[libvirt-users] Broken OS when booting rootfs from 9p share

[Laine Stump]

On 02/24/2015 03:37 PM, Olivier Mauras wrote:
>> Hello,
>>
>> I've been trying to boot a VM with the rootfs being a 9P share from
>> the host. The VM OS is centos 7.
>> The OS boots but no services can work and it appears that the
>> authentication system is broken.
>>
>> Now the funny thing is that booting the same OS on the same 9P share
>> manually with Qemu works as expected with a fully functionnal OS... So
>> I'm wondering what could libvirt do that render the OS on the share
>> broken - Something with rights ?
>> Selinux is disabled on the host, and accessmode to the share is set to
>> passthrough in both cases.
>>
>> Here's my working Qemu line:
>> qemu
>> -kernel /srv/overlay/kernels/grsec-3.14.33-101/vmlinuz-3.14.33-101.el6.x86_64 \
>>
>> -initrd /srv/overlay/kernels/grsec-3.14.33-101/initramfs-3.14.33-101.el6.x86_64.img \
>>   -fsdev
>> local,id=r,path=/srv/overlay/run/irc,security_model=passthrough \
>>   -device virtio-9p-pci,fsdev=r,mount_tag=root \
>>   -nographic \
>>   -m 256M \
>>   -machine pc-i440fx-2.1,accel=kvm \
>>   -netdev tap,id=net0 -device
>> virtio-net,netdev=net0,mac=52:54:00:12:36:34 \
>>   -smp 1,sockets=1,cores=1 \
>>   -append 'root=virtfs:root rootflags=trans=virtio,version=9p2000.u ro
>> rootfstype=9p console=ttyS0'
>>
>> And here my libvirt VM config:
>> <domain type='kvm'>
>>   <name>irc</name>
>>   <uuid>ffbd32eb-a693-eadd-8923-18de80137472</uuid>
>>   <memory unit='KiB'>262144</memory>
>>   <currentMemory unit='KiB'>262144</currentMemory>
>>   <vcpu placement='static'>1</vcpu>
>>   <os>
>>     <type arch='x86_64' machine='pc-i440fx-2.1'>hvm</type>
>>
>> <kernel>/srv/overlay/kernels/grsec-3.14.33-101/vmlinuz-3.14.33-101.el6.x86_64</kernel>
>>
>> <initrd>/srv/overlay/kernels/grsec-3.14.33-101/initramfs-3.14.33-101.el6.x86_64.img</initrd>
>>     <cmdline>root=virtfs:root rootflags=trans=virtio,version=9p2000.u
>> ro rootfstype=9p</cmdline>
>>     <boot dev='hd'/>
>>   </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/qemu-system-x86_64</emulator>
>>     <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'/>
>>     <filesystem type='mount' accessmode='passthrough'>
>>       <source dir='/srv/overlay/run/irc'/>
>>       <target dir='root'/>
>>       <address type='pci' domain='0x0000' bus='0x00' slot='0x05'
>> function='0x0'/>
>>     </filesystem>
>>     <interface type='bridge'>
>>       <mac address='52:54:00:00:36:34'/>
>>       <source bridge='br0'/>
>>       <model type='virtio'/>
>>       <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>
>>     <input type='mouse' bus='ps2'/>
>>     <input type='keyboard' bus='ps2'/>
>>     <graphics type='vnc' port='-1' autoport='yes'/>
>>     <video>
>>       <model type='cirrus' vram='9216' 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='0x04'
>> function='0x0'/>
>>     </memballoon>
>>   </devices>
>> </domain>
>>
>>
>> My libvirt version is 1.2.9, and qemu is 2.1.2.
>>
>> Thanks for your help,
>>
>> Olivier
>>
>>  
>> _______________________________________________
>> libvirt-users mailing list
>> libvirt-users at redhat.com
>> https://www.redhat.com/mailman/listinfo/libvirt-users
> So I updated libvirt to 1.2.12 and qemu to 2.1.3 and it still gives me
> the exact same behaviour ... 
> Could it be that the share was created with an old version of
> virt-manager redenring in old/broken XML?  From Qemu config example i
> don't see how my XML could be incorrect.
>
> Any idea ?

I know nothing about the 9p filesystem, but since you have a qemu
commandline that works and a libvirt config that doesn't, the next
logical step would be to provide the non-working qemu commandline
generated by libvirt. You can find this at the end of the log file
/var/log/libvirt/qemu/irc.log.