Re: [Qemu-devel] Postcopy+spice crash

["Dr. David Alan Gilbert" <dgilbert@redhat.com>]

* Gerd Hoffmann (kraxel@redhat.com) wrote:
> On Fr, 2016-12-02 at 17:44 +0000, Dr. David Alan Gilbert wrote:
> > Hi Gerd,
> >   I've got a moderately repeatable crash with spice playing
> > a video + postcopy.  Some of the time I just get a warning
> > (that I also get in precopy) but sometimes it turns into
> > a backtrace;
> > 
> > This is:
> >   f24 guest playing youtube fullscreen.
> >   migration between 2.7.0<->current head (had crash both ways)
> > 
> > The warning I get with precopy most of the time is:
> >   ./x86_64-softmmu/qemu-system-x86_64:26921): Spice-Warning **: red_memslots.c:94:validate_virt: virtual address out of range
> 
> That is in spice-server.  Which version do you run?

From the bottom of the post; spice-server-devel-0.12.4-19.el7.x86_64 (rhel 7)

> Adding spice-devel to Cc:
> 
> >     virt=0x7f5397ed002a+0x2925ff31 slot_id=1 group_id=1
> >     slot=0x7f5397c00000-0x7f539bbfe000 delta=0x7f5397c00000
> 
> Base address looks sane.
> Size (0x2925ff31) is bogous.
> 
> On a quick glance I'd blame the guest for sending corrupted commands.
> Strange though that it happens on migration only, so there could be
> a host issue too.  Or a timing issue triggered by migration.
> 
> Which migration phase?

This is the point at which it switches over in postcopy.

> Do you have seamless spice migration enabled?
> If so: Does it still reproduce with seamless migration turned off?

No I don't think so; I think the command line I was running was:
./x86_64-softmmu/qemu-system-x86_64 -vnc :0 -M pc-i440fx-2.7,accel=kvm -monitor stdio -netdev user,id=unet,hostfwd=tcp::2022-:22,hostfwd=tcp::2023-:2022 -device virtio-net-pci,netdev=unet -drive file=/home/vms/f24.qcow2,cache=none,id=disk,if=none  -device virtio-blk-pci,drive=disk -device virtio-balloon -vga qxl -device ich9-usb-ehci1 -device usb-tablet,id=in0 -device virtio-rng-pci -device AC97 -m 8192 -smp 4 -drive file=/home/vms/Fedora-Server-netinst-x86_64-23.iso,cache=none,id=cd,if=scsi -incoming tcp::4444

> > The crash I've had with postcopy is:
> > red_dispatcher_loadvm_commands:
> > id 0, group 0, virt start 0, virt end ffffffffffffffff, generation 0, delta 0
> > id 1, group 1, virt start 7fbe83c00000, virt end 7fbe87bfe000, generation 0, delta 7fbe83c00000
> > id 2, group 1, virt start 7fbe7fa00000, virt end 7fbe83a00000, generation 0, delta 7fbe7fa00000
> > (./x86_64-softmmu/qemu-system-x86_64:22376): Spice-CRITICAL **: red_memslots.c:123:get_virt: slot_id 128 too big, addr=8000000000000000
> > 
> > #0  0x00007fc0aa42f49d in read () from /lib64/libpthread.so.0
> > #1  0x00007fc0a8c36c01 in spice_backtrace_gstack () from /lib64/libspice-server.so.1
> > #2  0x00007fc0a8c3e4f7 in spice_logv () from /lib64/libspice-server.so.1
> > #3  0x00007fc0a8c3e655 in spice_log () from /lib64/libspice-server.so.1
> > #4  0x00007fc0a8bfc6de in get_virt () from /lib64/libspice-server.so.1
> > #5  0x00007fc0a8bfcb73 in red_get_data_chunks_ptr () from /lib64/libspice-server.so.1
> > #6  0x00007fc0a8bff3fa in red_get_cursor_cmd () from /lib64/libspice-server.so.1
> > #7  0x00007fc0a8c0fd79 in handle_dev_loadvm_commands () from /lib64/libspice-server.so.1
> > #8  0x00007fc0a8bf9523 in dispatcher_handle_recv_read () from /lib64/libspice-server.so.1
> > #9  0x00007fc0a8c1d5a5 in red_worker_main () from /lib64/libspice-server.so.1
> > #10 0x00007fc0aa428dc5 in start_thread () from /lib64/libpthread.so.0
> > #11 0x00007fc0a61786ed in clone () from /lib64/libc.so.6
> 
> Spice worker thread ...
> 
> > red_dispatcher_loadvm_commands:
> > id 0, group 0, virt start 0, virt end ffffffffffffffff, generation 0, delta 0
> > id 1, group 1, virt start 7f3b93800000, virt end 7f3b977fe000, generation 0, delta 7f3b93800000
> > id 2, group 1, virt start 7f3b8f400000, virt end 7f3b93400000, generation 0, delta 7f3b8f400000
> > (/opt/qemu/v2.7.0/bin/qemu-system-x86_64:41053): Spice-CRITICAL **: red_memslots.c:123:get_virt: slot_id 80 too big, addr=5000000000000000
> 
> 
> ... trying to decode a invalid qxl address.

Yes one observation is that I think a few (all?) of the bad
addresses I've seen there have been a single nybble followed by
a lot of 0's.

> > I'm using:
> > spice-server-devel-0.12.4-19.el7.x86_64
> 
> Ah, RHEL-7.3 host.
> 
> cheers,
>   Gerd
> 

Dave

--
Dr. David Alan Gilbert / dgilbert@redhat.com / Manchester, UK