[Qemu-devel] VMState assertion for USB devices on multiple buses

[Daniel P. Berrange]

I've been experimenting with multiple USB2 buses, and device physical port
addressing. It seems if you have 2 devices of the same type on the same
port, but in different buses, you get a bogus VMState assertion failure

    # qemu-system-x86_64 \
       -nodefconfig -nodefaults \
       -vnc 127.0.0.1:0 -vga cirrus -monitor stdio \
       -device ich9-usb-ehci1,addr=1d.7,multifunction=on,id=ehci0 \
       -device 
ich9-usb-uhci1,addr=1d.0,multifunction=on,id=uhci0-1,masterbus=ehci0.0,firstport=0
 \
       -device 
ich9-usb-uhci2,addr=1d.1,multifunction=on,id=uhci0-2,masterbus=ehci0.0,firstport=2
 \
       -device 
ich9-usb-uhci3,addr=1d.2,multifunction=on,id=uhci0-3,masterbus=ehci0.0,firstport=4
 \
       -device usb-tablet,bus=ehci0.0,port=1,id=t1  \
       -device ich9-usb-ehci1,addr=1c.7,multifunction=on,id=ehci1 \
       -device 
ich9-usb-uhci1,addr=1c.0,multifunction=on,id=uhci1-1,masterbus=ehci1.0,firstport=0
 \
       -device 
ich9-usb-uhci2,addr=1c.1,multifunction=on,id=uhci1-2,masterbus=ehci1.0,firstport=2
 \
       -device 
ich9-usb-uhci3,addr=1c.2,multifunction=on,id=uhci1-3,masterbus=ehci1.0,firstport=4
 \
       -device usb-tablet,bus=ehci1.0,port=1,id=t2
    *** EHCI support is under development ***
    *** EHCI support is under development ***
    qemu-system-x86_64: savevm.c:1260: vmstate_register_with_alias_id: 
Assertion `!se->compat || se->instance_id == 0' failed.
    Aborted

If I have a CCID on one bus, and tablet on the other it works

    # qemu-system-x86_64 \
       -nodefconfig -nodefaults \
       -vnc 127.0.0.1:0 -vga cirrus -monitor stdio \
       -device ich9-usb-ehci1,addr=1d.7,multifunction=on,id=ehci0 \
       -device 
ich9-usb-uhci1,addr=1d.0,multifunction=on,id=uhci0-1,masterbus=ehci0.0,firstport=0
 \
       -device 
ich9-usb-uhci2,addr=1d.1,multifunction=on,id=uhci0-2,masterbus=ehci0.0,firstport=2
 \
       -device 
ich9-usb-uhci3,addr=1d.2,multifunction=on,id=uhci0-3,masterbus=ehci0.0,firstport=4
 \
       -device usb-tablet,bus=ehci0.0,port=1,id=t1  \
       -device ich9-usb-ehci1,addr=1c.7,multifunction=on,id=ehci1 \
       -device 
ich9-usb-uhci1,addr=1c.0,multifunction=on,id=uhci1-1,masterbus=ehci1.0,firstport=0
 \
       -device 
ich9-usb-uhci2,addr=1c.1,multifunction=on,id=uhci1-2,masterbus=ehci1.0,firstport=2
 \
       -device 
ich9-usb-uhci3,addr=1c.2,multifunction=on,id=uhci1-3,masterbus=ehci1.0,firstport=4
 \
       -device usb-ccid,bus=ehci1.0,port=1,id=t2

But if I have 2 CCID devices, then I see failure again

    # qemu-system-x86_64 \
       -nodefconfig -nodefaults \
       -vnc 127.0.0.1:0 -vga cirrus -monitor stdio \
       -device ich9-usb-ehci1,addr=1d.7,multifunction=on,id=ehci0 \
       -device 
ich9-usb-uhci1,addr=1d.0,multifunction=on,id=uhci0-1,masterbus=ehci0.0,firstport=0
 \
       -device 
ich9-usb-uhci2,addr=1d.1,multifunction=on,id=uhci0-2,masterbus=ehci0.0,firstport=2
 \
       -device 
ich9-usb-uhci3,addr=1d.2,multifunction=on,id=uhci0-3,masterbus=ehci0.0,firstport=4
 \
       -device usb-ccid,bus=ehci0.0,port=1,id=t1  \
       -device ich9-usb-ehci1,addr=1c.7,multifunction=on,id=ehci1 \
       -device 
ich9-usb-uhci1,addr=1c.0,multifunction=on,id=uhci1-1,masterbus=ehci1.0,firstport=0
 \
       -device 
ich9-usb-uhci2,addr=1c.1,multifunction=on,id=uhci1-2,masterbus=ehci1.0,firstport=2
 \
       -device 
ich9-usb-uhci3,addr=1c.2,multifunction=on,id=uhci1-3,masterbus=ehci1.0,firstport=4
 \
       -device usb-ccid,bus=ehci1.0,port=1,id=t2
    *** EHCI support is under development ***
    *** EHCI support is under development ***
    qemu-system-x86_64: savevm.c:1260: vmstate_register_with_alias_id: 
Assertion `!se->compat || se->instance_id == 0' failed.
    Aborted


AFAICT, the problem is that the 'se->idstr' field in the SaveStateEntry
struct is not getting a unique enough value.

Both the USB devices get idstr named   "1/usb-ccid", which IIUC is a
combination of the device type and the port number.

IMHO, it needs to have the USB bus name in there too eg. in this
example it should have been

    ehci0.0/1/usb-ccid
    ehci1.0/1/usb-ccid

Regrads,
Daniel
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