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Bug 1361443

Summary: ppc64le: Introduce stable cpu_index for cpu hotplugging
Product: Red Hat Enterprise Linux 7 Reporter: David Gibson <dgibson>
Component: qemu-kvm-rhevAssignee: David Gibson <dgibson>
Status: CLOSED ERRATA QA Contact: Virtualization Bugs <virt-bugs>
Severity: urgent Docs Contact:
Priority: unspecified    
Version: 7.3CC: bugproxy, dyuan, dzheng, gsun, hannsj_uhl, knoel, qzhang, virt-maint, xuhan, xuma
Target Milestone: rc   
Target Release: 7.3   
Hardware: ppc64le   
OS: Linux   
Whiteboard:
Fixed In Version: qemu-kvm-rhev-2.6.0-19.el7 Doc Type: If docs needed, set a value
Doc Text:
Story Points: ---
Clone Of: Environment:
Last Closed: 2016-11-07 21:27:10 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: 1172917    
Bug Blocks: 1299677, 1359843    

Description David Gibson 2016-07-29 05:55:04 UTC 
Description of problem:

Although we've merged downstream the qemu patches to add support for vcpu hotplug on Power, we're missing the follow up patches which fix problems with cpu_index allocation.  Depending on exact version that either means it's not possible to plug cpu cores "out of order" or that if you do, migration will fail. 

Version-Release number of selected component (if applicable):

qemu-kvm-rhev-2.6.0-16.el7.ppc64le

How reproducible:

100%

Steps to Reproduce:
1. Start a VM with >2 possible cpu cores, but only 1 initial core
2. Attempt to hotplug the last core
3. Attempt to migrate the VM

Actual results:

Depending on exact version, either an error at step #2, or an error in step #3.

Expected results:

Hotplug succeeds and so does migration.

Additional info:
Comment 1 David Gibson 2016-07-29 05:56:33 UTC 
This bug depends on bug 1172917 in terms of application order, but in order to test bug 1172917 we'll need the fix to this bug.  Not sure which way around the depends should go here.
Comment 4 Miroslav Rezanina 2016-08-05 10:57:41 UTC 
Fix included in qemu-kvm-rhev-2.6.0-19.el7
Comment 6 Xujun Ma 2016-08-11 02:28:34 UTC 
Reproduced the issue on old version:

Version-Release number of selected component (if applicable):
kernel-3.10.0-481.el7.ppc64le
qemu-kvm-rhev-2.6.0-16.el7.ppc64le
SLOF-20160223-5.gitdbbfda4.el7.noarch


Steps to Reproduce:


1.Boot up a guest with with command:
/usr/libexec/qemu-kvm \
 -name xuma-test \
 -smp 1,maxcpus=3,sockets=1,cores=1,threads=1 \
 -m 1024 \
 -monitor stdio \
 -vnc :20 \
 -qmp tcp:0:4444,server,nowait \
 -device virtio-scsi-pci,bus=pci.0 \
 -device scsi-hd,id=scsi-hd0,drive=scsi-hd0-dr0,bootindex=0 \
 -drive file=/root/RHEL-7.2.qcow2,if=none,id=scsi-hd0-dr0,format=qcow2,cache=none \
 -device virtio-net-pci,netdev=net0,id=nic0,mac=52:54:00:c4:e7:84 \
 -netdev tap,id=net0,script=/etc/qemu-ifup,downscript=/etc/qemu-ifdown,vhost=on \
 

2.check cpus in hmp then hotplug last core:
(qemu) info hotpluggable-cpus 
Hotpluggable CPUs:
  type: "host-spapr-cpu-core"
  vcpus_count: "1"
  CPUInstance Properties:
    core-id: "16"
  type: "host-spapr-cpu-core"
  vcpus_count: "1"
  CPUInstance Properties:
    core-id: "8"
  type: "host-spapr-cpu-core"
  vcpus_count: "1"
  qom_path: "/machine/unattached/device[1]"
  CPUInstance Properties:
    core-id: "0"
(qemu) device_add host-spapr-cpu-core,core-id=16
(qemu) info hotpluggable-cpus 
Hotpluggable CPUs:
  type: "host-spapr-cpu-core"
  vcpus_count: "1"
  qom_path: "/machine/peripheral-anon/device[1]"
  CPUInstance Properties:
    core-id: "16"
  type: "host-spapr-cpu-core"
  vcpus_count: "1"
  CPUInstance Properties:
    core-id: "8"
  type: "host-spapr-cpu-core"
  vcpus_count: "1"
  qom_path: "/machine/unattached/device[1]"
  CPUInstance Properties:
    core-id: "0"

3.boot up destination vm and hotplug last core:
/usr/libexec/qemu-kvm \
 -name xuma-test \
 -smp 1,maxcpus=3,sockets=1,cores=1,threads=1 \
 -m 1024 \
 -monitor stdio \
 -vnc :20 \
 -qmp tcp:0:4444,server,nowait \
 -device virtio-scsi-pci,bus=pci.0 \
 -device scsi-hd,id=scsi-hd0,drive=scsi-hd0-dr0,bootindex=0 \
 -drive file=/root/RHEL-7.2.qcow2,if=none,id=scsi-hd0-dr0,format=qcow2,cache=none \
 -device virtio-net-pci,netdev=net0,id=nic0,mac=52:54:00:c4:e7:84 \
 -netdev tap,id=net0,script=/etc/qemu-ifup,downscript=/etc/qemu-ifdown,vhost=on \
 -incoming tcp:0:7777
(qemu) device_add host-spapr-cpu-core,core-id=16

4.migrate vm in source vm hmp
(qemu) migrate tcp:0:7777


Actual results:
hotplugging cpu succeeded ,and migration failed with error information:
qemu-kvm: socket_writev_buffer: Got err=104 for (131328/18446744073709551615)


Verified the issue on the latest build:
Version-Release number of selected component (if applicable):
kernel-3.10.0-481.el7.ppc64le
qemu-kvm-rhev-2.6.0-19.el7.ppc64le
SLOF-20160223-5.gitdbbfda4.el7.noarch

Steps to Reproduce:
The same steps as above


Actual results:
hotplugging cpu and migration succeeded

Base on the above results ，the bug has been fixed.
Comment 8 errata-xmlrpc 2016-11-07 21:27:10 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