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[Xen-devel] Re: pv_ops dom0 kernel and VT cpu extensions

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Subject: [Xen-devel] Re: pv_ops dom0 kernel and VT cpu extensions
From: Christian Tramnitz <chris.ace@xxxxxxx>
Date: Tue, 29 Dec 2009 10:53:38 +0100
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Gerry Reno wrote:
I compiled a pv_ops dom0 kernel from Jeremy's latest git tree and upgraded Xen to 3.4.1 following one of Boris' blog entries. From the Xen perspective everything seems to work as expected. But, I want to be able to run both Xen and KVM existing guests in a single cloud on a farm of VT-enabled machines. So after booting into the new pv_ops dom0 kernel as a test I tried starting one of my KVM guests. It ran extremely slow so I knew immediately that it wasnt' using the VT acceleration. I then looked at /proc/cpuinfo and saw that the VT cpu flag (svm on this machine) was not there. The machine has a VT processor and hardware virtualization is enabled in the BIOS and I rebooted to check with a regular kernel and it of course the guest runs with VT acceleration there. My question is how can I get pv_ops dom0 kernel or Xen 3.4.1 to pass the cpu VT flags through so that existing KVM guests will run with cpu VT acceleration at full speed?

You need to start the pvops kernel on bare metal (without Xen) to make use of VT. dom0 is already a (privileged) guest (of Xen), so the hardware assisted virtualization interface is simply not accessible at this point anymore...

Best regards,

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