make sure the following modules are loaded. This can be achieved by
+adding them to `'/etc/modules''
vfio
vfio_iommu_type1
vfio_pci
vfio_virqfd
vfio
vfio_iommu_type1
vfio_pci
vfio_virqfd
+[[qm_pci_passthrough_update_initramfs]]
After changing anything modules related, you need to refresh your
After changing anything modules related, you need to refresh your
+`initramfs`. On {pve} this can be done by executing:
-update-initramfs -u -k all
+# update-initramfs -u -k all
-Finally reboot and check that it is indeed enabled.
+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 -e DMAR -e IOMMU -e AMD-Vi
-should display that IOMMU, Directed I/O or Interrupt Remapping is enabled.
-(The exact message can vary, depending on hardware and kernel version)
+should display that `IOMMU`, `Directed I/O` or `Interrupt Remapping` is
+enabled, depending on hardware and kernel the exact message can vary.
It is also important that the device(s) you want to pass through
It is also important that the device(s) you want to pass through
-are in a seperate IOMMU group. This can be checked with:
+are in a *separate* `IOMMU` group. This can be checked with:
-find /sys/kernel/iommu_groups/ -type l
+# find /sys/kernel/iommu_groups/ -type l
-It is okay if the device is in an IOMMU group together with its functions
+It is okay if the device is in an `IOMMU` group together with its functions
(e.g. a GPU with the HDMI Audio device) or with its root port or PCI(e) bridge.
.PCI(e) slots
[NOTE]
====
(e.g. a GPU with the HDMI Audio device) or with its root port or PCI(e) bridge.
.PCI(e) slots
[NOTE]
====
-Some platforms handle their PCI(e) slots differently, so if you
-do not get the desired IOMMU group separation, it may be helpful to
-try to put the card in a another PCI(e) slot.
+Some platforms handle their physical PCI(e) slots differently. So, sometimes
+it can help to put the card in a another PCI(e) slot, if you do not get the
+desired `IOMMU` group separation.
====
.Unsafe interrupts
[NOTE]
====
For some platforms, it may be necessary to allow unsafe interrupts.
====
.Unsafe interrupts
[NOTE]
====
For some platforms, it may be necessary to allow unsafe interrupts.
-This can most easily enabled with adding the following line
-in a .conf file in */etc/modprobe.d/*.
+For this add the following line in a file ending with `.conf' file in
+*/etc/modprobe.d/*:
options vfio_iommu_type1 allow_unsafe_interrupts=1
options vfio_iommu_type1 allow_unsafe_interrupts=1
Please be aware that this option can make your system unstable.
====
Please be aware that this option can make your system unstable.
====
~~~~~~~~~~~~~~~~~~~~~~~
The most used variant of PCI(e) passthrough is to pass through a whole
~~~~~~~~~~~~~~~~~~~~~~~
The most used variant of PCI(e) passthrough is to pass through a whole
-PCI(e) card, for example a GPU or network card.
+PCI(e) card, for example a GPU or a network card.
+
Host Configuration
^^^^^^^^^^^^^^^^^^
Host Configuration
^^^^^^^^^^^^^^^^^^
-In this case, the host can not use the card. This can be achieved by two
-methods:
-
-Either add the ids to the options of the vfio-pci modules. This works
-with adding
+In this case, the host cannot use the card. There are two methods to achieve
+this:
+* pass the device IDs to the options of the 'vfio-pci' modules by adding
++
+----
options vfio-pci ids=1234:5678,4321:8765
options vfio-pci ids=1234:5678,4321:8765
-
-to a .conf file in */etc/modprobe.d/* where 1234:5678 and 4321:8765 are
-the vendor and device ids obtained by:
-
++
+to a .conf file in */etc/modprobe.d/* where `1234:5678` and `4321:8765` are
+the vendor and device IDs obtained by:
++
+----
+# lcpci -nn
-Or simply blacklist the driver completely on the host with
-
+* blacklist the driver completely on the host, ensuring that it is free to bind
+for passthrough, with
++
+----
+----
++
+in a .conf file in */etc/modprobe.d/*.
-also in a .conf file in */etc/modprobe.d/*. Again update the initramfs
-and reboot after that.
+For both methods you need to
+xref:qm_pci_passthrough_update_initramfs[update the `initramfs`] again and
+reboot after that.
+[[qm_pci_passthrough_vm_config]]
VM Configuration
^^^^^^^^^^^^^^^^
VM Configuration
^^^^^^^^^^^^^^^^
-
-To pass through the device you set *hostpciX* on the VM with
+To pass through the device you need to set the *hostpciX* option in the VM
+configuration, for example by executing:
-qm set VMID -hostpci0 00:02.0
+# qm set VMID -hostpci0 00:02.0
----
If your device has multiple functions, you can pass them through all together
----
If your device has multiple functions, you can pass them through all together
-with the shortened syntax
-
- 00:02
+with the shortened syntax ``00:02`'
There are some options to which may be necessary, depending on the device
There are some options to which may be necessary, depending on the device
+and guest OS:
+
+* *x-vga=on|off* marks the PCI(e) device as the primary GPU of the VM.
+With this enabled the *vga* configuration option will be ignored.
-* *x-vga=on|off* marks the PCI(e) device the primary GPU of the VM.
-With this enabled the *vga* parameter of the config will be ignored.
* *pcie=on|off* tells {pve} to use a PCIe or PCI port. Some guests/device
* *pcie=on|off* tells {pve} to use a PCIe or PCI port. Some guests/device
-combination require PCIe rather than PCI (only available for q35 machine types).
+combination require PCIe rather than PCI. PCIe is only available for 'q35'
+machine types.
+
* *rombar=on|off* makes the firmware ROM visible for the guest. Default is on.
Some PCI(e) devices need this disabled.
* *rombar=on|off* makes the firmware ROM visible for the guest. Default is on.
Some PCI(e) devices need this disabled.
* *romfile=<path>*, is an optional path to a ROM file for the device to use.
* *romfile=<path>*, is an optional path to a ROM file for the device to use.
-this is a relative path under */usr/share/kvm/*.
+This is a relative path under */usr/share/kvm/*.
+
+Example
++++++++
An example of PCIe passthrough with a GPU set to primary:
----
An example of PCIe passthrough with a GPU set to primary:
----
-qm set VMID -hostpci0 02:00,pcie=on,x-vga=on
+# qm set VMID -hostpci0 02:00,pcie=on,x-vga=on
Other considerations
^^^^^^^^^^^^^^^^^^^^
When passing through a GPU, the best compatibility is reached when using
Other considerations
^^^^^^^^^^^^^^^^^^^^
When passing through a GPU, the best compatibility is reached when using
-q35 as machine type, OVMF instead of SeaBIOS and PCIe instead of PCI.
-Note that if you want to use OVMF for GPU passthrough, the GPU needs
-to have an EFI capable ROM, otherwise use SeaBIOS instead.
+'q35' as machine type, 'OVMF' ('EFI' for VMs) instead of SeaBIOS and PCIe
+instead of PCI. Note that if you want to use 'OVMF' for GPU passthrough, the
+GPU needs to have an EFI capable ROM, otherwise use SeaBIOS instead.
-Another variant of passing through PCI(e) devices, is to use the hardware
-virtualization features of your devices.
+Another variant for passing through PCI(e) devices, is to use the hardware
+virtualization features of your devices, if available.
+
+'SR-IOV' (**S**ingle-**R**oot **I**nput/**O**utput **V**irtualization) enables
+a single device to provide multiple 'VF' (**V**irtual **F**unctions) to the
+system. Each of those 'VF' can be used in a different VM, with full hardware
+features and also better performance and lower latency than software
+virtualized devices.
-SR-IOV (Single-root input/output virtualization) enables a single device
-to provide multiple vf (virtual functions) to the system, so that each
-vf can be used in a different VM, with full hardware features, better
-performance and lower latency than software virtualized devices.
+Currently, the most common use case for this are NICs (**N**etwork
+**I**nterface **C**ard) with SR-IOV support, which can provide multiple VFs per
+physical port. This allows using features such as checksum offloading, etc. to
+be used inside a VM, reducing the (host) CPU overhead.
-The most used devices for this are NICs with SR-IOV which can provide
-multiple vf per physical port, allowing features such as
-checksum offloading, etc. to be used inside a VM, reducing CPU overhead.
Host Configuration
^^^^^^^^^^^^^^^^^^
Host Configuration
^^^^^^^^^^^^^^^^^^
-Generally there are 2 methods for enabling virtual functions on a device.
+Generally, there are two methods for enabling virtual functions on a device.
-In some cases there is an option for the driver module e.g. for some
+* sometimes there is an option for the driver module e.g. for some
-
-which could be put in a file in a .conf file in */etc/modprobe.d/*.
+----
++
+which could be put file with '.conf' ending under */etc/modprobe.d/*.
(Do not forget to update your initramfs after that)
(Do not forget to update your initramfs after that)
Please refer to your driver module documentation for the exact
parameters and options.
Please refer to your driver module documentation for the exact
parameters and options.
-The second (more generic) approach is via the sysfs.
-If a device and driver supports this you can change the number of vfs on
-the fly. For example 4 vfs on device 0000:01:00.0 with:
-
+* The second, more generic, approach is using the `sysfs`.
+If a device and driver supports this you can change the number of VFs on
+the fly. For example, to setup 4 VFs on device 0000:01:00.0 execute:
++
-echo 4 > /sys/bus/pci/devices/0000:01:00.0/sriov_numvfs
+# echo 4 > /sys/bus/pci/devices/0000:01:00.0/sriov_numvfs
-
-To make this change persistent you can use sysfsutils.
-Just install them via
-
-----
-apt install sysfsutils
-----
-
-and configure it via */etc/sysfs.conf* or */etc/sysfs.d/*.
++
+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
+*/etc/sysfs.d/*.
VM Configuration
^^^^^^^^^^^^^^^^
VM Configuration
^^^^^^^^^^^^^^^^
-After creating vfs, you should see them as seperate PCI(e) devices, which
-can be passed through like a normal PCI(e) device.
+After creating VFs, you should see them as separate PCI(e) devices when
+outputting them with `lspci`. Get their ID and pass them through like a
+xref:qm_pci_passthrough_vm_config[normal PCI(e) device].
Other considerations
^^^^^^^^^^^^^^^^^^^^
For this feature, platform support is especially important. It may be necessary
Other considerations
^^^^^^^^^^^^^^^^^^^^
For this feature, platform support is especially important. It may be necessary
-to enable this feature in the BIOS or to use a specific PCI(e) port for it
-to work. In doubt, consult the manual of the platform or contact the vendor.
+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.
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