When a guest virtual machine was configured as a vhost-user server and the back end was restarted, the guest was not able to recover. With this update, the back end is able to discard the SET_VRING_BASE value and resume from index. This allows the guest to recover successfully in the described scenario.
Description of problem:
Boot guest with vhostuser server mode, QEMU prompt 'Segmentation fault' after executing '(qemu)system_powerdown'.
Version-Release number of selected component (if applicable):
host:
3.10.0-460.el7.x86_64
qemu-kvm-rhev-2.6.0-12.el7.x86_64
guest:
3.10.0-456.el7.x86_64
How reproducible:
100%
Steps to Reproduce:
1. Run a slirp/vlan in a background process
# /usr/libexec/qemu-kvm \
-net none \
-net socket,vlan=0,udp=localhost:4444,localaddr=localhost:5555 \
-net user,vlan=0
2. Start qemu with vhost-user as server mode
# /usr/libexec/qemu-kvm -m 1024 -smp 2 \
-object memory-backend-file,id=mem,size=1024M,mem-path=/dev/hugepages,share=on \
-numa node,memdev=mem -mem-prealloc \
-chardev socket,id=char0,path=/tmp/vubr.sock,server \
-netdev type=vhost-user,id=mynet1,chardev=char0,vhostforce \
-device virtio-net-pci,netdev=mynet1,mac=54:52:00:1a:2c:01 \
/home/pezhang/rhel7.3.qcow2 \
-monitor stdio \
-vga std -vnc :10 \
QEMU waiting for connection on: disconnected:unix:/tmp/vubr.sock,server
3. Start vubr as vhostuser client
# ./vhost-user-bridge -c
4. After guest boot up, shutdown it. Qemu will prompt error info.
(qemu) system_powerdown
(qemu) Segmentation fault
Actual results:
Qemu doesn't quit well.
Expected results:
Qemu should quit correctly without any error info.
Additional info:
1. gdb info
(qemu) system_powerdown
(qemu)
Program received signal SIGSEGV, Segmentation fault.
0x00005555558f3128 in object_class_dynamic_cast (class=class@entry=0x55555945ee80,
typename=typename@entry=0x5555559c33f9 "qio-channel") at qom/object.c:662
662 if (type->class->interfaces &&
...
(gdb) bt
#0 0x00005555558f3128 in object_class_dynamic_cast (class=class@entry=0x55555945ee80,
typename=typename@entry=0x5555559c33f9 "qio-channel") at qom/object.c:662
#1 0x00005555558f32b5 in object_class_dynamic_cast_assert (class=0x55555945ee80,
typename=typename@entry=0x5555559c33f9 "qio-channel", file=file@entry=0x555555a3f366 "io/channel.c", line=line@entry=60,
func=func@entry=0x555555a3f500 <__func__.20656> "qio_channel_writev_full") at qom/object.c:712
#2 0x000055555595b817 in qio_channel_writev_full (ioc=0x55555945ef80, iov=0x7fffffff9890, niov=1, fds=0x0, nfds=0, errp=0x0)
at io/channel.c:60
#3 0x00005555557c6974 in io_channel_send_full (ioc=0x55555945ef80, buf=0x7fffffff99a0, len=20, fds=0x0, nfds=0)
at qemu-char.c:966
#4 0x00005555557c6a33 in tcp_chr_write (chr=<optimized out>, buf=<optimized out>, len=<optimized out>) at qemu-char.c:2658
#5 0x00005555557c76eb in qemu_chr_fe_write_buffer (s=s@entry=0x555556c03c20, buf=buf@entry=0x7fffffff99a0 "\v", len=20,
offset=offset@entry=0x7fffffff9950) at qemu-char.c:250
#6 0x00005555557ca073 in qemu_chr_fe_write_all (s=s@entry=0x555556c03c20, buf=buf@entry=0x7fffffff99a0 "\v",
len=len@entry=20) at qemu-char.c:310
#7 0x0000555555749f1f in vhost_user_write (msg=msg@entry=0x7fffffff99a0, fds=fds@entry=0x0, fd_num=fd_num@entry=0,
dev=0x555556b3dc00, dev=0x555556b3dc00) at /usr/src/debug/qemu-2.6.0/hw/virtio/vhost-user.c:195
#8 0x000055555574aa2c in vhost_user_get_vring_base (dev=0x555556b3dc00, ring=0x7fffffff9ae0)
at /usr/src/debug/qemu-2.6.0/hw/virtio/vhost-user.c:364
#9 0x00005555557481b0 in vhost_virtqueue_stop (dev=dev@entry=0x555556b3dc00, vdev=vdev@entry=0x555559c14328,
vq=0x555556b3dd38, idx=0) at /usr/src/debug/qemu-2.6.0/hw/virtio/vhost.c:924
#10 0x00005555557497c4 in vhost_dev_stop (hdev=hdev@entry=0x555556b3dc00, vdev=vdev@entry=0x555559c14328)
at /usr/src/debug/qemu-2.6.0/hw/virtio/vhost.c:1290
#11 0x0000555555735c28 in vhost_net_stop_one (net=0x555556b3dc00, dev=dev@entry=0x555559c14328)
at /usr/src/debug/qemu-2.6.0/hw/net/vhost_net.c:288
#12 0x000055555573610b in vhost_net_stop (dev=dev@entry=0x555559c14328, ncs=<optimized out>,
total_queues=total_queues@entry=1) at /usr/src/debug/qemu-2.6.0/hw/net/vhost_net.c:367
#13 0x0000555555733455 in virtio_net_vhost_status (status=7 '\a', n=0x555559c14328)
at /usr/src/debug/qemu-2.6.0/hw/net/virtio-net.c:158
#14 virtio_net_set_status (vdev=<optimized out>, status=<optimized out>) at /usr/src/debug/qemu-2.6.0/hw/net/virtio-net.c:224
---Type <return> to continue, or q <return> to quit---
#15 0x00005555558b720f in qmp_set_link (name=name@entry=0x555556b30bd0 "mynet1", up=up@entry=false,
errp=errp@entry=0x7fffffffbc68) at net/net.c:1368
#16 0x00005555558bd7ef in net_vhost_user_event (opaque=0x555556b30bd0, event=5) at net/vhost-user.c:226
#17 0x00005555557cc132 in qemu_chr_free (chr=0x555556c03c20) at qemu-char.c:4037
#18 0x00005555557cce7f in qemu_chr_cleanup () at qemu-char.c:4574
#19 0x00005555556c7611 in main (argc=<optimized out>, argv=<optimized out>, envp=<optimized out>) at vl.c:4676
2. This bug was caused by patches of Bug 1347077.
Verification:
Versions:qemu-kvm-rhev-2.6.0-15.el7.x86_64
Steps:
1. Run a slirp/vlan in a background process
2. Start qemu with vhost-user as server mode
3. Start vubr as vhostuser client
(Step1~3 have same commands and results as Description)
4. After guest boot up, shutdown it. Qemu quit well.
(qemu) system_powerdown
or
in guest:
# shutdown -h now
So this bug has been fixed well. Thank you.
Since the problem described in this bug report should be
resolved in a recent advisory, it has been closed with a
resolution of ERRATA.
For information on the advisory, and where to find the updated
files, follow the link below.
If the solution does not work for you, open a new bug report.
https://rhn.redhat.com/errata/RHBA-2016-2673.html
Description of problem: Boot guest with vhostuser server mode, QEMU prompt 'Segmentation fault' after executing '(qemu)system_powerdown'. Version-Release number of selected component (if applicable): host: 3.10.0-460.el7.x86_64 qemu-kvm-rhev-2.6.0-12.el7.x86_64 guest: 3.10.0-456.el7.x86_64 How reproducible: 100% Steps to Reproduce: 1. Run a slirp/vlan in a background process # /usr/libexec/qemu-kvm \ -net none \ -net socket,vlan=0,udp=localhost:4444,localaddr=localhost:5555 \ -net user,vlan=0 2. Start qemu with vhost-user as server mode # /usr/libexec/qemu-kvm -m 1024 -smp 2 \ -object memory-backend-file,id=mem,size=1024M,mem-path=/dev/hugepages,share=on \ -numa node,memdev=mem -mem-prealloc \ -chardev socket,id=char0,path=/tmp/vubr.sock,server \ -netdev type=vhost-user,id=mynet1,chardev=char0,vhostforce \ -device virtio-net-pci,netdev=mynet1,mac=54:52:00:1a:2c:01 \ /home/pezhang/rhel7.3.qcow2 \ -monitor stdio \ -vga std -vnc :10 \ QEMU waiting for connection on: disconnected:unix:/tmp/vubr.sock,server 3. Start vubr as vhostuser client # ./vhost-user-bridge -c 4. After guest boot up, shutdown it. Qemu will prompt error info. (qemu) system_powerdown (qemu) Segmentation fault Actual results: Qemu doesn't quit well. Expected results: Qemu should quit correctly without any error info. Additional info: 1. gdb info (qemu) system_powerdown (qemu) Program received signal SIGSEGV, Segmentation fault. 0x00005555558f3128 in object_class_dynamic_cast (class=class@entry=0x55555945ee80, typename=typename@entry=0x5555559c33f9 "qio-channel") at qom/object.c:662 662 if (type->class->interfaces && ... (gdb) bt #0 0x00005555558f3128 in object_class_dynamic_cast (class=class@entry=0x55555945ee80, typename=typename@entry=0x5555559c33f9 "qio-channel") at qom/object.c:662 #1 0x00005555558f32b5 in object_class_dynamic_cast_assert (class=0x55555945ee80, typename=typename@entry=0x5555559c33f9 "qio-channel", file=file@entry=0x555555a3f366 "io/channel.c", line=line@entry=60, func=func@entry=0x555555a3f500 <__func__.20656> "qio_channel_writev_full") at qom/object.c:712 #2 0x000055555595b817 in qio_channel_writev_full (ioc=0x55555945ef80, iov=0x7fffffff9890, niov=1, fds=0x0, nfds=0, errp=0x0) at io/channel.c:60 #3 0x00005555557c6974 in io_channel_send_full (ioc=0x55555945ef80, buf=0x7fffffff99a0, len=20, fds=0x0, nfds=0) at qemu-char.c:966 #4 0x00005555557c6a33 in tcp_chr_write (chr=<optimized out>, buf=<optimized out>, len=<optimized out>) at qemu-char.c:2658 #5 0x00005555557c76eb in qemu_chr_fe_write_buffer (s=s@entry=0x555556c03c20, buf=buf@entry=0x7fffffff99a0 "\v", len=20, offset=offset@entry=0x7fffffff9950) at qemu-char.c:250 #6 0x00005555557ca073 in qemu_chr_fe_write_all (s=s@entry=0x555556c03c20, buf=buf@entry=0x7fffffff99a0 "\v", len=len@entry=20) at qemu-char.c:310 #7 0x0000555555749f1f in vhost_user_write (msg=msg@entry=0x7fffffff99a0, fds=fds@entry=0x0, fd_num=fd_num@entry=0, dev=0x555556b3dc00, dev=0x555556b3dc00) at /usr/src/debug/qemu-2.6.0/hw/virtio/vhost-user.c:195 #8 0x000055555574aa2c in vhost_user_get_vring_base (dev=0x555556b3dc00, ring=0x7fffffff9ae0) at /usr/src/debug/qemu-2.6.0/hw/virtio/vhost-user.c:364 #9 0x00005555557481b0 in vhost_virtqueue_stop (dev=dev@entry=0x555556b3dc00, vdev=vdev@entry=0x555559c14328, vq=0x555556b3dd38, idx=0) at /usr/src/debug/qemu-2.6.0/hw/virtio/vhost.c:924 #10 0x00005555557497c4 in vhost_dev_stop (hdev=hdev@entry=0x555556b3dc00, vdev=vdev@entry=0x555559c14328) at /usr/src/debug/qemu-2.6.0/hw/virtio/vhost.c:1290 #11 0x0000555555735c28 in vhost_net_stop_one (net=0x555556b3dc00, dev=dev@entry=0x555559c14328) at /usr/src/debug/qemu-2.6.0/hw/net/vhost_net.c:288 #12 0x000055555573610b in vhost_net_stop (dev=dev@entry=0x555559c14328, ncs=<optimized out>, total_queues=total_queues@entry=1) at /usr/src/debug/qemu-2.6.0/hw/net/vhost_net.c:367 #13 0x0000555555733455 in virtio_net_vhost_status (status=7 '\a', n=0x555559c14328) at /usr/src/debug/qemu-2.6.0/hw/net/virtio-net.c:158 #14 virtio_net_set_status (vdev=<optimized out>, status=<optimized out>) at /usr/src/debug/qemu-2.6.0/hw/net/virtio-net.c:224 ---Type <return> to continue, or q <return> to quit--- #15 0x00005555558b720f in qmp_set_link (name=name@entry=0x555556b30bd0 "mynet1", up=up@entry=false, errp=errp@entry=0x7fffffffbc68) at net/net.c:1368 #16 0x00005555558bd7ef in net_vhost_user_event (opaque=0x555556b30bd0, event=5) at net/vhost-user.c:226 #17 0x00005555557cc132 in qemu_chr_free (chr=0x555556c03c20) at qemu-char.c:4037 #18 0x00005555557cce7f in qemu_chr_cleanup () at qemu-char.c:4574 #19 0x00005555556c7611 in main (argc=<optimized out>, argv=<optimized out>, envp=<optimized out>) at vl.c:4676 2. This bug was caused by patches of Bug 1347077.