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I just recognized, that 2 of my 10 VMs in XenCenter have a slightly different properties window. In these two VMs I cannot set OS boot parameters, because in the window I can only set the boot order. So I have attached two screenshots from the different windows. Are these different types of VMs and how can I change them?

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PS: The 2 VMs with this missing field also do not allow me to past something in the virtual console.

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up vote 4 down vote accepted

The first VM is running in PVHVM mode, so QEMU is working with Xen to virtualize the hardware behind the VM. This mode is for OS that does not support Xen paravirtualization in general, like Windows and FreeBSD.

The second one is from a VM running in PV mode. In this mode, everything is paravirtualized. So there's no emulated BIOS. The booting process is defined by pygrub and this screen shows the options available in this mode. Commonly Linux VM's and 32 bits FreeBSD runs in this mode.

You can change to PVHVM and PV if supported by the guest OS.

As today appears to be a good ideia to run everything in PVHVM, even the hosts with full paravirtualization support. You can check some benchmarks over here:

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Thank you. Just FYI: To test if a VM is HVM or not: xe vm-param-get uuid=<VM uuid> param-name=HVM-boot-policy If it is set to “BIOS order” (or other non-empty string?) then HVM is enabled. source: – Dirk Aug 3 '14 at 17:21
Yep... I know. I already have two scripts to do PVHVM to PV and PV to PVHVM conversions. :) – Vinícius Ferrão Aug 3 '14 at 17:29

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