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Re: [qemu-s390x] [Qemu-devel] [BUG] I/O thread segfault for QEMU on s390


From: Farhan Ali
Subject: Re: [qemu-s390x] [Qemu-devel] [BUG] I/O thread segfault for QEMU on s390x
Date: Fri, 2 Mar 2018 10:30:57 -0500
User-agent: Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.4.0



On 03/02/2018 04:23 AM, Stefan Hajnoczi wrote:
On Thu, Mar 01, 2018 at 09:33:35AM -0500, Farhan Ali wrote:
Hi,

I have been noticing some segfaults for QEMU on s390x, and I have been
hitting this issue quite reliably (at least once in 10 runs of a test case).
The qemu version is 2.11.50, and I have systemd created coredumps
when this happens.

Here is a back trace of the segfaulting thread:
The backtrace looks normal.

Please post the QEMU command-line and the details of the segfault (which
memory access faulted?).



I was able to create another crash today and here is the qemu comand line

/usr/bin/qemu-kvm -name guest=sles,debug-threads=on \
-S -object secret,id=masterKey0,format=raw,file=/var/lib/libvirt/qemu/domain-2-sles/master-key.aes \
-machine s390-ccw-virtio-2.12,accel=kvm,usb=off,dump-guest-core=off \
-m 4096 -realtime mlock=off -smp 8,sockets=8,cores=1,threads=1 \
-object iothread,id=iothread1 -object iothread,id=iothread2 -uuid b83a596b-3a1a-4ac9-9f3e-d9a4032ee52c \ -display none -no-user-config -nodefaults -chardev socket,id=charmonitor,path=/var/lib/libvirt/qemu/domain-2-sles/monitor.sock,server,nowait -mon chardev=charmonitor,id=monitor,mode=control -rtc base=utc -no-shutdown \ -boot strict=on -drive file=/dev/mapper/360050763998b0883980000002400002b,format=raw,if=none,id=drive-virtio-disk0,cache=none,aio=native -device virtio-blk-ccw,iothread=iothread1,scsi=off,devno=fe.0.0001,drive=drive-virtio-disk0,id=virtio-disk0,bootindex=1 -drive file=/dev/mapper/360050763998b0883980000002800002f,format=raw,if=none,id=drive-virtio-disk1,cache=none,aio=native -device virtio-blk-ccw,iothread=iothread2,scsi=off,devno=fe.0.0002,drive=drive-virtio-disk1,id=virtio-disk1 -netdev tap,fd=24,id=hostnet0,vhost=on,vhostfd=26 -device virtio-net-ccw,netdev=hostnet0,id=net0,mac=02:38:a6:36:e8:1f,devno=fe.0.0000 -chardev pty,id=charconsole0 -device sclpconsole,chardev=charconsole0,id=console0 -device virtio-balloon-ccw,id=balloon0,devno=fe.3.ffba -msg timestamp=on


This the latest back trace on the segfaulting thread, and it seems to segfault in swapcontext.

Program terminated with signal SIGSEGV, Segmentation fault.
#0  0x000003ff8595202c in swapcontext () from /lib64/libc.so.6


This is the remaining back trace:

#0  0x000003ff8595202c in swapcontext () from /lib64/libc.so.6
#1 0x000002aa33b45566 in qemu_coroutine_new () at util/coroutine-ucontext.c:164 #2 0x000002aa33b43eac in qemu_coroutine_create (address@hidden <blk_aio_write_entry>, address@hidden) at util/qemu-coroutine.c:76 #3 0x000002aa33a954da in blk_aio_prwv (blk=0x2aa4f0efda0, offset=<optimized out>, bytes=<optimized out>, qiov=0x3ff74019080, address@hidden <blk_aio_write_entry>, flags=0, cb=0x2aa338c62e8 <virtio_blk_rw_complete>, opaque=0x3ff74019020) at block/block-backend.c:1299 #4 0x000002aa33a9563e in blk_aio_pwritev (blk=<optimized out>, offset=<optimized out>, qiov=<optimized out>, flags=<optimized out>, cb=<optimized out>, opaque=0x3ff74019020) at block/block-backend.c:1400 #5 0x000002aa338c6a38 in submit_requests (niov=<optimized out>, num_reqs=1, start=<optimized out>, mrb=0x3ff831fe6e0, blk=<optimized out>) at /usr/src/debug/qemu-2.11.50/hw/block/virtio-blk.c:369 #6 virtio_blk_submit_multireq (blk=<optimized out>, address@hidden) at /usr/src/debug/qemu-2.11.50/hw/block/virtio-blk.c:426 #7 0x000002aa338c7b78 in virtio_blk_handle_vq (s=0x2aa4f2507c8, vq=0x3ff869df010) at /usr/src/debug/qemu-2.11.50/hw/block/virtio-blk.c:620 #8 0x000002aa338ebdf2 in virtio_queue_notify_aio_vq (vq=0x3ff869df010) at /usr/src/debug/qemu-2.11.50/hw/virtio/virtio.c:1515 #9 0x000002aa33b2df46 in aio_dispatch_handlers (address@hidden) at util/aio-posix.c:406 #10 0x000002aa33b2eb50 in aio_poll (ctx=0x2aa4f0ca050, address@hidden) at util/aio-posix.c:692 #11 0x000002aa33957f6a in iothread_run (opaque=0x2aa4f0c9630) at iothread.c:60
#12 0x000003ff86987e82 in start_thread () from /lib64/libpthread.so.0
#13 0x000003ff85a11596 in thread_start () from /lib64/libc.so.6
Backtrace stopped: previous frame identical to this frame (corrupt stack?)




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