[Qemu-devel] [Bug 1711602] Re: --copy-storage-all failing with qemu 2.10

[ChristianEhrhardt]

Via a watchpoints I found that the error is set by qemu_fill_buffer.

b qemu_loadvm_state
handle SIGUSR1 nostop noprint pass
c
# on the break check and watch the status
(gdb) p f
$1 = (QEMUFile *) 0xb9babb3c00
(gdb) p *f
$2 = {ops = 0xb9b89880a0 <channel_input_ops>, hooks = 0x0, opaque = 
0xb9bbabfe00, bytes_xfer = 0, xfer_limit = 0, pos = 0, buf_index = 0, 
  buf_size = 0, buf = '\000' <repeats 32767 times>, may_free = {0}, iov = 
{{iov_base = 0x0, iov_len = 0} <repeats 64 times>}, iovcnt = 0, 
  last_error = 0}

# ok still no err, set watchpoint
(gdb) p &(f->last_error)
$4 = (int *) 0xb9babbc044
(gdb) watch *(int *) 0xb9babbc044
Hardware watchpoint 2: *(int *) 0xb9babbc044

# This catches the following
Thread 1 "qemu-system-x86" hit Hardware watchpoint 2: *(int *) 0xb9babbc044

Old value = 0
New value = -5
0x000000b9b82bd0ec in qemu_file_set_error (ret=-5, f=0xb9babb3c00) at 
./migration/qemu-file.c:125
warning: Source file is more recent than executable.
125             f->last_error = ret;
(gdb) bt
#0  0x000000b9b82bd0ec in qemu_file_set_error (ret=-5, f=0xb9babb3c00) at 
./migration/qemu-file.c:125
#1  qemu_fill_buffer (f=0xb9babb3c00) at ./migration/qemu-file.c:299
#2  0x000000b9b82bdbb1 in qemu_peek_byte (f=0xb9babb3c00, offset=0) at 
./migration/qemu-file.c:553
#3  0x000000b9b82bdc1b in qemu_get_byte (address@hidden) at 
./migration/qemu-file.c:566
#4  0x000000b9b82b5853 in qemu_loadvm_state_main (address@hidden, 
mis=0xb9b8a4f700 <mis_current>) at ./migration/savevm.c:1947
#5  0x000000b9b82b864f in qemu_loadvm_state (address@hidden) at 
./migration/savevm.c:2032
#6  0x000000b9b82af5c3 in process_incoming_migration_co (opaque=0xb9babb3c00) 
at ./migration/migration.c:320
#7  0x000000b9b83e42a6 in coroutine_trampoline (i0=<optimized out>, 
i1=<optimized out>) at ./util/coroutine-ucontext.c:79
#8  0x00007fbf3702fac0 in ?? () from /lib/x86_64-linux-gnu/libc.so.6
#9  0x00007fffe3f9f800 in ?? ()
#10 0x0000000000000000 in ?? ()

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https://bugs.launchpad.net/bugs/1711602

Title:
  --copy-storage-all failing with qemu 2.10

Status in QEMU:
  New
Status in libvirt package in Ubuntu:
  Confirmed
Status in qemu package in Ubuntu:
  Confirmed

Bug description:
  We fixed an issue around disk locking already in regard to qemu-nbd
  [1], but there still seem to be issues.

  $ virsh migrate --live --copy-storage-all kvmguest-artful-normal 
qemu+ssh://10.22.69.196/system
  error: internal error: qemu unexpectedly closed the monitor: 
2017-08-18T12:10:29.800397Z qemu-system-x86_64: -chardev pty,id=charserial0: 
char device redirected to /dev/pts/0 (label charserial0)
  2017-08-18T12:10:48.545776Z qemu-system-x86_64: load of migration failed: 
Input/output error

  Source libvirt log for the guest:
  2017-08-18 12:09:08.251+0000: initiating migration
  2017-08-18T12:09:08.809023Z qemu-system-x86_64: Unable to read from socket: 
Connection reset by peer
  2017-08-18T12:09:08.809481Z qemu-system-x86_64: Unable to read from socket: 
Connection reset by peer

  Target libvirt log for the guest:
  2017-08-18T12:09:08.730911Z qemu-system-x86_64: load of migration failed: 
Input/output error
  2017-08-18 12:09:09.010+0000: shutting down, reason=crashed

  Given the timing it seems that the actual copy now works (it is busy ~10 
seconds on my environment which would be the copy).
  Also we don't see the old errors we saw before, but afterwards on the actual 
take-over it fails.

  Dmesg has no related denials as often apparmor is in the mix.

  Need to check libvirt logs of source [2] and target [3] in Detail.

  [1]: https://lists.gnu.org/archive/html/qemu-devel/2017-08/msg02200.html
  [2]: http://paste.ubuntu.com/25339356/
  [3]: http://paste.ubuntu.com/25339358/

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