On Tue, Jan 14, 2020 at 04:16:24PM +0000, Stefan Hajnoczi wrote: > On Tue, Jan 14, 2020 at 10:50:58AM +0800, Eryu Guan wrote: > > On Mon, Jan 13, 2020 at 04:38:55PM +0000, Stefan Hajnoczi wrote: > > > On Thu, Jan 09, 2020 at 12:58:06PM +0800, Eryu Guan wrote: > > > > On Tue, Jan 07, 2020 at 03:01:01PM +0100, Julia Suvorova wrote: > > > > > On Tue, Jan 7, 2020 at 2:06 PM Eryu Guan <eg...@linux.alibaba.com> > > > > > wrote: > > > > > > > > > > > > On Thu, Jan 02, 2020 at 10:08:50AM +0800, Eryu Guan wrote: > > > > > > > On Tue, Dec 31, 2019 at 11:51:35AM +0100, Igor Mammedov wrote: > > > > > > > > On Tue, 31 Dec 2019 18:34:34 +0800 > > > > > > > > Eryu Guan <eg...@linux.alibaba.com> wrote: > > > > > > > > > > > > > > > > > Hi, > > > > > > > > > > > > > > > > > > I'm using qemu 4.0 and hit segfault when tearing down kata > > > > > > > > > sandbox, I > > > > > > > > > think it's because io completion hits use-after-free when > > > > > > > > > device is > > > > > > > > > already gone. Is this a known bug that has been fixed? (I > > > > > > > > > went through > > > > > > > > > the git log but didn't find anything obvious). > > > > > > > > > > > > > > > > > > gdb backtrace is: > > > > > > > > > > > > > > > > > > Core was generated by `/usr/local/libexec/qemu-kvm -name > > > > > > > > > sandbox-5b8df8c6c6901c3c0a9b02879be10fe8d69d6'. > > > > > > > > > Program terminated with signal 11, Segmentation fault. > > > > > > > > > #0 object_get_class (obj=obj@entry=0x0) at > > > > > > > > > /usr/src/debug/qemu-4.0/qom/object.c:903 > > > > > > > > > 903 return obj->class; > > > > > > > > > (gdb) bt > > > > > > > > > #0 object_get_class (obj=obj@entry=0x0) at > > > > > > > > > /usr/src/debug/qemu-4.0/qom/object.c:903 > > > > > > > > > #1 0x0000558a2c009e9b in virtio_notify_vector > > > > > > > > > (vdev=0x558a2e7751d0, > > > > > > > > > vector=<optimized out>) at > > > > > > > > > /usr/src/debug/qemu-4.0/hw/virtio/virtio.c:1118 > > > > > > > > > #2 0x0000558a2bfdcb1e in > > > > > > > > > virtio_blk_discard_write_zeroes_complete ( > > > > > > > > > opaque=0x558a2f2fd420, ret=0) > > > > > > > > > at /usr/src/debug/qemu-4.0/hw/block/virtio-blk.c:186 > > > > > > > > > #3 0x0000558a2c261c7e in blk_aio_complete > > > > > > > > > (acb=0x558a2eed7420) > > > > > > > > > at /usr/src/debug/qemu-4.0/block/block-backend.c:1305 > > > > > > > > > #4 0x0000558a2c3031db in coroutine_trampoline (i0=<optimized > > > > > > > > > out>, > > > > > > > > > i1=<optimized out>) at > > > > > > > > > /usr/src/debug/qemu-4.0/util/coroutine-ucontext.c:116 > > > > > > > > > #5 0x00007f45b2f8b080 in ?? () from /lib64/libc.so.6 > > > > > > > > > #6 0x00007fff9ed75780 in ?? () > > > > > > > > > #7 0x0000000000000000 in ?? () > > > > > > > > > > > > > > > > > > It seems like qemu was completing a discard/write_zero > > > > > > > > > request, but > > > > > > > > > parent BusState was already freed & set to NULL. > > > > > > > > > > > > > > > > > > Do we need to drain all pending request before unrealizing > > > > > > > > > virtio-blk > > > > > > > > > device? Like the following patch proposed? > > > > > > > > > > > > > > > > > > https://lists.gnu.org/archive/html/qemu-devel/2017-06/msg02945.html > > > > > > > > > > > > > > > > > > If more info is needed, please let me know. > > > > > > > > > > > > > > > > may be this will help: > > > > > > > > https://patchwork.kernel.org/patch/11213047/ > > > > > > > > > > > > > > Yeah, this looks promising! I'll try it out (though it's a > > > > > > > one-time > > > > > > > crash for me). Thanks! > > > > > > > > > > > > After applying this patch, I don't see the original segfaut and > > > > > > backtrace, but I see this crash > > > > > > > > > > > > [Thread debugging using libthread_db enabled] > > > > > > Using host libthread_db library "/lib64/libthread_db.so.1". > > > > > > Core was generated by `/usr/local/libexec/qemu-kvm -name > > > > > > sandbox-a2f34a11a7e1449496503bbc4050ae040c0d3'. > > > > > > Program terminated with signal 11, Segmentation fault. > > > > > > #0 0x0000561216a57609 in virtio_pci_notify_write > > > > > > (opaque=0x5612184747e0, addr=0, val=<optimized out>, > > > > > > size=<optimized out>) at > > > > > > /usr/src/debug/qemu-4.0/hw/virtio/virtio-pci.c:1324 > > > > > > 1324 VirtIOPCIProxy *proxy = > > > > > > VIRTIO_PCI(DEVICE(vdev)->parent_bus->parent); > > > > > > Missing separate debuginfos, use: debuginfo-install > > > > > > glib2-2.42.2-5.1.alios7.x86_64 glibc-2.17-260.alios7.x86_64 > > > > > > libgcc-4.8.5-28.alios7.1.x86_64 libseccomp-2.3.1-3.alios7.x86_64 > > > > > > libstdc++-4.8.5-28.alios7.1.x86_64 > > > > > > numactl-libs-2.0.9-5.1.alios7.x86_64 > > > > > > pixman-0.32.6-3.1.alios7.x86_64 zlib-1.2.7-16.2.alios7.x86_64 > > > > > > (gdb) bt > > > > > > #0 0x0000561216a57609 in virtio_pci_notify_write > > > > > > (opaque=0x5612184747e0, addr=0, val=<optimized out>, > > > > > > size=<optimized out>) at > > > > > > /usr/src/debug/qemu-4.0/hw/virtio/virtio-pci.c:1324 > > > > > > #1 0x0000561216835b22 in memory_region_write_accessor > > > > > > (mr=<optimized out>, addr=<optimized out>, value=<optimized out>, > > > > > > size=<optimized out>, shift=<optimized out>, mask=<optimized out>, > > > > > > attrs=...) at /usr/src/debug/qemu-4.0/memory.c:502 > > > > > > #2 0x0000561216833c5d in access_with_adjusted_size > > > > > > (addr=addr@entry=0, value=value@entry=0x7fcdeab1b8a8, > > > > > > size=size@entry=2, access_size_min=<optimized out>, > > > > > > access_size_max=<optimized out>, access_fn=0x561216835ac0 > > > > > > <memory_region_write_accessor>, mr=0x56121846d340, attrs=...) > > > > > > at /usr/src/debug/qemu-4.0/memory.c:568 > > > > > > #3 0x0000561216837c66 in memory_region_dispatch_write > > > > > > (mr=mr@entry=0x56121846d340, addr=0, data=<optimized out>, size=2, > > > > > > attrs=attrs@entry=...) at /usr/src/debug/qemu-4.0/memory.c:1503 > > > > > > #4 0x00005612167e036f in flatview_write_continue > > > > > > (fv=fv@entry=0x56121852edd0, addr=addr@entry=841813602304, > > > > > > attrs=..., buf=buf@entry=0x7fce7dd97028 <Address 0x7fce7dd97028 out > > > > > > of bounds>, len=len@entry=2, addr1=<optimized out>, l=<optimized > > > > > > out>, mr=0x56121846d340) > > > > > > at /usr/src/debug/qemu-4.0/exec.c:3279 > > > > > > #5 0x00005612167e0506 in flatview_write (fv=0x56121852edd0, > > > > > > addr=841813602304, attrs=..., buf=0x7fce7dd97028 <Address > > > > > > 0x7fce7dd97028 out of bounds>, len=2) at > > > > > > /usr/src/debug/qemu-4.0/exec.c:3318 > > > > > > #6 0x00005612167e4a1b in address_space_write (as=<optimized out>, > > > > > > addr=<optimized out>, attrs=..., buf=<optimized out>, > > > > > > len=<optimized out>) at /usr/src/debug/qemu-4.0/exec.c:3408 > > > > > > #7 0x00005612167e4aa5 in address_space_rw (as=<optimized out>, > > > > > > addr=<optimized out>, attrs=..., attrs@entry=..., > > > > > > buf=buf@entry=0x7fce7dd97028 <Address 0x7fce7dd97028 out of > > > > > > bounds>, len=<optimized out>, is_write=<optimized out>) at > > > > > > /usr/src/debug/qemu-4.0/exec.c:3419 > > > > > > #8 0x0000561216849da1 in kvm_cpu_exec > > > > > > (cpu=cpu@entry=0x56121849aa00) at > > > > > > /usr/src/debug/qemu-4.0/accel/kvm/kvm-all.c:2034 > > > > > > #9 0x000056121682255e in qemu_kvm_cpu_thread_fn > > > > > > (arg=arg@entry=0x56121849aa00) at > > > > > > /usr/src/debug/qemu-4.0/cpus.c:1281 > > > > > > #10 0x0000561216b794d6 in qemu_thread_start (args=<optimized out>) > > > > > > at /usr/src/debug/qemu-4.0/util/qemu-thread-posix.c:502 > > > > > > #11 0x00007fce7bef6e25 in start_thread () from > > > > > > /lib64/libpthread.so.0 > > > > > > #12 0x00007fce7bc1ef1d in clone () from /lib64/libc.so.6 > > > > > > > > > > > > And I searched and found > > > > > > https://bugzilla.redhat.com/show_bug.cgi?id=1706759 , which has the > > > > > > same > > > > > > backtrace as above, and it seems commit 7bfde688fb1b ("virtio-blk: > > > > > > Add > > > > > > blk_drain() to virtio_blk_device_unrealize()") is to fix this > > > > > > particular > > > > > > bug. > > > > > > > > > > > > But I can still hit the bug even after applying the commit. Do I > > > > > > miss > > > > > > anything? > > > > > > > > > > Hi Eryu, > > > > > This backtrace seems to be caused by this bug (there were two bugs in > > > > > 1706759): https://bugzilla.redhat.com/show_bug.cgi?id=1708480 > > > > > Although the solution hasn't been tested on virtio-blk yet, you may > > > > > want to apply this patch: > > > > > > > > > > https://lists.nongnu.org/archive/html/qemu-devel/2019-12/msg05197.html > > > > > Let me know if this works. > > > > > > > > Unfortunately, I still see the same segfault & backtrace after applying > > > > commit 421afd2fe8dd ("virtio: reset region cache when on queue > > > > deletion") > > > > > > > > Anything I can help to debug? > > > > > > Please post the QEMU command-line and the QMP commands use to remove the > > > device. > > > > It's a normal kata instance using virtio-fs as rootfs. > > > > /usr/local/libexec/qemu-kvm -name > > sandbox-a670786fcb1758d2348eb120939d90ffacf9f049f10b337284ad49bbcd60936d \ > > -uuid e03f6b6b-b80b-40c0-8d5b-0cbfed1305d2 -machine > > q35,accel=kvm,kernel_irqchip,nvdimm,nosmm,nosmbus,nosata,nopit \ > > -cpu host -qmp > > unix:/run/vc/vm/a670786fcb1758d2348eb120939d90ffacf9f049f10b337284ad49bbcd60936d/qmp.sock,server,nowait > > \ > > -qmp > > unix:/run/vc/vm/debug-a670786fcb1758d2348eb120939d90ffacf9f049f10b337284ad49bbcd60936d/qmp.sock,server,nowait > > \ > > -m 2048M,slots=10,maxmem=773893M -device > > pci-bridge,bus=pcie.0,id=pci-bridge-0,chassis_nr=1,shpc=on,addr=2,romfile= \ > > -device virtio-serial-pci,disable-modern=false,id=serial0,romfile= -device > > virtconsole,chardev=charconsole0,id=console0 \ > > -chardev > > socket,id=charconsole0,path=/run/vc/vm/a670786fcb1758d2348eb120939d90ffacf9f049f10b337284ad49bbcd60936d/console.sock,server,nowait > > \ > > -device > > virtserialport,chardev=metricagent,id=channel10,name=metric.agent.channel.10 > > \ > > -chardev > > socket,id=metricagent,path=/run/vc/vm/a670786fcb1758d2348eb120939d90ffacf9f049f10b337284ad49bbcd60936d/metric.agent.channel.sock,server,nowait > > \ > > -device nvdimm,id=nv0,memdev=mem0 -object > > memory-backend-file,id=mem0,mem-path=/usr/local/share/containers-image-1.9.0.img,size=268435456 > > \ > > -object rng-random,id=rng0,filename=/dev/urandom -device > > virtio-rng,rng=rng0,romfile= \ > > -device virtserialport,chardev=charch0,id=channel0,name=agent.channel.0 \ > > -chardev > > socket,id=charch0,path=/run/vc/vm/a670786fcb1758d2348eb120939d90ffacf9f049f10b337284ad49bbcd60936d/kata.sock,server,nowait > > \ > > -chardev > > socket,id=char-6fca044b801a78a1,path=/run/vc/vm/a670786fcb1758d2348eb120939d90ffacf9f049f10b337284ad49bbcd60936d/vhost-fs.sock > > \ > > -device > > vhost-user-fs-pci,chardev=char-6fca044b801a78a1,tag=kataShared,cache-size=8192M > > -netdev tap,id=network-0,vhost=on,vhostfds=3,fds=4 \ > > -device > > driver=virtio-net-pci,netdev=network-0,mac=76:57:f1:ab:51:5c,disable-modern=false,mq=on,vectors=4,romfile= > > \ > > -global kvm-pit.lost_tick_policy=discard -vga none -no-user-config > > -nodefaults -nographic -daemonize \ > > -object memory-backend-file,id=dimm1,size=2048M,mem-path=/dev/shm,share=on > > -numa node,memdev=dimm1 -kernel /usr/local/share/kernel \ > > -append tsc=reliable no_timer_check rcupdate.rcu_expedited=1 > > i8042.direct=1 i8042.dumbkbd=1 i8042.nopnp=1 i8042.noaux=1 noreplace-smp > > reboot=k console=hvc0 console=hvc1 iommu=off cryptomgr.notests > > net.ifnames=0 pci=lastbus=0 root=/dev/pmem0p1 > > rootflags=dax,data=ordered,errors=remount-ro ro rootfstype=ext4 quiet > > systemd.show_status=false panic=1 nr_cpus=96 agent.use_vsock=false > > init=/usr/lib/systemd/systemd systemd.unit=kata-containers.target > > systemd.mask=systemd-networkd.service systemd.mask=systemd-networkd.socket \ > > -pidfile > > /run/vc/vm/a670786fcb1758d2348eb120939d90ffacf9f049f10b337284ad49bbcd60936d/pid > > \ > > -smp 1,cores=1,threads=1,sockets=96,maxcpus=96 > > > > QMP command to delete device (the device id is just an example, not the > > one caused the crash): > > > > "{\"arguments\":{\"id\":\"virtio-drive-5967abfb917c8da6\"},\"execute\":\"device_del\"}" > > > > which has been hot plugged by: > > "{\"arguments\":{\"cache\":{\"direct\":true,\"no-flush\":false},\"driver\":\"raw\",\"file\":{\"driver\":\"file\",\"filename\":\"/dev/dm-18\"},\"node-name\":\"drive-5967abfb917c8da6\"},\"execute\":\"blockdev-add\"}" > > "{\"return\": {}}" > > "{\"arguments\":{\"addr\":\"01\",\"bus\":\"pci-bridge-0\",\"drive\":\"drive-5967abfb917c8da6\",\"driver\":\"virtio-blk-pci\",\"id\":\"virtio-drive-5967abfb917c8da6\",\"romfile\":\"\",\"share-rw\":\"on\"},\"execute\":\"device_add\"}" > > "{\"return\": {}}" > > Thanks. I wasn't able to reproduce this crash with qemu.git/master. > > One thing that is strange about the latest backtrace you posted: QEMU is > dispatching the memory access instead of using the ioeventfd code that > that virtio-blk-pci normally takes when a virtqueue is notified. I > guess this means ioeventfd has already been disabled due to the hot > unplug. > > Could you try with machine type "i440fx" instead of "q35"? I wonder if > pci-bridge/shpc is part of the problem.
Sure, will try it. But it may take some time, as the test bed is busy with other testing tasks. I'll report back once I got the results. Thanks, Eryu
