* Christian Borntraeger (borntrae...@de.ibm.com) wrote: > On 04/24/2017 12:53 PM, Dr. David Alan Gilbert wrote: > > * Christian Borntraeger (borntrae...@de.ibm.com) wrote: > >> David, Juan, > >> > >> I can trigger a hang of postcopy migration (when I do it early) so > >> that both sides are in paused state. Looks like one thread is still > >> loading vmstates for virtio and this load accesses guest memory and > >> triggers a userfault. > > > > It's perfectly legal for the destination to cause a userfault as it > > loads the virtio queue - the virtio queue should be being loaded by > > the main thread from the buffer while the 'listening' thread is > > waiting for the incoming page data. > > > > Can you turn on the following tracing please: destination: > > postcopy_ram_fault_thread_request postcopy_place_page > > postcopy_place_page_zero > > > > source: migrate_handle_rp_req_pages ram_save_queue_pages > > > > You should see: virtio does the access userfault generates a fault > > postcopy_ram_fault_thread_request sends the request to the source > > > > the source sees migrate_handle_rp_req_pages queues it with > > ram_save_queue_pages > > > > the destination sees the page arrive and postcopy_place_page or > > postcopy_place_page_zero > > > > some of that might disappear if the page was already on it's way. > > > the last event on the source are > [..] > 58412@1493037953.747988:postcopy_place_page host=0x3ff92246000 > 58412@1493037953.747992:postcopy_place_page host=0x3ff92247000
How do you see those on the source??? > 58412@1493037956.804210:migrate_handle_rp_req_pages in s390.ram at 41d9000 > len 1000 > 58412@1493037956.804216:ram_save_queue_pages s390.ram: start: 41d9000 len: 100 > Is that a typo? I'm expecting those two 'len' fields to be the same? > On the target a see lots of > > 39741@1493037958.833710:postcopy_place_page_zero host=0x3ff9befa000 > 39741@1493037958.833716:postcopy_place_page host=0x3ff9befb000 > 39741@1493037958.833759:postcopy_place_page host=0x3ff9befc000 > 39741@1493037958.833818:postcopy_place_page host=0x3ff9befd000 > 39741@1493037958.833819:postcopy_place_page_zero host=0x3ff9befe000 > 39741@1493037958.833822:postcopy_place_page host=0x3ff9beff000 > > So we have about 2 seconds of traffic going on after that request, > I assume its precopy related. > > Looking back on the target history there was > 39741@1493037956.804337:postcopy_ram_fault_thread_request Request for > HVA=3ff618d9000 rb=s390.ram offset=41d9000 > > In fact it seems to be the first and only request: > > # cat /tmp/test0.trace | grep -v postcopy_place_page > > 39741@1493037956.804337:postcopy_ram_fault_thread_request Request for > HVA=3ff618d9000 rb=s390.ram offset=41d9000 OK, does the HVA there correspond to the address that your virtio device is blocking on? (or at least the start of the page) Do you see a postcopy_place_page with a host= the same HVA ? From the source backtrace, I think the source thinks it's sent everything and is waiting for the return-path-thread to close. Dave > > > > Dave > > > >> Thread 1 (Thread 0x3ffa2f45f00 (LWP 21122)): #0 0x0000000001017130 > >> in lduw_he_p (ptr=0x3ff498d9002) at > >> /root/qemu/include/qemu/bswap.h:317 <---- according to the host > >> kernel this threads hangs in handle_userfault. #1 > >> 0x0000000001017342 in lduw_le_p (ptr=0x3ff498d9002) at > >> /root/qemu/include/qemu/bswap.h:359 #2 0x0000000001025840 in > >> address_space_lduw_internal_cached (cache=0x283491d0, addr=2, > >> attrs=..., result=0x0, endian=DEVICE_LITTLE_ENDIAN) at > >> /root/qemu/memory_ldst.inc.c:284 #3 0x00000000010259a6 in > >> address_space_lduw_le_cached (cache=0x283491d0, addr=2, attrs=..., > >> result=0x0) at /root/qemu/memory_ldst.inc.c:315 #4 > >> 0x0000000001025ad6 in lduw_le_phys_cached (cache=0x283491d0, > >> addr=2) at /root/qemu/memory_ldst.inc.c:334 #5 0x0000000001116c10 > >> in virtio_lduw_phys_cached (vdev=0x28275090, cache=0x283491d0, > >> pa=2) at /root/qemu/include/hw/virtio/virtio-access.h:166 #6 > >> 0x0000000001117940 in vring_used_idx (vq=0x3ffa2e1c090) at > >> /root/qemu/hw/virtio/virtio.c:263 #7 0x000000000111daea in > >> virtio_load (vdev=0x28275090, f=0x28353600, version_id=2) at > >> /root/qemu/hw/virtio/virtio.c:2168 #8 0x000000000111d0cc in > >> virtio_device_get (f=0x28353600, opaque=0x28275090, size=0, > >> field=0x16adf38 <__compound_literal.0>) at > >> /root/qemu/hw/virtio/virtio.c:1975 #9 0x00000000012a7f50 in > >> vmstate_load_state (f=0x28353600, vmsd=0x14db480 > >> <vmstate_virtio_blk>, opaque=0x28275090, version_id=2) at > >> /root/qemu/migration/vmstate.c:128 #10 0x00000000010cbc08 in > >> vmstate_load (f=0x28353600, se=0x28279e60, version_id=2) at > >> /root/qemu/migration/savevm.c:732 #11 0x00000000010ced6e in > >> qemu_loadvm_section_start_full (f=0x28353600, mis=0x17169a8 > >> <mis_current>) at /root/qemu/migration/savevm.c:1890 #12 > >> 0x00000000010cf00c in qemu_loadvm_state_main (f=0x28353600, > >> mis=0x17169a8 <mis_current>) at /root/qemu/migration/savevm.c:1947 > >> #13 0x00000000010ce5bc in loadvm_handle_cmd_packaged (mis=0x17169a8 > >> <mis_current>) at /root/qemu/migration/savevm.c:1707 #14 > >> 0x00000000010ce87e in loadvm_process_command (f=0x282c7d20) at > >> /root/qemu/migration/savevm.c:1770 #15 0x00000000010cf056 in > >> qemu_loadvm_state_main (f=0x282c7d20, mis=0x17169a8 <mis_current>) > >> at /root/qemu/migration/savevm.c:1960 #16 0x00000000010cf2b6 in > >> qemu_loadvm_state (f=0x282c7d20) at > >> /root/qemu/migration/savevm.c:2020 #17 0x000000000129d234 in > >> process_incoming_migration_co (opaque=0x282c7d20) at > >> /root/qemu/migration/migration.c:404 #18 0x00000000014b6ca2 in > >> coroutine_trampoline (i0=0, i1=674533168) at > >> /root/qemu/util/coroutine-ucontext.c:79 #19 0x000003ff8de530ea in > >> __makecontext_ret () from target:/lib64/libc.so.6 > >> > >> Thread 8 (Thread 0x3ff40b38910 (LWP 21165)): #0 0x000003ff8df04336 > >> in syscall () from target:/lib64/libc.so.6 #1 0x00000000014933ce > >> in qemu_futex_wait (f=0x17169b0 <mis_current+8>, val=4294967295) at > >> /root/qemu/include/qemu/futex.h:26 #2 0x00000000014935d0 in > >> qemu_event_wait (ev=0x17169b0 <mis_current+8>) at > >> /root/qemu/util/qemu-thread-posix.c:399 #3 0x00000000010ce094 in > >> postcopy_ram_listen_thread (opaque=0x282c7d20) at > >> /root/qemu/migration/savevm.c:1532 #4 0x000003ff8e007bc4 in > >> start_thread () from target:/lib64/libpthread.so.0 #5 > >> 0x000003ff8df0a9f2 in thread_start () from target:/lib64/libc.so.6 > >> > >> Thread 7 (Thread 0x3ff41338910 (LWP 21164)): #0 0x000003ff8defd72c > >> in ?? () from target:/lib64/libc.so.6 #1 0x00000000012af920 in > >> postcopy_ram_fault_thread (opaque=0x17169a8 <mis_current>) at > >> /root/qemu/migration/postcopy-ram.c:437 #2 0x000003ff8e007bc4 in > >> start_thread () from target:/lib64/libpthread.so.0 #3 > >> 0x000003ff8df0a9f2 in thread_start () from target:/lib64/libc.so.6 > >> > >> Thread 6 (Thread 0x3ff41b38910 (LWP 21163)): #0 0x000003ff8e00d450 > >> in pthread_cond_wait@@GLIBC_2.3.2 () from > >> target:/lib64/libpthread.so.0 #1 0x0000000001492d66 in > >> qemu_cond_wait (cond=0x28302408, mutex=0x283023e0) at > >> /root/qemu/util/qemu-thread-posix.c:133 #2 0x00000000010c6080 in > >> do_data_decompress (opaque=0x283023d8) at > >> /root/qemu/migration/ram.c:2277 #3 0x000003ff8e007bc4 in > >> start_thread () from target:/lib64/libpthread.so.0 #4 > >> 0x000003ff8df0a9f2 in thread_start () from target:/lib64/libc.so.6 > >> > >> Thread 5 (Thread 0x3ff42338910 (LWP 21162)): #0 0x000003ff8e00d450 > >> in pthread_cond_wait@@GLIBC_2.3.2 () from > >> target:/lib64/libpthread.so.0 #1 0x0000000001492d66 in > >> qemu_cond_wait (cond=0x28302390, mutex=0x28302368) at > >> /root/qemu/util/qemu-thread-posix.c:133 #2 0x00000000010c6080 in > >> do_data_decompress (opaque=0x28302360) at > >> /root/qemu/migration/ram.c:2277 #3 0x000003ff8e007bc4 in > >> start_thread () from target:/lib64/libpthread.so.0 #4 > >> 0x000003ff8df0a9f2 in thread_start () from target:/lib64/libc.so.6 > >> > >> Thread 4 (Thread 0x3ff89287910 (LWP 21148)): #0 0x000003ff8e010abc > >> in __lll_lock_wait () from target:/lib64/libpthread.so.0 #1 > >> 0x000003ff8e00bcb6 in __pthread_mutex_cond_lock () from > >> target:/lib64/libpthread.so.0 #2 0x000003ff8e00d4ee in > >> pthread_cond_wait@@GLIBC_2.3.2 () from > >> target:/lib64/libpthread.so.0 #3 0x0000000001492d66 in > >> qemu_cond_wait (cond=0x2831eb00, mutex=0x1711688 > >> <qemu_global_mutex>) at /root/qemu/util/qemu-thread-posix.c:133 #4 > >> 0x000000000107720e in qemu_kvm_wait_io_event (cpu=0x282e09b0) at > >> /root/qemu/cpus.c:1085 #5 0x00000000010773aa in > >> qemu_kvm_cpu_thread_fn (arg=0x282e09b0) at /root/qemu/cpus.c:1123 > >> #6 0x000003ff8e007bc4 in start_thread () from > >> target:/lib64/libpthread.so.0 #7 0x000003ff8df0a9f2 in > >> thread_start () from target:/lib64/libc.so.6 > >> > >> Thread 3 (Thread 0x3ff8a7ff910 (LWP 21145)): #0 0x000003ff8defd832 > >> in ppoll () from target:/lib64/libc.so.6 #1 0x000000000148b092 in > >> qemu_poll_ns (fds=0x3ff840008c0, nfds=1, timeout=-1) at > >> /root/qemu/util/qemu-timer.c:322 #2 0x000000000148f46a in aio_poll > >> (ctx=0x2827e7b0, blocking=true) at /root/qemu/util/aio-posix.c:622 > >> #3 0x00000000011a78f6 in iothread_run (opaque=0x2827d740) at > >> /root/qemu/iothread.c:59 #4 0x000003ff8e007bc4 in start_thread () > >> from target:/lib64/libpthread.so.0 #5 0x000003ff8df0a9f2 in > >> thread_start () from target:/lib64/libc.so.6 > >> > >> Thread 2 (Thread 0x3ff8afff910 (LWP 21142)): #0 0x000003ff8df04336 > >> in syscall () from target:/lib64/libc.so.6 #1 0x00000000014933ce > >> in qemu_futex_wait (f=0x1b2b9b4 <rcu_call_ready_event>, > >> val=4294967295) at /root/qemu/include/qemu/futex.h:26 #2 > >> 0x00000000014935d0 in qemu_event_wait (ev=0x1b2b9b4 > >> <rcu_call_ready_event>) at /root/qemu/util/qemu-thread-posix.c:399 > >> #3 0x00000000014b3e40 in call_rcu_thread (opaque=0x0) at > >> /root/qemu/util/rcu.c:249 #4 0x000003ff8e007bc4 in start_thread () > >> from target:/lib64/libpthread.so.0 #5 0x000003ff8df0a9f2 in > >> thread_start () from target:/lib64/libc.so.6 > >> > >> > >> Looks like that this <qemu:arg value='-drive'/> <qemu:arg > >> value='driver=null-aio,id=null1,if=none,size=100G'/> <qemu:arg > >> value='-device'/> <qemu:arg > >> value='virtio-blk-ccw,scsi=off,drive=null1,serial=null1,num-queues=4'/> > >> > >> > >> is necessary to trigger the hang, with nun-qeues=1 everything seems to > >> work fine, so it might > >> be a virtio issue after all? > >> > >> Any idea? > >> > > -- Dr. David Alan Gilbert / dgilb...@redhat.com / Manchester, UK > > > -- Dr. David Alan Gilbert / dgilb...@redhat.com / Manchester, UK
