[Bug 1612424] Comment bridged from LTC Bugzilla

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------- Comment From nasastry at in.ibm.com 2016-08-13 15:03 EDT-------
(In reply to comment #10)
> (In reply to comment #9)
> > You say that this is because of a ddw bugfix in the qemu in PowerKVM.  Which
> > version of qemu, or which version of PowerKVM, includes this change?

qemu-2.5-6.el7_1.pkvm3_1_1.2200.0 contains the fix for DDW issue of
QEMU.

> > is this reproducible with the qemu in some version of Ubuntu, and if
so, which version(s)?

I have tried Ubuntu14.04.5 as a guest, here I can see the problem with
the qemu mentioned above i.e. 2.5-6 of PowerKVM host.

> >
> > What are the steps to reproduce the failure?
1. Prepare the guest for memory hot plug, by adding the following tags to the guest's xml. Here I have a guest with NUMA support

<maxMemory slots='32' unit='KiB'>134217728</maxMemory>
<memory unit='KiB'>73400320</memory>
<currentMemory unit='KiB'>73400320</currentMemory>
<vcpu placement='static' current='24'>32</vcpu>
<cpu>
<topology sockets='32' cores='1' threads='1'/>
<numa>
<cell id='0' cpus='0,4,8,12,16,20,24,28' memory='2097152' unit='KiB'/>
<cell id='1' cpus='1,5,9,13,17,21,25,29' memory='2097152' unit='KiB'/>
<cell id='2' cpus='2,6,10,14,18,22,26,30' memory='2097152' unit='KiB'/>
<cell id='3' cpus='3,7,11,15,19,23,27,31' memory='2097152' unit='KiB'/>
</numa>
</cpu>

2. define the guest, start the guest, log in and check the current memory.
virsh define <filename.xml>
virsh start <domain name> --console
log in
cat /proc/meminfo | grep -i memtotal

3. From Host, hot plug the memory using the following command
virsh attach-device <domain name> men_hp.xml --live

mem_hp.xml  for hot plugging 8G is given below, change the value
according to your environment.

<memory model='dimm'>
<target>
<size unit='KiB'>8388608</size>
<node>0</node>
</target>
</memory>

4. In the guest Memory value should have increased by 8GB, but there
will be no change.

5. From Guest OS /var/log/drmgr
[root at localhost ~]# cat /var/log/drmgr
...
drmgr: -c mem -a -q 1
Validating Memory DLPAR capability...yes.
Maximum of 496 LMBs
Could not find LMB with drc-index of 0
Found 0 LMBs currently allocated
Could not gather LMB (logical memory block information.

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https://bugs.launchpad.net/bugs/1612424

Title:
  Ubuntu14.04.05 To get memory hotplug working in PowerKVM, powerpc-
  utils needs update to version 1.3.0

Status in powerpc-utils package in Ubuntu:
  New

Bug description:
  == Comment: #0 - NAGESWARA R. SASTRY - 2016-07-25 01:56:38 ==
  ---Problem Description---
  For memory hot plug to work properly, powerpc-utils needs to be updated to at least 1.3.0 version
   
  ---uname output---
  Linux ubuntu1404 4.4.0-28-generic #47~14.04.1-Ubuntu SMP Fri Jun 24 16:30:24 UTC 2016 ppc64le ppc64le ppc64le GNU/Linux

   
  ---Steps to Reproduce---
   Existing version of powerpc-utils is 1.2.18+r1.1.3-24ubuntu1              this has to be updated to at least 1.3.0 version.
   
  Userspace rpm: powerpc-utils                      1.2.18+r1.1.3-24ubuntu1              ppc64el  

  == Comment: #4 - NAGESWARA R. SASTRY - 2016-07-27 01:33:19 ==
  (In reply to comment #3)
  > 
  > Can you, or someone expand on the description of memory hotplug not working.
  > What exactly is not working?

  Because of the QEMU changes (ddw related bug fix), memory hot plug
  stopped working. 'Not working' in the sense when a user hot plug
  memory from Host->Guest with powerpc-utils less than 1.3.0 version,
  hot plug action will not full fill. 'drmgr' fails to identify free
  LMBs.

  To resolve the above issue, the following patches are required to be
  in powerpc-utils

  From https://bugzilla.linux.ibm.com/show_bug.cgi?id=143794#c4
  ...
  The following 2 commits of powerpc-utils are required for memory hotplug to work:

  f4006893d84: drmgr: Correct return code from set_mem_scn_state()
  4f515ea179c: drmgr: Correct LMB counting when discovering LMBs

  These are part of powerpc-utils-1.3.0 which is the next release after
  1.2.27.

  We should now get at least 1.3.0 version in all the supported distros.
  ...

  Hope the above information helps.
  Thanks!!

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