[pve-devel] [PATCH pve-docs v8 1/1] update the PCI(e) docs
Dominik Csapak
d.csapak at proxmox.com
Thu Jul 20 10:09:40 CEST 2023
looks mostly fine, some comments inline
On 6/26/23 14:41, Noel Ullreich wrote:
> A little update to the PCI(e) docs with the plan of reworking the PCI
> wiki as well.
>
> Along some minor grammar fixes added:
> * how to check if kernelmodules are being loaded
> * how to check which drivers to blacklist
> * how to add softdeps for module loading
> * where to find kernel params
>
> Signed-off-by: Noel Ullreich <n.ullreich at proxmox.com>
>
> changes from v1:
> * fixed spelling mistakes
> * reduced code snippets of how to check iommu groupings to one
> * moved where to find kernel params to kernel cmdline section
> * removed wrong info on display output. will add correct info to
> Examples-Wiki
> * changed module names to variable-names, so that people can't
> blindly copy-paste.
> * restructured commit message ;)
>
> changes from v2:
> * while moving where to find the kernel params to the kernel
> cmdline section, I forgot to remove it from the pci(e) section
> * fixed typo in the link to the kernel param section
>
> changes from v3:
> * Some restructuring of the layout as well as moving parts of the
> PCI examples wiki to the docs here. This should lead to well-
> structured, concise docs that are independent from the PCI wiki.
> * found some more minor grammar errors
> * found a spelling mistake in qm.adoc
>
> changes from v4:
> * formatted the git message wrong again :/
>
> changes from v5:
> * fixed links to wiki
> * moved where to find kernel params to end of its chapter
> * the `vfio_virqfd` does not need to be loaded anymore with kernel 6.2
>
> changes from v6: the public wiki was updated -> fixed the links
>
> changes from v7: Forum user Leesteken noted that for Intel cpus
> IOMMU is not automatically activated anymore.
> https://forum.proxmox.com/threads/fix-pci-passthrough-documentation.122521/post-566926
> Thanks Leesteken :)
>
> Signed-off-by: Noel Ullreich <n.ullreich at proxmox.com>
> ---
> qm-pci-passthrough.adoc | 160 ++++++++++++++++++++++++++++++----------
> qm.adoc | 2 +-
> system-booting.adoc | 8 ++
> 3 files changed, 132 insertions(+), 38 deletions(-)
>
> diff --git a/qm-pci-passthrough.adoc b/qm-pci-passthrough.adoc
> index b90a0b9..2ff9b7e 100644
> --- a/qm-pci-passthrough.adoc
> +++ b/qm-pci-passthrough.adoc
> @@ -13,19 +13,27 @@ features (e.g., offloading).
> 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.
>
> +Note that, while PCI passthrough is available for i440fx and q35 machines, PCIe
> +passthrough is only available on q35 machines. This does not mean that
> +PCIe capable devices that are passed through as PCI devices will only run at
> +PCI speeds. Passing through devices as PCIe just sets a flag for the guest to
> +tell it that the device is a PCIe device instead of a "really fast legacy PCI
> +device". Some guest applications benefit from this.
> +
> General Requirements
> ~~~~~~~~~~~~~~~~~~~~
>
> -Since passthrough is a feature which also needs hardware support, there are
> -some requirements to check and preparations to be done to make it work.
> -
> +Since passthrough is performed on real hardware, it needs to fulfill some
> +requirements. A brief overview of these requirements is given below, for more
> +information on specific devices, see
> +https://pve.proxmox.com/wiki/PCI_Passthrough[PCI Passthrough Examples].
>
> Hardware
> ^^^^^^^^
> Your hardware needs to support `IOMMU` (*I*/*O* **M**emory **M**anagement
> **U**nit) interrupt remapping, this includes the CPU and the mainboard.
>
> -Generally, Intel systems with VT-d, and AMD systems with AMD-Vi support this.
> +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.
>
> @@ -35,6 +43,17 @@ hardware, but even then, many modern system can support this.
> Please refer to your hardware vendor to check if they support this feature
> under Linux for your specific setup.
>
> +Determining PCI Card Address
> +^^^^^^^^^^^^^^^^^^^^^^^^^^^^
> +
> +The easiest way is to use the GUI to add a device of type "Host PCI" in the VM's
> +hardware tab. Alternatively, you can use the command line.
> +
> +You can locate your card using
> +
> +----
> + lspci
> +----
>
> Configuration
> ^^^^^^^^^^^^^
> @@ -44,13 +63,12 @@ some configuration to enable PCI(e) passthrough.
>
> .IOMMU
>
> -First, you have to enable IOMMU support in your BIOS/UEFI. Usually the
> -corresponding setting is called `IOMMU` or `VT-d`,but you should find the exact
> +First, you will have to enable IOMMU support in your BIOS/UEFI. Usually the
> +corresponding setting is called `IOMMU` or `VT-d`, but you should find the exact
> option name in the manual of your motherboard.
>
> -For Intel CPUs, you may also need to enable the IOMMU on the
> -xref:sysboot_edit_kernel_cmdline[kernel command line] for older (pre-5.15)
> -kernels by adding:
> +For Intel CPUs, you also need to enable the IOMMU on the
> +xref:sysboot_edit_kernel_cmdline[kernel command line] kernels by adding:
>
> ----
> intel_iommu=on
> @@ -75,13 +93,15 @@ to the xref:sysboot_edit_kernel_cmdline[kernel commandline].
> .Kernel Modules
>
> You have to make sure the following modules are loaded. This can be achieved by
> -adding them to `'/etc/modules''
> +adding them to `'/etc/modules''. In kernels newer than 6.2 ({pve} 8 and onward)
> +the 'vfio_virqfd' module is part of the 'vfio' module, therefore loading
> +'vfio_virqfd' in {pve} 8 and newer is not necessary.
>
> ----
> vfio
> vfio_iommu_type1
> vfio_pci
> - vfio_virqfd
> + vfio_virqfd #not needed if on kernel 6.2 or newer
> ----
i'd add some comment (does such a thing exists in asciidoc?) or something
so that we can remove that part with e.g. pve 9.x
since thats only relevant as long as we're supporting 7.x
if it's not possible to add a comment in asciidoc, then just leave it as is
>
> [[qm_pci_passthrough_update_initramfs]]
> @@ -92,6 +112,14 @@ After changing anything modules related, you need to refresh your
> # update-initramfs -u -k all
> ----
>
> +To check if the modules are being loaded, the output of
> +
> +----
> +# lsmod | grep vfio
> +----
> +
> +should include the four modules from above.
> +
> .Finish Configuration
>
> Finally reboot to bring the changes into effect and check that it is indeed
> @@ -104,11 +132,16 @@ enabled.
> should display that `IOMMU`, `Directed I/O` or `Interrupt Remapping` is
> enabled, depending on hardware and kernel the exact message can vary.
>
> +For notes on how to troubleshoot or verify if IOMMU is working as intended, please
> +see the https://pve.proxmox.com/wiki/PCI_Passthrough#Verifying_IOMMU_parameters[Verifying IOMMU Parameters]
> +section in our wiki.
> +
> It is also important that the device(s) you want to pass through
> -are in a *separate* `IOMMU` group. This can be checked with:
> +are in a *separate* `IOMMU` group. This can be checked with a call to the {pve}
> +API:
>
> ----
> -# find /sys/kernel/iommu_groups/ -type l
> +# pvesh get /nodes/{nodename}/hardware/pci --pci-class-blacklist ""
> ----
>
> It is okay if the device is in an `IOMMU` group together with its functions
> @@ -159,8 +192,8 @@ PCI(e) card, for example a GPU or a network card.
> Host Configuration
> ^^^^^^^^^^^^^^^^^^
>
> -In this case, the host must not use the card. There are two methods to achieve
> -this:
> +{pve} tries to automatically make the PCI(e) device unavailable for the host.
> +However, if this doesn't work, there are two things that can be done:
>
> * pass the device IDs to the options of the 'vfio-pci' modules by adding
> +
> @@ -175,7 +208,7 @@ the vendor and device IDs obtained by:
> # lspci -nn
> ----
>
> -* blacklist the driver completely on the host, ensuring that it is free to bind
> +* blacklist the driver on the host completely, ensuring that it is free to bind
> for passthrough, with
> +
> ----
> @@ -183,11 +216,49 @@ for passthrough, with
> ----
> +
> in a .conf file in */etc/modprobe.d/*.
> ++
> +To find the drivername, execute
> ++
> +----
> +# lspci -k
> +----
> ++
> +for example:
> ++
> +----
> +# lspci -k | grep -A 3 "VGA"
> +----
> ++
> +will output something similar to
> ++
> +----
> +01:00.0 VGA compatible controller: NVIDIA Corporation GP108 [GeForce GT 1030] (rev a1)
> + Subsystem: Micro-Star International Co., Ltd. [MSI] GP108 [GeForce GT 1030]
> + Kernel driver in use: <some-module>
> + Kernel modules: <some-module>
> +----
> ++
> +Now we can blacklist the drivers by writing them into a .conf file:
> ++
> +----
> +echo "blacklist <some-module>" >> /etc/modprobe.d/blacklist.conf
> +----
>
> For both methods you need to
> xref:qm_pci_passthrough_update_initramfs[update the `initramfs`] again and
> reboot after that.
>
> +Should this not work, you might need to set a soft dependency to load the gpu
> +modules before loading 'vfio-pci'. This can be done with the 'softdep' flag, see
> +also the manpages on 'modprobe.d' for more information.
> +
> +For example, if you are using drivers named <some-module>:
> +
> +----
> +# echo "softdep <some-module> pre: vfio-pci" >> /etc/modprobe.d/<some-module>.conf
> +----
> +
> +
> .Verify Configuration
>
> To check if your changes were successful, you can use
> @@ -208,13 +279,42 @@ passthrough.
> [[qm_pci_passthrough_vm_config]]
> VM Configuration
> ^^^^^^^^^^^^^^^^
> -To pass through the device you need to set the *hostpciX* option in the VM
> +When passing through a GPU, the best compatibility is reached when using
> +'q35' as machine type, 'OVMF' ('UEFI' 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 UEFI capable ROM, otherwise use SeaBIOS instead. To check if
> +the ROM is UEFI capable, see the
> +https://pve.proxmox.com/wiki/PCI_Passthrough#How_to_know_if_a_graphics_card_is_UEFI_.28OVMF.29_compatible[PCI Passthrough Examples]
> +wiki.
> +
> +Furthermore, using OVMF, disabling vga arbitration may be possible, reducing the
> +amount of legacy code needed to be run during boot. To disable vga arbitration:
> +
> +----
> + echo "options vfio-pci ids=<vendor-id>,<device-id> disable_vga=1" > /etc/modprobe.d/vfio.conf
> +----
> +
> +replacing the <vendor-id> and <device-id> with the ones obtained from
> +
> +----
> +# lspci -nn
> +----
> +
> +PCI devices can be added in the web interface in the hardware section of the VM.
> +Alternatively, you can use the command line; set the *hostpciX* option in the VM
> configuration, for example by executing:
>
> ----
> # qm set VMID -hostpci0 00:02.0
> ----
>
> +or by adding a line to the VM configuration file:
> +
> +----
> + hostpci0: 00:02.0
> +----
> +
> +
> 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`'.
> This is equivalent with checking the ``All Functions`' checkbox in the
> @@ -262,21 +362,17 @@ For example:
> # qm set VMID -hostpci0 02:00,device-id=0x10f6,sub-vendor-id=0x0000
> ----
>
> -
> -Other considerations
> -^^^^^^^^^^^^^^^^^^^^
> -
> -When passing through a GPU, the best compatibility is reached when using
> -'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.
> -
> SR-IOV
> ~~~~~~
>
> -Another variant for passing through PCI(e) devices, is to use the hardware
> +Another variant for passing through PCI(e) devices is to use the hardware
> virtualization features of your devices, if available.
>
> +{{Note | To use SR-IOV, platform support is especially important. It may be necessary
> +to enable this feature in the BIOS/UEFI 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.}}
this syntax does not work here with the html nor the pdf renderer, maybe
some bad copy&paste ?
> +
> '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
> @@ -288,7 +384,6 @@ Currently, the most common use case for this are NICs (**N**etwork
> physical port. This allows using features such as checksum offloading, etc. to
> be used inside a VM, reducing the (host) CPU overhead.
>
> -
> Host Configuration
> ^^^^^^^^^^^^^^^^^^
>
> @@ -326,14 +421,6 @@ 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
> -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)
> ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
>
> @@ -346,7 +433,6 @@ 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
> ^^^^^^^^^^^^^^^^^^
>
> diff --git a/qm.adoc b/qm.adoc
> index b3c3034..ed804e2 100644
> --- a/qm.adoc
> +++ b/qm.adoc
> @@ -139,7 +139,7 @@ snapshots) more intelligently.
> {pve} allows to boot VMs with different firmware and machine types, namely
> xref:qm_bios_and_uefi[SeaBIOS and OVMF]. In most cases you want to switch from
> the default SeaBIOS to OVMF only if you plan to use
> -xref:qm_pci_passthrough[PCIe pass through]. A VMs 'Machine Type' defines the
> +xref:qm_pci_passthrough[PCIe passthrough]. A VMs 'Machine Type' defines the
> hardware layout of the VM's virtual motherboard. You can choose between the
> default 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]
> diff --git a/system-booting.adoc b/system-booting.adoc
> index 30621a6..e2e9214 100644
> --- a/system-booting.adoc
> +++ b/system-booting.adoc
> @@ -288,6 +288,14 @@ The kernel commandline needs to be placed as one line in `/etc/kernel/cmdline`.
> To apply your changes, run `proxmox-boot-tool refresh`, which sets it as the
> `option` line for all config files in `loader/entries/proxmox-*.conf`.
>
> +A complete list of kernel parameters can be found at
> +'https://www.kernel.org/doc/html/v<YOUR-KERNEL-VERSION>/admin-guide/kernel-parameters.html'.
> +replace <YOUR-KERNEL-VERSION> with the major.minor version (e.g. 5.15). You can
> +find your kernel version by running
> +
> +----
> +# uname -r
> +----
>
> [[sysboot_kernel_pin]]
> Override the Kernel-Version for next Boot
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