Re: [Qemu-devel] [qom-next] Bisecting virtio-scsi issue

[Avi Kivity]

On 06/17/2012 05:08 PM, Andreas Färber wrote:
> Am 17.06.2012 10:37, schrieb Avi Kivity:
>> On 06/16/2012 03:41 AM, Andreas Färber wrote:
>>> Hi,
>>>
>>> After multiple runs of not-so-successful bisecting, it appears as if the
>>> qom-next commit "qbus: Make child devices links" [1] is causing
>>> assertions for both virtio-scsi and ahci but not for qemu-system-x86_64
>>> without parameters:
>>>
>>> $ x86_64-softmmu/qemu-system-x86_64 -enable-kvm -device
>>> virtio-scsi-pci,id=mcbus
>>> qemu-system-x86_64: /home/andreas/QEMU/qemu-rcar/memory.c:1259:
>>> memory_region_add_subregion_common: Assertion `!subregion->parent' failed.
>> 
>> A stack trace would be helpful,
> 
> $ gdb --ex run --args x86_64-softmmu/qemu-system-x86_64 -enable-kvm
> -device virtio-scsi-pci,id=mcbus
> [...]
> qemu-system-x86_64: /home/andreas/QEMU/qemu-rcar/memory.c:1259:
> memory_region_add_subregion_common: Assertion `!subregion->parent' failed.
> 
> Program received signal SIGABRT, Aborted.
> 0x00007ffff5769d95 in raise () from /lib64/libc.so.6
> (gdb) bt
> #0  0x00007ffff5769d95 in raise () from /lib64/libc.so.6
> #1  0x00007ffff576b2ab in abort () from /lib64/libc.so.6
> #2  0x00007ffff57628fe in __assert_fail_base () from /lib64/libc.so.6
> #3  0x00007ffff57629a2 in __assert_fail () from /lib64/libc.so.6
> #4  0x000055555576764c in memory_region_add_subregion_common (
>     mr=<optimized out>, offset=<optimized out>, subregion=<optimized out>)
>     at /home/andreas/QEMU/qemu-rcar/memory.c:1259
> #5  memory_region_add_subregion_common (mr=<optimized out>,
>     offset=<optimized out>, subregion=<optimized out>)
>     at /home/andreas/QEMU/qemu-rcar/memory.c:1253
> #6  0x000055555574203f in apic_init (apic_id=0 '\000', env=0x555556468d90)
>     at /home/andreas/QEMU/qemu-rcar/hw/i386/../pc.c:911
> #7  pc_new_cpu (cpu_model=0x55555583aec3 "qemu64")
>     at /home/andreas/QEMU/qemu-rcar/hw/i386/../pc.c:948
> #8  pc_cpus_init (cpu_model=0x55555583aec3 "qemu64")
>     at /home/andreas/QEMU/qemu-rcar/hw/i386/../pc.c:969
> #9  0x0000555555742d6c in pc_init1 (system_memory=0x5555564627b0, system_io=
>     0x555556462880, ram_size=134217728, boot_device=0x7fffffffdd50 "cad",
>     kernel_filename=0x0, kernel_cmdline=0x555555813c57 "", initrd_filename=
>     0x0, cpu_model=0x0, pci_enabled=1, kvmclock_enabled=1)
>     at /home/andreas/QEMU/qemu-rcar/hw/i386/../pc_piix.c:151
> #10 0x00005555557437c8 in pc_init_pci (ram_size=134217728, boot_device=
>     0x7fffffffdd50 "cad", kernel_filename=0x0, kernel_cmdline=
> ---Type <return> to continue, or q <return> to quit---
>     0x555555813c57 "", initrd_filename=0x0, cpu_model=<optimized out>)
>     at /home/andreas/QEMU/qemu-rcar/hw/i386/../pc_piix.c:296
> #11 0x00005555555c3429 in main (argc=<optimized out>, argv=<optimized out>,
>     envp=<optimized out>) at /home/andreas/QEMU/qemu-rcar/vl.c:3517
> 
>> as well as a printout of what
>> subregion->parent actually is.
> 
> (gdb) select-frame 4
> (gdb) print subregion->parent
> value has been optimized out
> 
> Any suggestion?

--enable-debug
or look for it in another frame
or both

> 
>> You can also run 'qemu mtree' from gdb after including scripts/qemu-gdb.py.
> 
> Unfortunately neither the script nor the commit introducing it nor
> Google offer any usage instructions...
> 
> (gdb) include
> Undefined command: "include".  Try "help".
> 
> (gdb) shell sh ../qemu-rcar/scripts/qemu-gdb.py
> ^C(gdb) Quit


(gdb) source /path/to/qemu/scripts/qemu-gdb.py
(gdb) qemu mtree

There is a facility to autoload those scripts, we should use it.

> 
> BTW if some write is going wrong somewhere then this symptom here could
> be just accidental. After all we don't seem to be changing any
> MemoryRegion in this commit.
> 

Right.  If subregion->parent points at garbage then this would prove it.

-- 
error compiling committee.c: too many arguments to function