OK, that makes sense.  I was thinking that the MMIO transport would/could
support multiple register blocks and thus multiple devices.

On 5 July 2016 at 13:26, Laszlo Ersek (Red Hat) <email address hidden> wrote:

> A virtio-mmio "bus" is a single-device transport. It has a fixed base
> address that is set at board creation time. The MMIO area is 0x200 bytes
> in size, and hosts the virtio registers for one device that can sit on
> this transport. Transports can be unused.
>
> The "virt" machtype creates 32 transports (= 32 virtio-mmio "buses"
> suitable for one virtio device each). This allows for 32 virtio devices
> exposed via virtio-mmio. The placement of the different virtio-mmio
> "buses" at specific addresses in MMIO space is board specific.
>
> So yes, it definitely makes sense to create several of these "buses".
> It's better to think of a single virtio-mmio "bus" as a virtio-mmio
> "transport" or "register block". The "bus" terminology is just an
> internal QEMU detail. (It is not enumerable in hardware, for example.)
>
> --
> You received this bug notification because you are subscribed to the bug
> report.
> https://bugs.launchpad.net/bugs/1594239
>
> Title:
>   After adding more scsi disks for Aarch64 virtual machine, start the VM
>   and got Qemu Error
>
> Status in QEMU:
>   Confirmed
>
> Bug description:
>   Description
>   ===========
>   Using virt-manager to create a VM in Aarch64, Ubuntu 16.04.
>   Add scsi disk to the VM. After add four or more scsi disks, start the VM
> and will got Qemu error.
>
>   Steps to reproduce
>   ==================
>   1.Use virt-manager to create a VM.
>   2.After the VM is started, add scsi disk to the VM. They will be
> allocated to "sdb,sdc,sdd....." .
>   3.If we got a disk name > sdg, virt-manager will also assign a
> virtio-scsi controller for this disk.And the VM will be shutdown.
>   4.Start the VM, will see the error log.
>
>
>   Expected result
>   ===============
>   Start the vm smoothly.The added disks can work.
>
>   Actual result
>   =============
>   Got the error:
>   starting domain: internal error: process exited while connecting to
> monitor: qemu-system-aarch64:
> /build/qemu-zxCwKP/qemu-2.5+dfsg/migration/savevm.c:620:
> vmstate_register_with_alias_id: Assertion `!se->compat || se->instance_id
> == 0' failed.
>   details=Traceback (most recent call last):
>     File "/usr/share/virt-manager/virtManager/asyncjob.py", line 90, in
> cb_wrapper
>       callback(asyncjob, *args, **kwargs)
>     File "/usr/share/virt-manager/virtManager/asyncjob.py", line 126, in
> tmpcb
>       callback(*args, **kwargs)
>     File "/usr/share/virt-manager/virtManager/libvirtobject.py", line 83,
> in newfn
>       ret = fn(self, *args, **kwargs)
>     File "/usr/share/virt-manager/virtManager/domain.py", line 1402, in
> startup
>       self._backend.create()
>     File "/usr/local/lib/python2.7/dist-packages/libvirt.py", line 1035,
> in create
>       if ret == -1: raise libvirtError ('virDomainCreate() failed',
> dom=self)
>   libvirtError: internal error: process exited while connecting to
> monitor: qemu-system-aarch64:
> /build/qemu-zxCwKP/qemu-2.5+dfsg/migration/savevm.c:620:
> vmstate_register_with_alias_id: Assertion `!se->compat || se->instance_id
> == 0' failed.
>
>
>   Environment
>   ===========
>   1. virt-manager version is 1.3.2
>
>   2. Which hypervisor did you use?
>       Libvirt+KVM
>       $ kvm --version
>       QEMU emulator version 2.5.0 (Debian 1:2.5+dfsg-5ubuntu10.1),
> Copyright (c) 2003-2008 Fabrice Bellard
>       $ libvirtd --version
>       libvirtd (libvirt) 1.3.1
>
>   3. Which storage type did you use?
>      In the host file system,all in one physics machine.
>   stack@u202154:/opt/stack/nova$ df -hl
>   Filesystem Size Used Avail Use% Mounted on
>   udev 7.8G 0 7.8G 0% /dev
>   tmpfs 1.6G 61M 1.6G 4% /run
>   /dev/sda2 917G 41G 830G 5% /
>   tmpfs 7.9G 0 7.9G 0% /dev/shm
>   tmpfs 5.0M 0 5.0M 0% /run/lock
>   tmpfs 7.9G 0 7.9G 0% /sys/fs/cgroup
>   /dev/sda1 511M 888K 511M 1% /boot/efi
>   cgmfs 100K 0 100K 0% /run/cgmanager/fs
>   tmpfs 1.6G 0 1.6G 0% /run/user/1002
>   tmpfs 1.6G 0 1.6G 0% /run/user/1000
>   tmpfs 1.6G 0 1.6G 0% /run/user/0
>
>   4. Environment information:
>      Architecture : AARCH64
>      OS: Ubuntu 16.04
>
>   The Qemu commmand of libvirt is :
>   2016-06-20 02:39:46.561+0000: starting up libvirt version: 1.3.1,
> package: 1ubuntu10 (William Grant <email address hidden> Fri, 15 Apr 2016
> 12:08:21 +1000), qemu version: 2.5.0 (Debian 1:2.5+dfsg-5ubuntu10.1),
> hostname: u202154
>   LC_ALL=C
> PATH=/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin
> QEMU_AUDIO_DRV=none /usr/bin/kvm -name cent7 -S -machine
> virt,accel=kvm,usb=off -cpu host -drive
> file=/usr/share/edk2.git/aarch64/QEMU_EFI-pflash.raw,if=pflash,format=raw,unit=0,readonly=on
> -drive
> file=/var/lib/libvirt/qemu/nvram/cent7_VARS.fd,if=pflash,format=raw,unit=1
> -m 2048 -realtime mlock=off -smp 2,sockets=2,cores=1,threads=1 -uuid
> d5462bb6-159e-4dbd-9266-bf8c07fa1695 -nographic -no-user-config -nodefaults
> -chardev
> socket,id=charmonitor,path=/var/lib/libvirt/qemu/domain-cent7/monitor.sock,server,nowait
> -mon chardev=charmonitor,id=monitor,mode=control -rtc base=utc -no-shutdown
> -boot strict=on -device i82801b11-bridge,id=pci.1,bus=pcie.0,addr=0x1
> -device pci-bridge,chassis_nr=2,id=pci.2,bus=pci.1,addr=0x1 -device
> virtio-scsi-device,id=scsi0 -device lsi,id=scsi1 -device lsi,id=scsi2
> -device virtio-scsi-device,id=scsi3 -usb -drive
> file=/var/lib/libvirt/images/cent7-2.img,format=qcow2,if=none,id=drive-scsi0-0-0-0
> -device
> scsi-hd,bus=scsi0.0,channel=0,scsi-id=0,lun=0,drive=drive-scsi0-0-0-0,id=scsi0-0-0-0,bootindex=1
> -drive if=none,id=drive-scsi0-0-0-1,readonly=on -device
> scsi-cd,bus=scsi0.0,channel=0,scsi-id=0,lun=1,drive=drive-scsi0-0-0-1,id=scsi0-0-0-1
> -drive
> file=/var/lib/libvirt/images/cent7-10.img,format=qcow2,if=none,id=drive-scsi0-0-0-2
> -device
> scsi-hd,bus=scsi0.0,channel=0,scsi-id=0,lun=2,drive=drive-scsi0-0-0-2,id=scsi0-0-0-2
> -drive
> file=/var/lib/libvirt/images/cent7-11.img,format=qcow2,if=none,id=drive-scsi0-0-0-3
> -device
> scsi-hd,bus=scsi0.0,channel=0,scsi-id=0,lun=3,drive=drive-scsi0-0-0-3,id=scsi0-0-0-3
> -drive
> file=/var/lib/libvirt/images/cent7-13.img,format=qcow2,if=none,id=drive-scsi3-0-0-0
> -device
> scsi-hd,bus=scsi3.0,channel=0,scsi-id=0,lun=0,drive=drive-scsi3-0-0-0,id=scsi3-0-0-0
> -netdev tap,fd=33,id=hostnet0,vhost=on,vhostfd=35 -device
> virtio-net-device,netdev=hostnet0,id=net0,mac=52:54:00:a1:6e:75 -serial pty
> -msg timestamp=on
>   Domain id=11 is tainted: host-cpu
>
>   The libvirt xml is:
>   <domain type='kvm'>
>     <name>cent7</name>
>     <uuid>d5462bb6-159e-4dbd-9266-bf8c07fa1695</uuid>
>     <memory unit='KiB'>2097152</memory>
>     <currentMemory unit='KiB'>2097152</currentMemory>
>     <vcpu placement='static'>2</vcpu>
>     <os>
>       <type arch='aarch64' machine='virt'>hvm</type>
>       <loader readonly='yes'
> type='pflash'>/usr/share/edk2.git/aarch64/QEMU_EFI-pflash.raw</loader>
>       <nvram>/var/lib/libvirt/qemu/nvram/cent7_VARS.fd</nvram>
>       <boot dev='hd'/>
>     </os>
>     <cpu mode='host-passthrough'/>
>     <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'/>
>         <source file='/var/lib/libvirt/images/cent7-2.img'/>
>         <target dev='sda' bus='scsi'/>
>         <address type='drive' controller='0' bus='0' target='0' unit='0'/>
>       </disk>
>       <disk type='file' device='cdrom'>
>         <driver name='qemu' type='raw'/>
>         <target dev='sdb' bus='scsi'/>
>         <readonly/>
>         <address type='drive' controller='0' bus='0' target='0' unit='1'/>
>       </disk>
>       <disk type='file' device='disk'>
>         <driver name='qemu' type='qcow2'/>
>         <source file='/var/lib/libvirt/images/cent7-10.img'/>
>         <target dev='sdc' bus='scsi'/>
>         <address type='drive' controller='0' bus='0' target='0' unit='2'/>
>       </disk>
>       <disk type='file' device='disk'>
>         <driver name='qemu' type='qcow2'/>
>         <source file='/var/lib/libvirt/images/cent7-11.img'/>
>         <target dev='sdd' bus='scsi'/>
>         <address type='drive' controller='0' bus='0' target='0' unit='3'/>
>       </disk>
>       <disk type='file' device='disk'>
>         <driver name='qemu' type='qcow2'/>
>         <source file='/var/lib/libvirt/images/cent7-13.img'/>
>         <target dev='sdv' bus='scsi'/>
>         <address type='drive' controller='3' bus='0' target='0' unit='0'/>
>       </disk>
>       <controller type='scsi' index='0' model='virtio-scsi'>
>         <address type='virtio-mmio'/>
>       </controller>
>       <controller type='scsi' index='1'>
>         <address type='virtio-mmio'/>
>       </controller>
>       <controller type='scsi' index='2'>
>         <address type='virtio-mmio'/>
>       </controller>
>       <controller type='scsi' index='3' model='virtio-scsi'>
>         <address type='virtio-mmio'/>
>       </controller>
>       <controller type='pci' index='0' model='pcie-root'/>
>       <controller type='pci' index='1' model='dmi-to-pci-bridge'>
>         <model name='i82801b11-bridge'/>
>         <address type='pci' domain='0x0000' bus='0x00' slot='0x01'
> function='0x0'/>
>       </controller>
>       <controller type='pci' index='2' model='pci-bridge'>
>         <model name='pci-bridge'/>
>         <target chassisNr='2'/>
>         <address type='pci' domain='0x0000' bus='0x01' slot='0x01'
> function='0x0'/>
>       </controller>
>       <interface type='bridge'>
>         <mac address='52:54:00:a1:6e:75'/>
>         <source bridge='br0'/>
>         <model type='virtio'/>
>         <address type='virtio-mmio'/>
>       </interface>
>       <serial type='pty'>
>         <target port='0'/>
>       </serial>
>       <console type='pty'>
>         <target type='serial' port='0'/>
>       </console>
>     </devices>
>   </domain>
>
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