Bug 1309102 - CPU stepping value different in the same VM when started on different hosts, even if baseline is set via libvirt or RHEV
Summary: CPU stepping value different in the same VM when started on different hosts, ...
Keywords:
Status: CLOSED INSUFFICIENT_DATA
Alias: None
Product: Red Hat Enterprise Linux 7
Classification: Red Hat
Component: qemu-kvm-rhev
Version: 7.2
Hardware: x86_64
OS: Linux
medium
low
Target Milestone: rc
: ---
Assignee: Eduardo Habkost
QA Contact: Virtualization Bugs
URL:
Whiteboard:
Depends On:
Blocks:
TreeView+ depends on / blocked
 
Reported: 2016-02-16 20:29 UTC by Dan Yasny
Modified: 2019-10-10 11:13 UTC (History)
14 users (show)

Fixed In Version:
Doc Type: Bug Fix
Doc Text:
Clone Of:
Environment:
Last Closed: 2016-04-28 18:50:12 UTC
Target Upstream Version:


Attachments (Terms of Use)

Description Dan Yasny 2016-02-16 20:29:05 UTC
Description of problem:
When starting a VM on different hosts, inside the VM, the CPU stepping value is different

This can interfere with some software that expects the hardware profile to remain static.

Version-Release number of selected component (if applicable):
[root@hv01 ~]# rpm -qa |grep qemu
qemu-img-rhev-2.1.2-23.el7_1.9.x86_64
qemu-kvm-rhev-2.1.2-23.el7_1.9.x86_64
libvirt-daemon-driver-qemu-1.2.8-16.el7_1.4.x86_64
qemu-kvm-common-rhev-2.1.2-23.el7_1.9.x86_64
qemu-kvm-tools-rhev-2.1.2-23.el7_1.9.x86_64
ipxe-roms-qemu-20130517-6.gitc4bce43.el7.noarch


How reproducible:
always

Steps to Reproduce:
1. start a Windows VM on one host
2. get a CPU-z dump
3. restart the VM on a different host with different CPU (both hosts set to same baseline CPU model, e.g. nehalem)
4. check the CPU-z dump again

Actual results:
different stepping values visible

Expected results:
should be exactly the same

Additional info:

This is a minor issue so far, opening as per request from the virt team. 

Support ticket should be #01584470

Comment 8 Eduardo Habkost 2016-02-17 20:36:07 UTC
(In reply to Dan Yasny from comment #0)
> Steps to Reproduce:
> 1. start a Windows VM on one host
> 2. get a CPU-z dump
> 3. restart the VM on a different host with different CPU (both hosts set to
> same baseline CPU model, e.g. nehalem)
> 4. check the CPU-z dump again
> 
> Actual results:
> different stepping values visible

This description does not match what we see on the CPU-Z dumps. The CPUID stepping field is kept exactly the same. The only CPUID change seen on the two logs is at CPUID[0x80000008].


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