+++ This bug was initially created as a clone of Bug #1049844 +++

Description of problem:
Fail to do S4 after change running guest's memory from 4G to 2G

Version-Release number of selected component (if applicable):
kernel-3.10.0-65.el7.x86_64
libvirt-1.1.1-17.el7.x86_64
qemu-kvm-rhev-1.5.3-31.el7.x86_64
qemu-guest-agent-1.5.3-31.el7.x86_64

How reproducible:
100%

Steps to Reproduce:
1.Prepare a rhel7 guest with qemu-guest-agent service installing and with 4G memory
#virsh start qcow22 (with 4G mem)
# virsh list
 Id    Name                           State
----------------------------------------------------
 35    qcow22                         running
# virsh dominfo qcow22
 Id:             35
 Name:           qcow22
 UUID:           f0295000-dc19-481e-8379-8592c5e437f8
 OS Type:        hvm
 State:          running
 CPU(s):         1
 CPU time:       11.7s
 Max memory:     4194304 KiB
 Used memory:    4194304 KiB
 Persistent:     yes
 Autostart:      disable
 Managed save:   no
 Security model: selinux
 Security DOI:   0
 Security label: system_u:system_r:svirt_t:s0:c53,c111 (enforcing)
2.set the guest's memory to 2G
# virsh setmem qcow22 2G

# virsh dominfo qcow22
 Id:             35
 Name:           qcow22
 UUID:           f0295000-dc19-481e-8379-8592c5e437f8
 OS Type:        hvm
 State:          running
 CPU(s):         1
 CPU time:       12.5s
 Max memory:     4194304 KiB
 Used memory:    2097152 KiB
 Persistent:     yes
 Autostart:      disable
 Managed save:   no
 Security model: selinux
 Security DOI:   0
 Security label: system_u:system_r:svirt_t:s0:c53,c111 (enforcing)

3. DO S3/S4 on the host, the S3 can be excuted successfully, however will fail to do S4.
# virsh dompmsuspend qcow22 --target mem
Domain qcow22 successfully suspended
# virsh list
 Id    Name                           State
----------------------------------------------------
 2     qcow22                          pmsuspended

# virsh dompmwakeup qcow222
Domain qcow22 successfully woken up

# virsh dompmsuspend qcow22 --target disk
error: Domain qcow22 could not be suspended
error: internal error: unable to execute QEMU agent command 'guest-suspend-disk': child process has failed to suspend

4.I can also hit this issue on rhel6.5

Actual Results:
Failed to do S4 after change running guest's memory from 4G to 2G
Expected results:
Succeed in doing S4 after change running guest's memory from 4G to 2G

Additional info: