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Bug 1406749

Summary: Starting a VM that has memory equal to the max memory raising QEMU error
Product: [oVirt] ovirt-engine Reporter: Artyom <alukiano>
Component: BLL.VirtAssignee: jniederm
Status: CLOSED CURRENTRELEASE QA Contact: Artyom <alukiano>
Severity: medium Docs Contact:
Priority: high    
Version: 4.1.0CC: bugs, michal.skrivanek, tjelinek
Target Milestone: ovirt-4.1.0-betaKeywords: Triaged
Target Release: 4.1.0.2Flags: rule-engine: ovirt-4.1+
rule-engine: planning_ack+
tjelinek: devel_ack+
mavital: testing_ack+
Hardware: x86_64   
OS: Linux   
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Last Closed: 2017-02-01 14:38:26 UTC Type: Bug
Regression: --- Mount Type: ---
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oVirt Team: Virt RHEL 7.3 requirements from Atomic Host:
Cloudforms Team: --- Target Upstream Version:
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Description Artyom 2016-12-21 11:46:03 UTC 
Description of problem:
Starting a VM that has memory equal to the max memory raising QEMU error
2016-12-21 11:26:28.804+0000: 17651: info : virObjectUnref:259 : OBJECT_UNREF: obj=0x7fcd141c13e0
2016-12-21T11:26:28.884494Z qemu-kvm: -m size=21911552k,slots=16,maxmem=21911552k: invalid value of -m option maxmem: memory slots were specified but maximum memory size (0x539600000) is equal to the initial memory size (0x539600000)
2016-12-21 11:26:28.949+0000: shutting down

Version-Release number of selected component (if applicable):
# rpm -qa | grep qemu
qemu-kvm-common-rhev-2.6.0-28.el7_3.2.x86_64
ipxe-roms-qemu-20160127-5.git6366fa7a.el7.noarch
libvirt-daemon-driver-qemu-2.0.0-10.el7.x86_64
qemu-img-rhev-2.6.0-28.el7_3.2.x86_64
qemu-kvm-rhev-2.6.0-28.el7_3.2.x86_64
qemu-kvm-tools-rhev-2.6.0-28.el7_3.2.x86_64

ovirt-engine-4.1.0-0.2.master.20161218144454.gitbaa2853.el7.centos.noarch

How reproducible:
Always

Steps to Reproduce:
1. Update VM max memory parameter to be equal to memory parameter
2. Start the VM
3.

Actual results:
VM failed to start with the QEMU error

Expected results:
I believe we must add validation on the updateVm action to prevent updating a VM with the max memory equal to the memory

Additional info:
Comment 1 Michal Skrivanek 2016-12-22 07:43:25 UTC 
the easiest fix might be to set the max size +4K when equal. Difference in reporting should be negligent and it seems to be enough to fool qemu. Better than trying to introduce a hotpluggable and non-hotpluggable VMs differentiation right now
Comment 2 Michal Skrivanek 2016-12-22 07:52:30 UTC 
(In reply to Michal Skrivanek from comment #1)
> the easiest fix might be to set the max size +4K when equal.
I mean to send it like that, not persist. Perhaps do that even only in vdsm
Comment 3 Artyom 2017-01-11 09:38:18 UTC 
Verified on ovirt-engine-4.1.0-0.4.master.20170110134514.git1586fd4.el7.centos.noarch

Run the VM with the maxMemory = memory:
# virsh -r dumpxml 47 | grep -i memory
  <memory unit='KiB'>1048576</memory>
  <currentMemory unit='KiB'>1048576</currentMemory>
      <cell id='0' cpus='0' memory='1048576' unit='KiB'/>

Run the VM with the maxMemory != memory:
# virsh -r dumpxml 46 | grep -i memory
  <maxMemory slots='16' unit='KiB'>2097152</maxMemory>
  <memory unit='KiB'>1048576</memory>
  <currentMemory unit='KiB'>1048576</currentMemory>
      <cell id='0' cpus='0' memory='1048576' unit='KiB'/>