Paolo,
I bisected
commit a0710f7995f914e3044e5899bd8ff6c43c62f916
Author: Paolo Bonzini <pbonz...@redhat.com>
AuthorDate: Fri Feb 20 17:26:52 2015 +0100
Commit: Kevin Wolf <kw...@redhat.com>
CommitDate: Tue Apr 28 15:36:08 2015 +0200
iothread: release iothread around aio_poll
to cause a problem with hanging guests.
Having many guests all with a kernel/ramdisk (via -kernel) and
several null block devices will result in hangs. All hanging
guests are in partition detection code waiting for an I/O to return
so very early maybe even the first I/O.
Reverting that commit "fixes" the hangs.
Any ideas?
Christian
PS: A guest xml looks like
<domain type='kvm' xmlns:qemu='http://libvirt.org/schemas/domain/qemu/1.0'>
<name>test2</name>
<uuid>13bd8253-9abb-4be8-9399-73b899762aaa</uuid>
<memory unit='KiB'>286720</memory>
<currentMemory unit='KiB'>286720</currentMemory>
<vcpu placement='static'>10</vcpu>
<iothreads>8</iothreads>
<cputune>
<shares>12</shares>
</cputune>
<os>
<type arch='s390x' machine='s390-ccw-virtio'>hvm</type>
<kernel>/boot/vmlinux-4.0.0+</kernel>
<initrd>/boot/ramdisk.reboot</initrd>
<cmdline>root=/dev/ram0</cmdline>
<boot dev='hd'/>
</os>
<clock offset='utc'/>
<on_poweroff>destroy</on_poweroff>
<on_reboot>restart</on_reboot>
<on_crash>preserve</on_crash>
<devices>
<controller type='usb' index='0' model='none'/>
<console type='pty'>
<target type='sclp' port='0'/>
</console>
<memballoon model='none'/>
</devices>
<qemu:commandline>
<qemu:arg value='-drive'/>
<qemu:arg value='driver=null-aio,id=null1,if=none,size=100G'/>
<qemu:arg value='-device'/>
<qemu:arg
value='virtio-blk-ccw,drive=null1,serial=null1,iothread=iothread1'/>
<qemu:arg value='-drive'/>
<qemu:arg value='driver=null-aio,id=null2,if=none,size=100G'/>
<qemu:arg value='-device'/>
<qemu:arg
value='virtio-blk-ccw,drive=null2,serial=null2,iothread=iothread2'/>
<qemu:arg value='-drive'/>
<qemu:arg value='driver=null-aio,id=null3,if=none,size=100G'/>
<qemu:arg value='-device'/>
<qemu:arg
value='virtio-blk-ccw,drive=null3,serial=null3,iothread=iothread3'/>
<qemu:arg value='-drive'/>
<qemu:arg value='driver=null-aio,id=null4,if=none,size=100G'/>
<qemu:arg value='-device'/>
<qemu:arg
value='virtio-blk-ccw,drive=null4,serial=null4,iothread=iothread4'/>
<qemu:arg value='-drive'/>
<qemu:arg value='driver=null-aio,id=null5,if=none,size=100G'/>
<qemu:arg value='-device'/>
<qemu:arg
value='virtio-blk-ccw,drive=null5,serial=null5,iothread=iothread5'/>
<qemu:arg value='-drive'/>
<qemu:arg value='driver=null-aio,id=null6,if=none,size=100G'/>
<qemu:arg value='-device'/>
<qemu:arg
value='virtio-blk-ccw,drive=null6,serial=null6,iothread=iothread6'/>
<qemu:arg value='-drive'/>
<qemu:arg value='driver=null-aio,id=null7,if=none,size=100G'/>
<qemu:arg value='-device'/>
<qemu:arg
value='virtio-blk-ccw,drive=null7,serial=null7,iothread=iothread7'/>
<qemu:arg value='-drive'/>
<qemu:arg value='driver=null-aio,id=null8,if=none,size=100G'/>
<qemu:arg value='-device'/>
<qemu:arg
value='virtio-blk-ccw,drive=null8,serial=null8,iothread=iothread8'/>
</qemu:commandline>
</domain>
