Configuring the compute cluster for PCI passthrough

To enable PCI passthrough for the compute cluster, you need to create a configuration file in the YAML format and use it to reconfigure the compute cluster.

Below is an example of pci-passthrough.yaml:

- node_id: c3b2321a-7c12-8456-42ce-8005ff937e12
  devices:
    - device_type: sriov
      device: enp2s0
      physical_network: sriovnet
      num_vfs: 8
    - device_type: generic
      device: 1b36:0100
      alias: gpu

In this configuration file:

node_id is the identifier of a compute node that hosts PCI devices
device_type can be sriov for a network adapter or generic for a graphics card
device is the device name for a network adapter or the VID and PID for a graphics card
physical_network is an arbitrary name that will be used as an alias for a network adapter
alias is an arbitrary name that will be used as an alias for a graphics card
num_vfs is the number of virtual functions to create for a PCI device with the sriov device type

The maximum number of virtual functions supported by a PCI device is specified in the /sys/class/net/<device_name>/device/sriov_totalvfs file. For example:
```
# cat /sys/class/net/enp2s0/device/sriov_totalvfs
63
```

Now, you can pass this configuration file to the vinfra service compute set command. For example:

# vinfra service compute set --pci-passthrough-config pci-passthrough.yaml
+---------+--------------------------------------+
| Field   | Value                                |
+---------+--------------------------------------+
| task_id | 624916c6-617b-4687-b52c-b348e1f4892a |
+---------+--------------------------------------+

If the reconfiguration fails with the following error in /var/log/vstorage-ui-backend/ansible.log:

2021-09-23 16:42:59,796 p=32130 u=vstoradmin | fatal: [32c8461b-92ec-48c3-ae02-
4d12194acd02]: FAILED! => {"changed": true, "cmd": "echo 4 > /sys/class/net/
enp103s0f1/device/sriov_numvfs", "delta": "0:00:00.127417", "end": "2021-09-23 
19:42:59.784281", "msg": "non-zero return code", "rc": 1, "start": "2021-09-23 
19:42:59.656864", "stderr": "/bin/sh: line 0: echo: write error: Cannot allocate 
memory", "stderr_lines": ["/bin/sh: line 0: echo: write error: Cannot allocate memory"], 
"stdout": "", "stdout_lines": []}

In this case, run the the pci-helper.py script, and reboot the node:

# /usr/libexec/vstorage-ui-agent/bin/pci-helper.py enable-iommu --pci-realloc
# reboot

When the node is up again, repeat the vinfra service compute set command.

After the compute cluster is successfully reconfigured, you can proceed to creating virtual machines.