Feature #6683


Support PV vm's install

Added by George Lucan almost 10 years ago. Updated over 8 years ago.

Fixed in Releases:
Found in Releases:



It would be nice to be able to install pv vm's.
Before answering "That is not a xenserver supported feature" I will explain.

At the moment the plugin sets HVM boot to the vm on creation.
It is possible to convert it to PV via changeing the HVM_BOOT and PV_BOOT attributed of the vm(like xenserver does when you install from template and start the vm in recovery mode)

As I see it this can be made possible by using the before_provision and after_build hooks(they will change to hvmboot before provision and change it to pvboot after build completed)

The motivation behind this request is the performance differences between the 2 types of boot.

Thank you

Actions #1

Updated by Pujan Shah over 9 years ago

This is manually achivable and it would be great if this can be automated via plugin

Actions #2

Updated by Ben Bettridge about 9 years ago

You might want to have a look at PVHVM machines and the performance increases found there. It's worth noting that PV is not uniformly faster/better than PVHVM, it depends on the version of Xen, Linux Kernel and exactly what the VM is being used for.

I have hacked support for this in to our current internal codebase but it bootstraps an actual PV install using pygrub instead of converting from HVM afterwards. In the end supporting different versions of pygrub became a nightmare and now we run everything as PVHVM.

Actions #3

Updated by George Lucan about 9 years ago


You are right that things have changed since I opened this feature request.

I will explain:
We used RHEL 6 on most machines. The supported way (that Citrix recommended) was installing by template(that was PV). Also we had a lot of issues(and there were a lot of bugs in RHEL 6 with memory management and a PVHVM guest, the ballooning driver was badly broken and refused to release memory when xenserver asked). RHEL 6 in PV modes had no issues.

RHEL 7 changed the game and now the recommended install is PVHVM.

At this point in time it is more like a nice to have.


Actions #4

Updated by Anonymous over 8 years ago

  • Status changed from New to Rejected

Closing this on the "That is not a xenserver supported feature" card as it's next to impossible to implement this in a clean way when it's not supported by Xen itself and exposed via API, usable by fog.


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