[Qemu-devel] [Bug 1562653] Re: Ubuntu 15.10: QEMU VM hang if memory >= 1T

["Christian Ehrhardt " <1562653@bugs.launchpad.net>]

I only saw this because it expired now :-/

Anyone affected by this might want to take a look at bug 1776189 where
Ubuntu added a special machine type to more easily set "host-phys-bits"
which is the qemu flag to have more (usually the host has more)
available (at the cost of migratability). That allows <1TB as the
default bits in qemu are chosen on the base of TCG (to be able to
emulate what is virtualized) and that is limited to 1TB.

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https://bugs.launchpad.net/bugs/1562653

Title:
  Ubuntu 15.10: QEMU VM hang if memory >= 1T

Status in QEMU:
  Expired
Status in qemu package in Ubuntu:
  Expired

Bug description:
  1. Ubuntu 15.10 x86_64 installed on HP SuperDome X with 8CPUs and 4T
  memory.

  2. Create a VM, install Ubuntu 15.10, if memory >= 1T , VM hang when start. If memory < 1T, it is good.
  <domain type='kvm'>
    <name>u1510-1</name>
    <uuid>39eefe1e-4829-4843-b892-026d143f3ec7</uuid>
    <memory unit='KiB'>1073741824</memory>
    <currentMemory unit='KiB'>1073741824</currentMemory>
    <vcpu placement='static'>16</vcpu>
    <os>
      <type arch='x86_64' machine='pc-i440fx-2.3'>hvm</type>
      <boot dev='hd'/>
      <boot dev='cdrom'/>
    </os>
    <features>
      <acpi/>
      <apic/>
      <pae/>
    </features>
    <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/u1510-1.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='hdc' bus='ide'/>
        <readonly/>
        <address type='drive' controller='0' bus='1' target='0' unit='0'/>
      </disk>
      <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='usb' index='0'>
        <address type='pci' domain='0x0000' bus='0x00' slot='0x01' function='0x2'/>
      </controller>
      <interface type='bridge'>
        <mac address='0c:da:41:1d:ae:f1'/>
        <source bridge='vswitch0'/>
        <model type='virtio'/>
        <driver name='vhost'/>
        <address type='pci' domain='0x0000' bus='0x00' slot='0x03' function='0x0'/>
      </interface>
      <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>

  3. The panic stack is
    ... cannot show
    async_page_fault+0x28
    ioread32_rep+0x38
    ata_sff_data_xfer32+0x8a
    ata_pio_sector+0x93
    ata_pio_sectors+0x34
    ata_sff_hsm_move+0x226
    RIP: kthread_data+0x10
    CR2: FFFFFFFF_FFFFFFD8

  4. Change the host os to Redhat 7.2 , the vm is good even memory
  >=3.8T.

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