[Qemu-devel] [BUG] qemu-kvm: memory_region_add_subregion_common: Assertion `!subregion->parent' failed.

[Qemu-devel] [BUG] qemu-kvm: memory_region_add_subregion_common: Assertion `!subregion->parent' failed.

[Lai Jiangshan]

This bug is triggered for my Windows XP guest, but not for my linux guests.

The gdb result shows that a "vga.vram" memoryregion is added twice.

------------libvirt log -------

2011-10-25 16:18:58.117: starting up
LC_ALL=C PATH=/sbin:/usr/sbin:/bin:/usr/bin QEMU_AUDIO_DRV=none /home/laijs/bin/qemu.sh -S -M pc-0.13 -enable-kvm -m 256 -smp 1,sockets=1,cores=1,threads=1 -name Windows -uuid 3b0f4f29-1ca1-c199-a080-3ccac8f745a9 -nodefconfig -nodefaults -chardev socket,id=charmonitor,path=/var/lib/libvirt/qemu/Windows.monitor,server,nowait -mon chardev=charmonitor,id=monitor,mode=control -rtc base=localtime -no-shutdown -drive file=/home/laijs/Windows/windows.img,if=none,id=drive-ide0-0-0,format=qcow2,cache=none -device ide-drive,bus=ide.0,unit=0,drive=drive-ide0-0-0,id=ide0-0-0,bootindex=1 -drive file=/home/laijs/OFFICE2003_STD_EN.ISO,if=none,media=cdrom,id=drive-ide0-1-0,readonly=on,format=raw -device ide-drive,bus=ide.1,unit=0,drive=drive-ide0-1-0,id=ide0-1-0 -netdev tap,fd=17,id=hostnet0 -device pcnet,netdev=hostnet0,id=net0,mac=52:54:00:a5:d2:ea,bus=pci.0,multifunction=on,addr=0x3.0x0 -usb -vnc 127.0.0.1:0 -vga std -device virtio-balloon-pci,id=balloon0,bus=pci.0,multifunction=on,addr=0
x5.0x0
Domain id=45 is tainted: high-privileges
qemu-system-x86_64: /home/laijs/work/qemu-kvm/memory.c:1083: memory_region_add_subregion_common: Assertion `!subregion->parent' failed.
2011-10-25 16:18:58.380: shutting down



-------------git bisect result





b195043003d90ea4027ea01cc7a6c974ac915108 is the first bad commit
commit b195043003d90ea4027ea01cc7a6c974ac915108
Author: Avi Kivity <avi@redhat.com>
Date:   Mon Aug 8 16:08:57 2011 +0300

    vga: convert vga and its derivatives to the memory API
    
    Convert all vga memory to the memory API.  Note we need to fall back to
    get_system_memory(), since the various buses don't pass the vga window
    as a memory region.
    
    We no longer need to sync the dirty bitmap of the cirrus mapped memory
    banks, since the memory API takes care of that for us.
    
    [jan: fix vga-pci logging]
    
    Reviewed-by: Richard Henderson <rth@twiddle.net>
    Signed-off-by: Avi Kivity <avi@redhat.com>
    Signed-off-by: Anthony Liguori <aliguori@us.ibm.com>

:040000 040000 e8faf8e539a4ec814ef212ce97040046363a67f3 917701ddf6a42f49204a5b2adfa9654c03c0d6f6 M	hw

-----------------------gdb result(b19504300)--------


(gdb) bt
#0  0x000000000042995a in memory_region_add_subregion_common (mr=0x2a799a0, offset=4026531840, 
    subregion=0x2d17250) at /home/laijs/work/qemu-kvm/memory.c:1083
#1  0x0000000000590408 in pci_update_mappings (d=0x2d16f40)
    at /home/laijs/work/qemu-kvm/hw/pci.c:1123
#2  0x0000000000590846 in pci_default_write_config (d=0x2d16f40, addr=4, 
    val=<value optimized out>, l=<value optimized out>) at /home/laijs/work/qemu-kvm/hw/pci.c:1173
#3  0x0000000000427616 in kvm_handle_io (env=0x2bdf500) at /home/laijs/work/qemu-kvm/kvm-all.c:837
#4  kvm_cpu_exec (env=0x2bdf500) at /home/laijs/work/qemu-kvm/kvm-all.c:976
#5  0x000000000040c308 in cpu_exec_all () at /home/laijs/work/qemu-kvm/cpus.c:1102
#6  0x0000000000587281 in main_loop (argc=<value optimized out>, argv=<value optimized out>, 
    envp=<value optimized out>) at /home/laijs/work/qemu-kvm/vl.c:1392
#7  main (argc=<value optimized out>, argv=<value optimized out>, envp=<value optimized out>)
    at /home/laijs/work/qemu-kvm/vl.c:3356
(gdb) p mr->name
$1 = 0x2a79a70 "system"
(gdb) p subregion->name
$2 = 0x2c02960 "vga.vram"
(gdb) p *subregion
$3 = {ops = 0x0, opaque = 0x0, parent = 0x2a799a0, size = 8388608, addr = 3758096384, offset = 0, 
  backend_registered = true, ram_addr = 268697600, iorange = {ops = 0x0, base = 0, len = 0}, 
  terminates = true, alias = 0x0, alias_offset = 0, priority = 1, may_overlap = true, subregions = 
    {tqh_first = 0x0, tqh_last = 0x2d172c8}, subregions_link = {tqe_next = 0x2b7d610, tqe_prev = 
    0x2b7d788}, coalesced = {tqh_first = 0x0, tqh_last = 0x2d172e8}, name = 0x2c02960 "vga.vram", 
  dirty_log_mask = 1 '\001', ioeventfd_nb = 0, ioeventfds = 0x0}
(gdb) p subregion->parent
$4 = (MemoryRegion *) 0x2a799a0
(gdb) p *subregion->parent
$5 = {ops = 0x0, opaque = 0x0, parent = 0x0, size = 9223372036854775807, addr = 0, offset = 0, 
  backend_registered = false, ram_addr = 0, iorange = {ops = 0x0, base = 0, len = 0}, terminates = 
    false, alias = 0x0, alias_offset = 0, priority = 0, may_overlap = false, subregions = {
    tqh_first = 0x2acc120, tqh_last = 0x2b4d168}, subregions_link = {tqe_next = 0x0, tqe_prev = 
    0x0}, coalesced = {tqh_first = 0x0, tqh_last = 0x2a79a38}, name = 0x2a79a70 "system", 
  dirty_log_mask = 0 '\000', ioeventfd_nb = 0, ioeventfds = 0x0}

Re: [Qemu-devel] [BUG] qemu-kvm: memory_region_add_subregion_common: Assertion `!subregion->parent' failed.

[Jan Kiszka]

On 2011-10-25 11:42, Lai Jiangshan wrote:
> This bug is triggered for my Windows XP guest, but not for my linux guests.
> 
> The gdb result shows that a "vga.vram" memoryregion is added twice.
> 
> ------------libvirt log -------
> 
> 2011-10-25 16:18:58.117: starting up
> LC_ALL=C PATH=/sbin:/usr/sbin:/bin:/usr/bin QEMU_AUDIO_DRV=none /home/laijs/bin/qemu.sh -S -M pc-0.13 -enable-kvm -m 256 -smp 1,sockets=1,cores=1,threads=1 -name Windows -uuid 3b0f4f29-1ca1-c199-a080-3ccac8f745a9 -nodefconfig -nodefaults -chardev socket,id=charmonitor,path=/var/lib/libvirt/qemu/Windows.monitor,server,nowait -mon chardev=charmonitor,id=monitor,mode=control -rtc base=localtime -no-shutdown -drive file=/home/laijs/Windows/windows.img,if=none,id=drive-ide0-0-0,format=qcow2,cache=none -device ide-drive,bus=ide.0,unit=0,drive=drive-ide0-0-0,id=ide0-0-0,bootindex=1 -drive file=/home/laijs/OFFICE2003_STD_EN.ISO,if=none,media=cdrom,id=drive-ide0-1-0,readonly=on,format=raw -device ide-drive,bus=ide.1,unit=0,drive=drive-ide0-1-0,id=ide0-1-0 -netdev tap,fd=17,id=hostnet0 -device pcnet
>  ,netdev=hostnet0,id=net0,mac=52:54:00:a5:d2:ea,bus=pci.0,multifunction=on,addr=0x3.0x0 -usb -vnc 127.0.0.1:0 -vga std -device virtio-balloon-pci,id=balloon0,bus=pci.0,multifunction=on,addr=0
> x5.0x0
> Domain id=45 is tainted: high-privileges
> qemu-system-x86_64: /home/laijs/work/qemu-kvm/memory.c:1083: memory_region_add_subregion_common: Assertion `!subregion->parent' failed.
> 2011-10-25 16:18:58.380: shutting down
> 
> 
> 
> -------------git bisect result
> 
> 
> 
> 
> 
> b195043003d90ea4027ea01cc7a6c974ac915108 is the first bad commit
> commit b195043003d90ea4027ea01cc7a6c974ac915108
> Author: Avi Kivity <avi@redhat.com>
> Date:   Mon Aug 8 16:08:57 2011 +0300
> 
>     vga: convert vga and its derivatives to the memory API
>     
>     Convert all vga memory to the memory API.  Note we need to fall back to
>     get_system_memory(), since the various buses don't pass the vga window
>     as a memory region.
>     
>     We no longer need to sync the dirty bitmap of the cirrus mapped memory
>     banks, since the memory API takes care of that for us.
>     
>     [jan: fix vga-pci logging]
>     
>     Reviewed-by: Richard Henderson <rth@twiddle.net>
>     Signed-off-by: Avi Kivity <avi@redhat.com>
>     Signed-off-by: Anthony Liguori <aliguori@us.ibm.com>
> 
> :040000 040000 e8faf8e539a4ec814ef212ce97040046363a67f3 917701ddf6a42f49204a5b2adfa9654c03c0d6f6 M	hw
> 
> -----------------------gdb result(b19504300)--------
> 
> 
> (gdb) bt
> #0  0x000000000042995a in memory_region_add_subregion_common (mr=0x2a799a0, offset=4026531840, 
>     subregion=0x2d17250) at /home/laijs/work/qemu-kvm/memory.c:1083
> #1  0x0000000000590408 in pci_update_mappings (d=0x2d16f40)
>     at /home/laijs/work/qemu-kvm/hw/pci.c:1123
> #2  0x0000000000590846 in pci_default_write_config (d=0x2d16f40, addr=4, 
>     val=<value optimized out>, l=<value optimized out>) at /home/laijs/work/qemu-kvm/hw/pci.c:1173
> #3  0x0000000000427616 in kvm_handle_io (env=0x2bdf500) at /home/laijs/work/qemu-kvm/kvm-all.c:837
> #4  kvm_cpu_exec (env=0x2bdf500) at /home/laijs/work/qemu-kvm/kvm-all.c:976
> #5  0x000000000040c308 in cpu_exec_all () at /home/laijs/work/qemu-kvm/cpus.c:1102
> #6  0x0000000000587281 in main_loop (argc=<value optimized out>, argv=<value optimized out>, 
>     envp=<value optimized out>) at /home/laijs/work/qemu-kvm/vl.c:1392
> #7  main (argc=<value optimized out>, argv=<value optimized out>, envp=<value optimized out>)
>     at /home/laijs/work/qemu-kvm/vl.c:3356
> (gdb) p mr->name
> $1 = 0x2a79a70 "system"
> (gdb) p subregion->name
> $2 = 0x2c02960 "vga.vram"
> (gdb) p *subregion
> $3 = {ops = 0x0, opaque = 0x0, parent = 0x2a799a0, size = 8388608, addr = 3758096384, offset = 0, 
>   backend_registered = true, ram_addr = 268697600, iorange = {ops = 0x0, base = 0, len = 0}, 
>   terminates = true, alias = 0x0, alias_offset = 0, priority = 1, may_overlap = true, subregions = 
>     {tqh_first = 0x0, tqh_last = 0x2d172c8}, subregions_link = {tqe_next = 0x2b7d610, tqe_prev = 
>     0x2b7d788}, coalesced = {tqh_first = 0x0, tqh_last = 0x2d172e8}, name = 0x2c02960 "vga.vram", 
>   dirty_log_mask = 1 '\001', ioeventfd_nb = 0, ioeventfds = 0x0}
> (gdb) p subregion->parent
> $4 = (MemoryRegion *) 0x2a799a0
> (gdb) p *subregion->parent
> $5 = {ops = 0x0, opaque = 0x0, parent = 0x0, size = 9223372036854775807, addr = 0, offset = 0, 
>   backend_registered = false, ram_addr = 0, iorange = {ops = 0x0, base = 0, len = 0}, terminates = 
>     false, alias = 0x0, alias_offset = 0, priority = 0, may_overlap = false, subregions = {
>     tqh_first = 0x2acc120, tqh_last = 0x2b4d168}, subregions_link = {tqe_next = 0x0, tqe_prev = 
>     0x0}, coalesced = {tqh_first = 0x0, tqh_last = 0x2a79a38}, name = 0x2a79a70 "system", 
>   dirty_log_mask = 0 '\000', ioeventfd_nb = 0, ioeventfds = 0x0}
> 

That's likely vga_init_vbe vs. pci_register_bar with vga.vram. Either
the PCI bar or the VBE mapping should be wrapped by an alias region
pointing to the original vram. And vmware_vga seems to be affected as well.

Jan

-- 
Siemens AG, Corporate Technology, CT T DE IT 1
Corporate Competence Center Embedded Linux

Re: [Qemu-devel] [BUG] qemu-kvm: memory_region_add_subregion_common: Assertion `!subregion->parent' failed.

[Gerd Hoffmann]

  Hi,

>> -M pc-0.13

> That's likely vga_init_vbe vs. pci_register_bar with vga.vram. Either
> the PCI bar or the VBE mapping should be wrapped by an alias region
> pointing to the original vram. And vmware_vga seems to be affected as well.

Will there be a migration flag day before 1.0?
If yes we can just zap the bochs vbe mapping for pci vga cards.

It is not used any more since 0.14 and it is only there for migration
compatibility with 0.13 and older ...

Easiest way around this is to use a more recent machine type.

cheers,
  Gerd