Re: [Qemu-devel] [Spice-devel] Postcopy+spice crash

[Dr. David Alan Gilbert]

* Gerd Hoffmann (address@hidden) wrote:
>   Hi,
> 
> Yep, spice worker thread ...
> 
> > Thread 7 (Thread 0x7fbe7f9ff700 (LWP 22383)):
> > #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
> 
> ... busy processing post_load request from main thread ...
> 
> > Thread 1 (Thread 0x7fc0aead5c40 (LWP 22376)):
> > #0  0x00007fc0aa42f49d in read () from /lib64/libpthread.so.0
> > #1  0x00007fc0a8bf9264 in read_safe () from /lib64/libspice-server.so.1
> > #2  0x00007fc0a8bf9717 in dispatcher_send_message () from 
> > /lib64/libspice-server.so.1
> > #3  0x00007fc0a8bfa0c2 in red_dispatcher_loadvm_commands () from 
> > /lib64/libspice-server.so.1
> > #4  0x000055646556c03d in qxl_spice_loadvm_commands (address@hidden, 
> > address@hidden, count=2) at /root/git/qemu/hw/display/qxl.c:219
> > #5  0x000055646556d15f in qxl_post_load (opaque=0x55646755b8c0, 
> > version=<optimized out>) at /root/git/qemu/hw/display/qxl.c:2212
> > #6  0x000055646562f1b8 in vmstate_load_state (address@hidden, 
> > vmsd=<optimized out>, opaque=0x55646755b8c0, address@hidden) at 
> > /root/git/qemu/migration/vmstate.c:151
> > #7  0x000055646540f4a1 in vmstate_load (f=0x5564666347d0, 
> > se=0x5564676f90a0, version_id=21) at /root/git/qemu/migration/savevm.c:690
> > #8  0x000055646540f6db in qemu_loadvm_section_start_full (address@hidden, 
> > address@hidden) at /root/git/qemu/migration/savevm.c:1843
> > #9  0x000055646540f9ac in qemu_loadvm_state_main (address@hidden, 
> > address@hidden) at /root/git/qemu/migration/savevm.c:1900
> > #10 0x000055646540fd8f in loadvm_handle_cmd_packaged (mis=0x556466c93f10) 
> > at /root/git/qemu/migration/savevm.c:1660
> > #11 loadvm_process_command (f=0x556467e45740) at 
> > /root/git/qemu/migration/savevm.c:1723
> > #12 qemu_loadvm_state_main (address@hidden, address@hidden) at 
> > /root/git/qemu/migration/savevm.c:1913
> > #13 0x0000556465412546 in qemu_loadvm_state (address@hidden) at 
> > /root/git/qemu/migration/savevm.c:1973
> > #14 0x000055646562b4e8 in process_incoming_migration_co 
> > (opaque=0x556467e45740) at /root/git/qemu/migration/migration.c:394
> > #15 0x0000556465746ada in coroutine_trampoline (i0=<optimized out>, 
> > i1=<optimized out>) at /root/git/qemu/util/coroutine-ucontext.c:79
> > #16 0x00007fc0a60c7cf0 in ?? () from /lib64/libc.so.6
> > #17 0x00007ffe14885180 in ?? ()
> > #18 0x0000000000000000 in ?? ()
> 
> > It should; the device memory is just a RAMBlock that's migrated, so if it's
> > not arrived yet from the source the qxl code will block until postcopy
> > drags it across; assuming that is that the qxl code on the source isn't
> > still trying to write to it's copy at the same time, which at this
> > point it shouldn't.
> 
> Seems it happens while restoring the cursor,
> does this patch make a difference?

Hmm, my test case doesn't want to fail today, so unfortunately I can't tell.
(I've done at least 10 postcopies)

Dave

> --- a/hw/display/qxl.c
> +++ b/hw/display/qxl.c
> @@ -2238,12 +2238,14 @@ static int qxl_post_load(void *opaque, int
> version)
>              cmds[out].group_id = MEMSLOT_GROUP_GUEST;
>              out++;
>          }
> +#if 0
>          if (d->guest_cursor) {
>              cmds[out].cmd.data = d->guest_cursor;
>              cmds[out].cmd.type = QXL_CMD_CURSOR;
>              cmds[out].group_id = MEMSLOT_GROUP_GUEST;
>              out++;
>          }
> +#endif
>          qxl_spice_loadvm_commands(d, cmds, out);
>          g_free(cmds);
>          if (d->guest_monitors_config) {
> 
> cheers,
>   Gerd
> 
--
Dr. David Alan Gilbert / address@hidden / Manchester, UK