Re: [libvirt] [PATCH v1 0/3] libxl: nestedhvm support
On Wed, Mar 08, 2017 at 03:07:12PM +0100, Wim Ten Have wrote:
From: Wim ten Have <wim.ten.have(a)oracle.com>
This patch enhances host-passthrough capability to advertise the
required vendor CPU virtualization feature which will be used to
enable 'nestedhvm' in the libxl driver.
For Intel virtualization (VT-x)
..
<cpu mode='host-passthrough'>
<feature policy='require' name='vmx'/>
</cpu>
For AMD virtualization (AMD-V)
..
<cpu mode='host-passthrough'>
<feature policy='require' name='svm'/>
</cpu>
If using host-passthrough or host-model, and the host's CPU includes
vmx or svm, then I would expecte nested-HVM to be enabled, without
needing any extra <feature> flag in the XML. That would match the
semantics used with the QEMU driver.
The only time we would need to use <feature> is if using mode=custom
along with a named CPU model which lacks vmx/svm flags.
BTW, I wonder how hard it would be to wire up the libxl driver to use
the CPU model infrastructure in src/cpu ? It feels a little odd to use
XML <cpu mode='host-passthrough'/> if we're not then making sure it
actually uses host-passthrough when configuring the guest.
Regards,
Daniel
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