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CloudStack users wish to have the functionality to add “extra configuration” metadata to a user VM during deployment in a manner that is similar across the 3 major supported hypervisors. This data could be anything ranging from instructions to install hypervisor specific required tools and drivers in each VM that is deployed from a template which does not have these tools installed. To simplify the implementation, the user will pass this additional configuration as URL encoded string that will be decoded and parsed for each hypervisor type. These additional metadata must be included in the VM instance definition.

Any additional configuration setting/command needs to be first included into the list of allowed settings by the Root Admin through a configurable global configuration.  No command/setting is allowed by default.

• KVM

The primary configuration file for KVM host guest instances is a domain XML. The additional configuration for KVM should be provided in XML format in a URL encoded string which will be parsed and append to the KVM instance XML configuration file builder.

A configurable global config 'allow.additional.vm.configuration.list.kvm' is available for Root admin to specify a list options that are allowed with this feature. with KVM No option is allowed by default. 

Example: the following metadata can be passed to enable hugepages on KVM hosts., with 'memoryBacking' included in the list of allowed setting/configuration

<memoryBacking>
       <hugepages/>
</memoryBacking>

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Another Example: the following examples allows user to add EHCI controller to VM, also with the 'controller' element/tag included in the list of allowed settings/configuration

<controller type='usb' index='1' model='ehci'></controller>

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%3Ccontroller%20type%3D%27usb%27%20index%3D%271%27%20model%3D%27ehci%27%3E%3C%2Fcontroller%3E

A configurable global config 'allow.additional.vm.configuration.list.kvm' is available for Root admin to specify a list options that are allowed with this feature.

• Default values are; 'memoryBacking'

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• XenServer

xe vm-param-set manual page

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Simple key=value pair configurations, e.g PV-args=hvc0, is-a-template=true. Any of these settings will override an existing setting with the new value from the user.

A configurable global config 'allow.additional.vm.configuration.list.xenserver' is available for Root admin to specify a list of 'vm-param-set' options that are allowed with this feature. No configuration is allowed by default.

• • is-a-template, 

  • memory-static-max, 

  • memory-dynamic-max, 

  • memory-dynamic-min, 

  • memory-static-min, 

  • VCPUs-max, 

  • VCPUs-at-startup, 

  • HVM-boot-policy, 

  • order,

  • shutdown-delay, Long

  • start-delay, Long

  • ha-restart-priority, 

  • PV-bootloader-args, 

  • PV-bootloader, 

  • PV-legacy-args, 

  • PV-args, 

  • PV-ramdisk, 

  • PV-kernel, 

  • HVM-shadow-multiplier,

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Example: Following commands are used to convert a VM from HVM to PV;, also admin needs to include HVM-boot-policy, PV-bootloader and PV-args for the configuration below to be allowed.

HVM-boot-policy=
PV-bootloader=pygrub
PV-args=hvc0

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And verify that they have been correctly set.

• A configurable global config 'allow.additional.vm.configuration.list.xenserver' is available for Root admin to specify a list of 'vm-param-set' options that are disallowed with this feature.

  • Default values are; 'HVM-boot-policy, PV-bootloader, PV-args'

The algorithm for XenServer does the following checks;

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Similar for this hypervisor, the primary configuration file of the guest VM is built by CloudStack, therefor, the additional metadata will also be parsed and append to the VMX file builder.

A configurable global config 'allow.additional.vm.configuration.list.vmware' is available for Root admin to specify a list options that are allowed with this feature.

Example: the following is an example to set Hyper-V to run on ESXi, with 'hypervisor.cpuid.v0' included on the list of allowed settings/configuration keys.

hypervisor.cpuid.v0=FALSE

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• find / -name *.vmx
• cat <vmx file path> | grep \w ‘extra config’

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The configuration passed is parsed as key/value pair and every key is validated against against the allowed list of commands set by Root admin. An Exception is thrown if an invalid key is found.

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