[Bug 1473282] [NEW] Redhat guest hang when iotest on qemu 1:2.2+dfsg-5expubuntu9.2

[changlimin]

Public bug reported:

0. lsb_release -rd
  Description:    Ubuntu 15.04
  Release:        15.04

1. kvm --version , upgraded from ubuntu vivid-updates
  QEMU emulator version 2.2.0 (Debian 1:2.2+dfsg-5expubuntu9.2)

2. I create a Redhat 6.6 x64 virtual machine, then do iotest by using
tiotest tool provided by phoronix. The command is 3 instances of
"tiotest -b 512k -S".

3. After about 10-20 minutes, the guest io hang with the stack:
  [<ffffffff81041e98>] ? pvclock_clocksource_read+0x50/0xd0
  [<ffffffff811242d0>] ? sync_page+0x0/0x50
  [<ffffffff8152a1b3>] io_schedule+0x73/0xc0
  [<ffffffff8112430d>] sync_page+0x3d/0x50
  ......
  [<ffffffff811c07ce>] vfs_fsync_rage+0x7e/0x100
  ......
  [<ffffffff8118ea21>] sys_write+0x51/0x90

4. I check the code pvclock_clocksource_read, maybe the src->version is miswriten to an odd number.
  	do {
		version = __pvclock_read_cycles(src, &ret, &flags);
	} while ((src->version & 1) || version != src->version);

5. The vm xml:
<domain type='kvm'>
  <name>r0606-65b</name>
  <uuid>282b7680-09ea-4d12-b026-047800ea4629</uuid>
  <memory unit='KiB'>2097152</memory>
  <currentMemory unit='KiB'>2097152</currentMemory>
  <vcpu placement='static'>2</vcpu>
  <os>
    <type arch='x86_64' machine='pc-i440fx-2.2'>hvm</type>
    <boot dev='hd'/>
    <boot dev='cdrom'/>
  </os>
  <features>
    <acpi/>
    <apic/>
    <pae/>
  </features>
  <cpu>
    <topology sockets='2' cores='1' threads='1'/>
  </cpu>
  <clock offset='utc'/>
  <on_poweroff>destroy</on_poweroff>
  <on_reboot>restart</on_reboot>
  <on_crash>restart</on_crash>
  <devices>
    <emulator>/usr/bin/kvm</emulator>
    <disk type='file' device='disk'>
      <driver name='qemu' type='qcow2' cache='directsync'/>
      <source file='/vms/images/r0606-65b.img'/>
      <target dev='vda' bus='virtio'/>
      <address type='pci' domain='0x0000' bus='0x00' slot='0x08' function='0x0'/>
    </disk>
    <disk type='file' device='cdrom'>
      <driver name='qemu' type='raw'/>
      <target dev='hdd' bus='ide'/>
      <readonly/>
      <address type='drive' controller='0' bus='1' target='0' unit='1'/>
    </disk>
    <controller type='usb' index='0'>
      <address type='pci' domain='0x0000' bus='0x00' slot='0x01' function='0x2'/>
    </controller>
    <controller type='pci' index='0' model='pci-root'/>
    <controller type='ide' index='0'>
      <address type='pci' domain='0x0000' bus='0x00' slot='0x01' function='0x1'/>
    </controller>
    <controller type='virtio-serial' index='0'>
      <address type='pci' domain='0x0000' bus='0x00' slot='0x07' function='0x0'/>
    </controller>
    <interface type='bridge'>
      <mac address='0c:da:41:06:06:65'/>
      <source bridge='vswitch0'/>
      <model type='virtio'/>
      <driver name='qemu'/>
      <address type='pci' domain='0x0000' bus='0x00' slot='0x03' function='0x0'/>
    </interface>
    <serial type='pty'>
      <target port='0'/>
    </serial>
    <console type='pty'>
      <target type='serial' port='0'/>
    </console>
    <channel type='unix'>
      <source mode='bind' path='/var/lib/libvirt/qemu/r0606-65b.agent'/>
      <target type='virtio' name='org.qemu.guest_agent.0'/>
      <address type='virtio-serial' controller='0' bus='0' port='1'/>
    </channel>
    <input type='tablet' bus='usb'/>
    <input type='mouse' bus='ps2'/>
    <input type='keyboard' bus='ps2'/>
    <graphics type='vnc' port='-1' autoport='yes' listen='0.0.0.0'>
      <listen type='address' address='0.0.0.0'/>
    </graphics>
    <video>
      <model type='cirrus' vram='16384' heads='1'/>
      <address type='pci' domain='0x0000' bus='0x00' slot='0x02' function='0x0'/>
    </video>
    <memballoon model='virtio'>
      <address type='pci' domain='0x0000' bus='0x00' slot='0x09' function='0x0'/>
    </memballoon>
  </devices>
</domain>

** Affects: qemu (Ubuntu)
     Importance: Undecided
         Status: New

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Title:
  Redhat guest hang when iotest on qemu 1:2.2+dfsg-5expubuntu9.2

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