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Descriptionjblume@redhat.com
2016-03-02 14:17:42 UTC
Description of problem:
When trying to set up a virtual machine on a CPU E7-8870 (Westmere) it shows that the invtsc feature cannot be used inside the domain XML. According to the output of
# virsh capabilities
this should be the case.
Version-Release number of selected component (if applicable):
- kernel-3.10.0-327.10.1.el7.x86_64
- libvirt-1.2.17-13.el7_2.3
How reproducible:
Set up a RHEL7.2 VM on an RHEL7.2 hypervisor
Steps to Reproduce:
1. Install the VM
2. Start it with <cpu mode='host-model'> inside XML
3. The flag nonstop_tsc isn't present in /proc/cpuinfo as invtsc is missing
4. Add to XML: <feature policy='require' name='invtsc'/>
5. Try to start the VM with virsh start <domain>
Actual results:
Error message:
error: Failed to start domain ls3059v1
error: unsupported configuration: host doesn't support invariant TSC
Expected results:
VM starts
Additional info:
This appears to also be the case for Sandy Bridge. I have the same setup - RHEL 7.2 host, virsh capabilities does show invtsc, I added to my xml as <feature policy='require' name='invtsc'/> and get no errors at define or guest start up.
I do not see invtsc in /proc/cpuinfo for either the host or guest. The qemu process does not have it either.
Dave
The RHEL7 hypervisor (qemu-kvm from the qemu-kvm package) does not support invtsc.
The support is only in the RHEV hypervisor (qemu-kvm from the qemu-kvm-rhev package). I suggest closing this as NOTABUG.
The feature shows in /proc/cpuinfo as nonstop_tsc, not invtsc.
Comment 7jblume@redhat.com
2016-03-22 17:58:06 UTC
Thanks to Jan Tomko we now have a reliable status about qemu-kvm in RHEL7.2.
What we checked out now:
1. Subscribed the system to the RHEV channel
2. Installed the quemu-kvm-rhev package which updated qemu-kvm
3. Switched the guest off and on again
4. The desired CPU flags {constant,nonstop}_tsc are now visible within the guest.
So we can close this bug for now. Thank you all.