Virtual Hardware Platform: changes missed from prev commit

Signed-off-by: Thomas Sanders <[email protected]>

Author: thomassa

xen-api/futures/virt-hw-platform-vn/virt-hw-platform-vn.md

@@ -14,8 +14,8 @@ We want a clean way to ensure that xapi only tries to run a guest VM on a host t
 
 ### Suggested design
 
-* In the datamodel, VM has a new integer field "virt_hw_vn" which defaults to zero.
-* In the datamodel, Host has a corresponding new integer-list field "virt_hw_vns" which defaults to list containing a single zero element (i.e. `[0]` or `[0L]` in OCaml notation). The zero represents the implicit version supported by older hosts that lack the code to handle the Virtual Hardware Platform Version concept.
+* In the datamodel, VM has a new integer field "hardware_platform_version" which defaults to zero.
+* In the datamodel, Host has a corresponding new integer-list field "virtual_hardware_platform_versions" which defaults to list containing a single zero element (i.e. `[0]` or `[0L]` in OCaml notation). The zero represents the implicit version supported by older hosts that lack the code to handle the Virtual Hardware Platform Version concept.
 * When a host boots it populates its own entry from a hardcoded value, currently `[0; 1]` i.e. a list containing the two integer elements `0` and `1`. (Alternatively this could come from a config file.)
   * If this new version-handling functionality is introduced in a hotfix, at some point the pool master will have the new functionality while at least one slave does not. An old slave-host that does not yet have software to handle this feature will not set its DB entry, which will therefore remain as `[0]` (maintained in the DB by the master).
 * The existing test for whether a VM can run on (or migrate to) a host must include a check that the VM's virtual hardware platform version is in the host's list of supported versions.
@@ -31,7 +31,7 @@ Version 1 denotes support for a certain feature:
 
 If the PCI device is removed, the guest OS will fail to boot. A VM using this feature must not be migrated to or started on a XenServer that lacks support for the feature.
 
-Therefore at VM start, we can look at whether this feature is being used; if it is, we should raise the VM's Virtual Hardware Platform Version to 1 if it is less than 1.
+Therefore at VM start, we can look at whether this feature is being used; if it is, then if the VM's Virtual Hardware Platform Version is less than 1 we should raise it to 1.
 
 ### Limitation
 Consider a VM that requires version 1 or higher. Suppose it is exported, then imported into an old host that does not support this feature. Then the host will not check the versions but will attempt to run the VM, which will then have difficulties.