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Description of problem:
Hyper-V 2016 fails to boot on Skylake+ CPU models because they lack 'xsaves'/'vmx-xsaves' features.
qemu-kvm added support in:
https://bugzilla.redhat.com/show_bug.cgi?id=1942914.
Libvirt also needs to add support for for 'xsaves'/'vmx-saves' on Skylake+ CPU models.
libvirt CPU models are immutable and may differ from their qemu counterparts.
Please try to enable the missing features explicitly in your domain XML as a work around like this:
<cpu>
<model>Skylake</model>
<feature policy='require' name='xsaves'/>
<feature policy='require' name='vmx-xsaves'/>
</cpu>
> <cpu>
> <model>Skylake</model>
> <feature policy='require' name='xsaves'/>
> <feature policy='require' name='vmx-xsaves'/>
> </cpu>
Two things:
- vmx-xsaves is unknown to libvirt so you can't ask for it via XML
- you don't need to add any of these features to the XML unless you need
libvirt to check the host supports xsaves
In other words, using just Skylake should enable these features as long as
QEMU selects the newest version of Skylake for a chosen machine type. If it
doesn't do so, this BZ remains TestOnly, but it would depend on bug 1856522
and bug 1727122.
I have tested on libvirt-daemon-7.5.0-1.module+el8.5.0+11664+59f87560.x86_64, libvirt not support vmx-xsaves feature.
# grep -rin "xsaves" /usr/share/libvirt/cpu_map/
/usr/share/libvirt/cpu_map/x86_EPYC-Milan.xml:90: <feature name='xsaves'/>
/usr/share/libvirt/cpu_map/x86_features.xml:383: <feature name='xsaves' migratable='no'>
# grep -rin "vmx-xsaves" /usr/share/libvirt/cpu_map/
If you try to start a guest which enable vmx-xsaves feature, you will get an error like this:
# virsh start vm1
error: Failed to start domain 'vm1'
error: unsupported configuration: unknown CPU feature: vmx-xsaves
This bug was initially requested as a feature for Red Hat Virtualization (RHV)
RHV is in Maintenance phase and will be End of Life in 2024.
We are unlikely to fix this BZ, so CLOSING this bug as WONTFIX.