On Tue, Oct 02, 2018 at 01:54:25PM +0400, Marc-André Lureau wrote:
> Hi
>
> On Thu, Sep 27, 2018 at 7:37 PM Liang Li <liliang...@didiglobal.com> wrote:
> >
> > During live migration, when stopping vhost-user device, 'vhost_dev_stop'
> > will be called, 'vhost_dev_stop' will call a batch of 'vhost_user_read'
> > and 'vhost_user_write'. If a previous 'vhost_user_read' or
> > 'vhost_user_write'
> > failed because the vhost user backend failed, the 'CHR_EVENT_CLOSED' event
> > will be triggerd, followed by the call chain
> > chr_closed_bh()->vhost_user_stop()->
> > vhost_net_cleanup()->vhost_dev_cleanup()
> >
> > vhost_dev_cleanup will clear vhost_dev struct, so the later
> > 'vhost_user_read'
> > or 'vhost_user_read' will reference null pointer and cause qemu crash
>
> Do you have a backtrace to help understand the issue?
> thanks
>
sorry for late response.
Yes, I have. But it's the backtrace for qemu-kvm-2.10.
and we found this issue when doing pressure test, it was triggered
by a buggy ovs-dpdk backend, an ovs-dpdk coredump followed by a qemu
coredump.
the backtrace is like bellow:
======================================================================
0 0x00007f0af85ea069 in vhost_user_read (msg=msg@entry=0x7f0a2a4b5300,
dev=0x7f0afaee0340) at /usr/src/debug/qemu-2.10.0/hw/virtio/vhost-user.c:139
1 0x00007f0af85ea2df in vhost_user_get_vring_base (dev=0x7f0afaee0340,
ring=0x7f0a2a4b5450) at /usr/src/debug/qemu-2.10.0/hw/virtio/vhost-user.c:458
2 0x00007f0af85e715e in vhost_virtqueue_stop
(dev=dev@entry=0x7f0afaee0340, vdev=vdev@entry=0x7f0afcba0170,
vq=0x7f0afaee05d0, idx=1)
at /usr/src/debug/qemu-2.10.0/hw/virtio/vhost.c:1138
3 0x00007f0af85e8e24 in vhost_dev_stop (hdev=hdev@entry=0x7f0afaee0340,
vdev=vdev@entry=0x7f0afcba0170) at
/usr/src/debug/qemu-2.10.0/hw/virtio/vhost.c:1601
4 0x00007f0af85d1418 in vhost_net_stop_one (net=0x7f0afaee0340,
dev=0x7f0afcba0170) at /usr/src/debug/qemu-2.10.0/hw/net/vhost_net.c:289
5 0x00007f0af85d191b in vhost_net_stop (dev=dev@entry=0x7f0afcba0170,
ncs=<optimized out>, total_queues=total_queues@entry=1) at
/usr/src/debug/qemu-2.10.0/hw/net/vhost_net.c:3
6 0x00007f0af85ceba6 in virtio_net_set_status (status=<optimized out>,
n=0x7f0afcba0170) at /usr/src/debug/qemu-2.10.0/hw/net/virtio-net.c:180
7 0x00007f0af85ceba6 in virtio_net_set_status (vdev=0x7f0afcba0170,
status=15 '\017') at /usr/src/debug/qemu-2.10.0/hw/net/virtio-net.c:254
8 0x00007f0af85e0f2c in virtio_set_status (vdev=0x7f0afcba0170,
val=<optimized out>) at /usr/src/debug/qemu-2.10.0/hw/virtio/virtio.c:1147
9 0x00007f0af866dce2 in vm_state_notify (running=running@entry=0,
state=state@entry=RUN_STATE_FINISH_MIGRATE) at vl.c:1623
10 0x00007f0af858f11a in do_vm_stop (state=RUN_STATE_FINISH_MIGRATE,
send_stop=send_stop@entry=true) at /usr/src/debug/qemu-2.10.0/cpus.c:941
11 0x00007f0af858f159 in vm_stop (state=<optimized out>) at
/usr/src/debug/qemu-2.10.0/cpus.c:1818
12 0x00007f0af858f296 in vm_stop_force_state
(state=state@entry=RUN_STATE_FINISH_MIGRATE) at
/usr/src/debug/qemu-2.10.0/cpus.c:1868
13 0x00007f0af87551d7 in migration_thread (start_time=<synthetic pointer>,
old_vm_running=<synthetic pointer>, current_active_state=4, s=0x7f0afaf00500)
at migration/migration.c:1956
14 0x00007f0af87551d7 in migration_thread (opaque=0x7f0afaf00500) at
migration/migration.c:2129
15 0x00007f0af217fdc5 in start_thread () at /lib64/libpthread.so.0
16 0x00007f0af1eae73d in clone () at /lib64/libc.so.6
(gdb) l
134 }
135
136 static int vhost_user_read(struct vhost_dev *dev, VhostUserMsg *msg)
137 {
138 struct vhost_user *u = dev->opaque;
139 CharBackend *chr = u->chr;
140 uint8_t *p = (uint8_t *) msg;
141 int r, size = VHOST_USER_HDR_SIZE;
142
143 r = qemu_chr_fe_read_all(chr, p, size);
144 if (r != size) {
145 error_report("Failed to read msg header. Read %d instead of %d."
146 " Original request %d.", r, size, msg->request);
147 goto fail;
148 }
149
150 /* validate received flags */
151 if (msg->flags != (VHOST_USER_REPLY_MASK | VHOST_USER_VERSION)) {
152 error_report("Failed to read msg header."
153 " Flags 0x%x instead of 0x%x.", msg->flags,
(gdb) p u
$1 = (struct vhost_user *) 0x0
(gdb) p dev
$2 = (struct vhost_dev *) 0x7f0afaee0340
(gdb) p *dev
$3 = {vdev = 0x0, memory_listener = {begin = 0x0, commit = 0x0, region_add
= 0x0, region_del = 0x0, region_nop = 0x0, log_start = 0x0, log_stop = 0x0,
log_sync = 0x0,
log_global_start = 0x0, log_global_stop = 0x0, eventfd_add = 0x0,
eventfd_del = 0x0, coalesced_mmio_add = 0x0, coalesced_mmio_del = 0x0, priority
= 0, address_space = 0x0,
link = {tqe_next = 0x0, tqe_prev = 0x0}, link_as = {tqe_next = 0x0,
tqe_prev = 0x0}}, iommu_listener = {begin = 0x0, commit = 0x0, region_add =
0x0, region_del = 0x0,
region_nop = 0x0, log_start = 0x0, log_stop = 0x0, log_sync = 0x0,
log_global_start = 0x0, log_global_stop = 0x0, eventfd_add = 0x0, eventfd_del =
0x0, coalesced_mmio_add =
0x0, coalesced_mmio_del = 0x0, priority = 0, address_space = 0x0, link
= {tqe_next = 0x0, tqe_prev = 0x0}, link_as = {tqe_next = 0x0, tqe_prev =
0x0}}, mem = 0x0,
n_mem_sections = 0, mem_sections = 0x0, vqs = 0x0, nvqs = 0, vq_index =
0, features = 0, acked_features = 0, backend_features = 0, protocol_features =
0, max_queues = 0,
started = false, log_enabled = false, log_size = 0, migration_blocker =
0x0, memory_changed = false, mem_changed_start_addr = 0, mem_changed_end_addr =
0, vhost_ops = 0x0,
opaque = 0x0, log = 0x0, entry = {le_next = 0x0, le_prev = 0x0},
iommu_list = {lh_first = 0x0}, n = {notify = 0x0, notifier_flags =
IOMMU_NOTIFIER_NONE, start = 0, end = 0,
node = {le_next = 0x0, le_prev = 0x0}}}
========================================================================
I checked the latest upstream qemu code, and found there was no new fix for
this issue.
Liang
> >
> > Signed-off-by: Liang Li <liliang...@didiglobal.com>
> > ---
> > hw/net/vhost_net.c | 6 ++++++
> > hw/virtio/vhost-user.c | 15 +++++++++++++--
> > include/hw/virtio/vhost.h | 1 +
> > include/net/vhost_net.h | 1 +
> > net/vhost-user.c | 3 +++
> > 5 files changed, 24 insertions(+), 2 deletions(-)
> >
> > diff --git a/hw/net/vhost_net.c b/hw/net/vhost_net.c
> > index e037db6..77994e9 100644
> > --- a/hw/net/vhost_net.c
> > +++ b/hw/net/vhost_net.c
> > @@ -113,6 +113,11 @@ uint64_t vhost_net_get_features(struct vhost_net *net,
> > uint64_t features)
> > features);
> > }
> >
> > +void vhost_net_mark_break_down(struct vhost_net *net)
> > +{
> > + net->dev.break_down = true;
> > +}
> > +
> > void vhost_net_ack_features(struct vhost_net *net, uint64_t features)
> > {
> > net->dev.acked_features = net->dev.backend_features;
> > @@ -156,6 +161,7 @@ struct vhost_net *vhost_net_init(VhostNetOptions
> > *options)
> > net->dev.max_queues = 1;
> > net->dev.nvqs = 2;
> > net->dev.vqs = net->vqs;
> > + net->dev.break_down = false;
> >
> > if (backend_kernel) {
> > r = vhost_net_get_fd(options->net_backend);
> > diff --git a/hw/virtio/vhost-user.c b/hw/virtio/vhost-user.c
> > index b041343..1394719 100644
> > --- a/hw/virtio/vhost-user.c
> > +++ b/hw/virtio/vhost-user.c
> > @@ -213,14 +213,20 @@ static bool ioeventfd_enabled(void)
> > static int vhost_user_read(struct vhost_dev *dev, VhostUserMsg *msg)
> > {
> > struct vhost_user *u = dev->opaque;
> > - CharBackend *chr = u->user->chr;
> > + CharBackend *chr;
> > uint8_t *p = (uint8_t *) msg;
> > int r, size = VHOST_USER_HDR_SIZE;
> >
> > + if (dev->break_down) {
> > + goto fail;
> > + }
> > +
> > + chr = u->user->chr;
> > r = qemu_chr_fe_read_all(chr, p, size);
> > if (r != size) {
> > error_report("Failed to read msg header. Read %d instead of %d."
> > " Original request %d.", r, size, msg->hdr.request);
> > + dev->break_down = true;
> > goto fail;
> > }
> >
> > @@ -299,9 +305,12 @@ static int vhost_user_write(struct vhost_dev *dev,
> > VhostUserMsg *msg,
> > int *fds, int fd_num)
> > {
> > struct vhost_user *u = dev->opaque;
> > - CharBackend *chr = u->user->chr;
> > + CharBackend *chr;
> > int ret, size = VHOST_USER_HDR_SIZE + msg->hdr.size;
> >
> > + if (dev->break_down) {
> > + return -1;
> > + }
> > /*
> > * For non-vring specific requests, like VHOST_USER_SET_MEM_TABLE,
> > * we just need send it once in the first time. For later such
> > @@ -312,6 +321,7 @@ static int vhost_user_write(struct vhost_dev *dev,
> > VhostUserMsg *msg,
> > return 0;
> > }
> >
> > + chr = u->user->chr;
> > if (qemu_chr_fe_set_msgfds(chr, fds, fd_num) < 0) {
> > error_report("Failed to set msg fds.");
> > return -1;
> > @@ -319,6 +329,7 @@ static int vhost_user_write(struct vhost_dev *dev,
> > VhostUserMsg *msg,
> >
> > ret = qemu_chr_fe_write_all(chr, (const uint8_t *) msg, size);
> > if (ret != size) {
> > + dev->break_down = true;
> > error_report("Failed to write msg."
> > " Wrote %d instead of %d.", ret, size);
> > return -1;
> > diff --git a/include/hw/virtio/vhost.h b/include/hw/virtio/vhost.h
> > index a7f449f..86d0dc5 100644
> > --- a/include/hw/virtio/vhost.h
> > +++ b/include/hw/virtio/vhost.h
> > @@ -74,6 +74,7 @@ struct vhost_dev {
> > bool started;
> > bool log_enabled;
> > uint64_t log_size;
> > + bool break_down;
> > Error *migration_blocker;
> > const VhostOps *vhost_ops;
> > void *opaque;
> > diff --git a/include/net/vhost_net.h b/include/net/vhost_net.h
> > index 77e4739..06f2c08 100644
> > --- a/include/net/vhost_net.h
> > +++ b/include/net/vhost_net.h
> > @@ -27,6 +27,7 @@ void vhost_net_cleanup(VHostNetState *net);
> >
> > uint64_t vhost_net_get_features(VHostNetState *net, uint64_t features);
> > void vhost_net_ack_features(VHostNetState *net, uint64_t features);
> > +void vhost_net_mark_break_down(VHostNetState *net);
> >
> > bool vhost_net_virtqueue_pending(VHostNetState *net, int n);
> > void vhost_net_virtqueue_mask(VHostNetState *net, VirtIODevice *dev,
> > diff --git a/net/vhost-user.c b/net/vhost-user.c
> > index a39f9c9..b99e20b 100644
> > --- a/net/vhost-user.c
> > +++ b/net/vhost-user.c
> > @@ -270,6 +270,9 @@ static void net_vhost_user_event(void *opaque, int
> > event)
> > if (s->watch) {
> > AioContext *ctx = qemu_get_current_aio_context();
> >
> > + if (s->vhost_net) {
> > + vhost_net_mark_break_down(s->vhost_net);
> > + }
> > g_source_remove(s->watch);
> > s->watch = 0;
> > qemu_chr_fe_set_handlers(&s->chr, NULL, NULL, NULL, NULL,
> > --
> > 1.8.3.1
> >
> >
>
>
> --
> Marc-André Lureau
>
