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
>
> 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
