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Bug 1094285

Summary: Hot plug CPU not working with RHEL6 machine types running on RHEL7 host.
Product: Red Hat Enterprise Linux 7 Reporter: Karen Noel <knoel>
Component: qemu-kvmAssignee: Paolo Bonzini <pbonzini>
Status: CLOSED ERRATA QA Contact: Virtualization Bugs <virt-bugs>
Severity: high Docs Contact:
Priority: unspecified    
Version: 7.0CC: areis, flang, gklein, hhuang, iheim, imammedo, jherrman, juzhang, knoel, lersek, lpeer, michal.skrivanek, michen, mkalinin, mrezanin, nsednev, pbonzini, qzhang, rbalakri, Rhev-m-bugs, virt-maint, xfu, yeylon
Target Milestone: rcKeywords: ZStream
Target Release: ---   
Hardware: x86_64   
OS: Linux   
Whiteboard: virt
Fixed In Version: qemu-kvm-1.5.3-62.el7 Doc Type: Bug Fix
Doc Text:
Previously, an internal error prevented KVM from executing a CPU hot plug on a Red Hat Enterprise Linux 7 guest running on a Red Hat Enterprise Linux 7 host. This update addresses the internal error and CPU hot plugging in the described scenario now functions correctly.
 Story Points: ---
Clone Of: 1093411 Environment:
Last Closed: 2015-03-05 08:06:47 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:    
Bug Blocks: 1076184, 1093411, 1094820    
Attachments:
Description Flags
[RHEL-7.0 qemu-kvm PATCH] pc: enable CPU hotplug for RHEL6.{45}u PIIX machines and disable it for Q35 none

Comment 1 Paolo Bonzini 2014-05-05 13:48:34 UTC 
I can take care of this, the fix is trivial.
Comment 3 FuXiangChun 2014-05-06 02:07:01 UTC 
Reproduced this issue with qemu-kvm-rhev-1.5.3-60.el7ev.x86_64.

steps:
1.Boot qemu-kvm process as following command line
/usr/libexec/qemu-kvm -M rhel6.x.x -m 8G -smp 4,sockets=2,cores=2,thread=1,maxcpus=160 .......

2. check vcpu number 
(qemu) info cpus
* CPU #0: pc=0x00000000000fe7e0 thread_id=32603
  CPU #1: pc=0x00000000000f6277 (halted) thread_id=32604
  CPU #2: pc=0x00000000000f6277 (halted) thread_id=32605
  CPU #3: pc=0x00000000000f6277 (halted) thread_id=32606

3. hotplug vcpu via qmp command
{ "execute": "cpu-add", "arguments": { "id": 4 }}

result:
{"error": {"class": "GenericError", "desc": "Not supported"}}

4. re-check vcpu number
(qemu) info cpus
* CPU #0: pc=0x00000000000fe7e0 thread_id=32603
  CPU #1: pc=0x00000000000f6277 (halted) thread_id=32604
  CPU #2: pc=0x00000000000f6277 (halted) thread_id=32605
  CPU #3: pc=0x00000000000f6277 (halted) thread_id=32606

Notes:
QE tested -M rhel6.0.0 ~ rhel6.5.0. All machine type rhel6.x.x don't work.
Comment 4 Igor Mammedov 2014-05-06 07:45:17 UTC 
Created attachment 892795 [details]
[RHEL-7.0 qemu-kvm PATCH] pc: enable CPU hotplug for RHEL6.{45}u PIIX machines and disable it for Q35
Comment 5 Igor Mammedov 2014-05-06 11:37:26 UTC 
Comment on attachment 892795 [details]
[RHEL-7.0 qemu-kvm PATCH] pc: enable CPU hotplug for RHEL6.{45}u PIIX machines and disable it for Q35

it was a wrong patch.
Comment 9 langfang 2014-11-28 03:11:40 UTC 
Reproduce this bug as follow version:
Host:
# uname -r
3.10.0-210.el7.x86_64
# rpm -q qemu-kvm-rhev
qemu-kvm-rhev-1.5.3-60.el7ev.x86_64


guest:
win2012r2

Steps:
1.Boot guest with "-M rhel6.5.0"
...-smp 2,maxcpus=8...

2.Hotadd vcpu
{ "execute": "cpu-add", "arguments": { "id":2 }}
{"error": {"class": "GenericError", "desc": "Not supported"}}

Results: Not support

Verify this bug as follow version:

Version:
# uname -r
3.10.0-210.el7.x86_64
# rpm -q qemu-kvm-rhev
qemu-kvm-rhev-1.5.3-82.el7ev.x86_64

Guest:wini2012r2

Steps 
1.Boot guest with "-M rhel6.5.0"
...-M rhel6.5.0...-smp 2,maxcpus=8...

2.Hotadd vcpu
{ "execute": "cpu-add", "arguments": { "id":2 }}
{ "execute": "cpu-add", "arguments": { "id":3 }}


3.Tried the same steps for "-M rhel6.4.0/rhel6.3.0/rhel6.2.0/rhel6.1.0/rhel6.0.0/pc-i440fx-rhel7.0.0

Results:
...
{ "execute": "cpu-add", "arguments": { "id":2 }}
{"return": {}}
{ "execute": "cpu-add", "arguments": { "id":3 }}
{"return": {}}


In guest: can be see the new add vcpu

Addtinonal info:
1.Also tried rhel6 guest,work well
2.Tried on AMD machine,work well


According to above test ,this bug has been fixed.
Comment 12 errata-xmlrpc 2015-03-05 08:06:47 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/RHSA-2015-0349.html