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Bug 1341492

Summary: QEMU on POWER does not support the PowerISA 2.07 compatibility mode
Product: Red Hat Enterprise Linux 7 Reporter: Thomas Huth <thuth>
Component: qemu-kvm-rhevAssignee: Thomas Huth <thuth>
Status: CLOSED ERRATA QA Contact: Virtualization Bugs <virt-bugs>
Severity: medium Docs Contact:
Priority: unspecified    
Version: 7.3CC: bugproxy, dgibson, gduarte, hannsj_uhl, jstancek, mrezanin, qzhang, sbest, virt-maint, xuhan, zhengtli
Target Milestone: rc   
Target Release: 7.3   
Hardware: ppc64le   
OS: Linux   
Whiteboard:
Fixed In Version: qemu-kvm-rhev-2.6.0-8.el7 Doc Type: If docs needed, set a value
Doc Text:
Story Points: ---
Clone Of: Environment:
Last Closed: 2016-11-07 21:13:15 UTC Type: Bug
Regression: --- Mount Type: ---
Documentation: --- CRM:
Verified Versions: Category: ---
oVirt Team: --- RHEL 7.3 requirements from Atomic Host:
Cloudforms Team: --- Target Upstream Version:
Embargoed:
Bug Depends On: 1340445    
Bug Blocks: 1359843    

Description Thomas Huth 2016-06-01 07:58:06 UTC
Description of problem:
If a RHEL KVM guest is currently run on a POWER8NVL host, it ends up in POWER7 compatibility mode (according to /proc/cpuinfo). This happens because the guests currently do not announce support for POWER8NVL directly (see BZ 1340445 for details), and because QEMU does not support the PowerISA 2.07 compatibility mode in the "ibm,client-architecture-support" firmware call. So the guests end up in PowerISA 2.06 mode, which equals to POWER7.
While BZ 1340445 tracks the modifications to the guest kernel, this ticket here is used to track the fixes for QEMU to properly provide the PowerISA 2.07 compatibility mode for guests, too.

Version-Release number of selected component (if applicable):
qemu-kvm-rhev-2.6.0-4.el7.ppc64le

How reproducible:
100%

Steps to Reproduce:
1. Boot a RHEL 7.2 on a POWER8NVL KVM host
2. Check /proc/cpuinfo.

Actual results:
If /proc/cpuinfo contains POWER7, it is the wrong setting.

Expected results:
/proc/cpuinfo should say something about POWER8 instead.

Comment 2 Miroslav Rezanina 2016-06-21 07:03:55 UTC
Fix included in qemu-kvm-rhev-2.6.0-8.el7

Comment 4 Zhengtong 2016-07-06 04:30:10 UTC
Reproduced the problem with the set up as follows:
---------------------------------------------------
Host: garrison 
cpu: POWER8NVL

on host check cpu type:
[root@ibm-p8-garrison-01 ~]# cat /proc/cpuinfo 
processor	: 0
cpu		: POWER8NVL (raw), altivec supported
clock		: 4023.000000MHz
revision	: 1.0 (pvr 004c 0100)

processor	: 8
cpu		: POWER8NVL (raw), altivec supported
clock		: 4023.000000MHz
revision	: 1.0 (pvr 004c 0100)
...

qemu-kvm-rhev-2.6.0-7.el7
guest: ppc64 and ppc64le
---------------------------------------------------

Boot up the ppc64 guest , and check the cpu info
[root@dhcp71-27 ~]# cat /proc/cpuinfo 
processor	: 0
cpu		: POWER7 (architected), altivec supported
clock		: 3259.000000MHz
revision	: 1.0 (pvr 004c 0100)

processor	: 1
cpu		: POWER7 (architected), altivec supported
clock		: 3259.000000MHz
revision	: 1.0 (pvr 004c 0100)
...

It is POWER7 cpu.

Boot up the ppc64le guest ,and check the cpu info
 [root@dhcp112-244 ~]# cat /proc/cpuinfo 
processor	: 0
cpu		: POWER7 (architected), altivec supported
clock		: 3259.000000MHz
revision	: 1.0 (pvr 004c 0100)

processor	: 1
cpu		: POWER7 (architected), altivec supported
clock		: 3259.000000MHz
revision	: 1.0 (pvr 004c 0100)
...

It is POWER7 cpu

----------------------------------------------------------
Update the qemu-kvm version to qemu-kvm-rhev-2.6.0-8.el7

start ppc64 guest again. check the cpu info:
[root@dhcp71-27 ~]# cat /proc/cpuinfo 
processor	: 0
cpu		: POWER8 (architected), altivec supported
clock		: 3259.000000MHz
revision	: 1.0 (pvr 004c 0100)

processor	: 1
cpu		: POWER8 (architected), altivec supported
clock		: 3259.000000MHz
revision	: 1.0 (pvr 004c 0100)
...

start ppc64le guest again. check the cpu info:
[root@dhcp112-244 ~]# cat /proc/cpuinfo 
processor	: 0
cpu		: POWER8 (architected), altivec supported
clock		: 3259.000000MHz
revision	: 1.0 (pvr 004c 0100)

processor	: 1
cpu		: POWER8 (architected), altivec supported
clock		: 3259.000000MHz
revision	: 1.0 (pvr 004c 0100)
...

It is POWER8 related cpu as expected.

So this bug is verified.

Comment 6 errata-xmlrpc 2016-11-07 21:13:15 UTC
Since the problem described in this bug report should be
resolved in a recent advisory, it has been closed with a
resolution of ERRATA.

For information on the advisory, and where to find the updated
files, follow the link below.

If the solution does not work for you, open a new bug report.

https://rhn.redhat.com/errata/RHBA-2016-2673.html