fix: QEMU deadlock with dpdk-vdpa
QEMU start vhost-user with modern net and blk, backend use dpdk-vdpa process,
after live migration, dest QEMU deadlock with dpdk-vdpa
- QEMU sends VHOST_USER_SET_VRING_KICK to dpdk-vdpa net
- QEMU does not need to wait for a response to this message
- QEMU then sends VHOST_USER_SET_MEM_TABLE to dpdk-vdpa blk
- QEMU needs to wait reply in this message
- when dpdk-vdpa recv VHOST_USER_SET_VRING_KICK, it will send
VHOST_USER_BACKEND_VRING_HOST_NOTIFIER_MSG to QEMU
- dpdk-vdpa needs to wait for a response to this message
- since QEMU vhost_user_read and backend channel are synchronous in the same
thread
- QEMU will deadlock with dpdk-vdpa
Signed-off-by: Rma Ma <rma...@jaguarmicro.com>
---
hw/virtio/vhost-user.c | 67 ++++++++++++++++++++++++++++++++++++++----
1 file changed, 61 insertions(+), 6 deletions(-)
diff --git a/hw/virtio/vhost-user.c b/hw/virtio/vhost-user.c
index c4e0cbd702..1f6b3a5a63 100644
--- a/hw/virtio/vhost-user.c
+++ b/hw/virtio/vhost-user.c
@@ -274,6 +274,17 @@ struct scrub_regions {
int fd_idx;
};
+struct backend_thread {
+ QemuThread thread;
+ QemuSemaphore init_done_sem;
+ int thread_id;
+ GMainContext *ctxt;
+ GMainLoop *loop;
+};
+
+static struct backend_thread *backend_th;
+static bool backend_thread_run;
+
static bool ioeventfd_enabled(void)
{
return !kvm_enabled() || kvm_eventfds_enabled();
@@ -1696,7 +1707,8 @@ fdcleanup:
return rc;
}
-static int vhost_setup_backend_channel(struct vhost_dev *dev)
+static int vhost_setup_backend_channel(struct vhost_dev *dev,
+ GMainContext *ctxt)
{
VhostUserMsg msg = {
.hdr.request = VHOST_USER_SET_BACKEND_REQ_FD,
@@ -1728,7 +1740,7 @@ static int vhost_setup_backend_channel(struct vhost_dev
*dev)
u->backend_ioc = ioc;
u->backend_src = qio_channel_add_watch_source(u->backend_ioc,
G_IO_IN | G_IO_HUP,
- backend_read, dev, NULL, NULL);
+ backend_read, dev, NULL, ctxt);
if (reply_supported) {
msg.hdr.flags |= VHOST_USER_NEED_REPLY_MASK;
@@ -1981,6 +1993,42 @@ static int
vhost_user_postcopy_notifier(NotifierWithReturn *notifier,
return 0;
}
+static void *vhost_backend_channel_worker(void *opaque)
+{
+ struct backend_thread *backend_th = opaque;
+
+ rcu_register_thread();
+
+ backend_th->ctxt = g_main_context_new();
+ backend_th->loop = g_main_loop_new(backend_th->ctxt, false);
+ backend_th->thread_id = qemu_get_thread_id();
+
+ qemu_sem_post(&backend_th->init_done_sem);
+
+ g_main_loop_run(backend_th->loop);
+
+ g_main_loop_unref(backend_th->loop);
+ g_main_context_unref(backend_th->ctxt);
+ g_free(backend_th);
+ rcu_unregister_thread();
+ return NULL;
+}
+
+static void vhost_backend_thread_init(void)
+{
+ backend_th = g_malloc0(sizeof(struct backend_thread));
+ backend_th->thread_id = -1;
+ qemu_sem_init(&backend_th->init_done_sem, 0);
+
+ qemu_thread_create(&backend_th->thread, "backend-channel-worker",
+ vhost_backend_channel_worker, backend_th,
+ QEMU_THREAD_DETACHED);
+
+ while (backend_th->thread_id == -1) {
+ qemu_sem_wait(&backend_th->init_done_sem);
+ }
+}
+
static int vhost_user_backend_init(struct vhost_dev *dev, void *opaque,
Error **errp)
{
@@ -2108,10 +2156,17 @@ static int vhost_user_backend_init(struct vhost_dev
*dev, void *opaque,
}
if (dev->vq_index == 0) {
- err = vhost_setup_backend_channel(dev);
- if (err < 0) {
- error_setg_errno(errp, EPROTO, "vhost_backend_init failed");
- return -EPROTO;
+ if (!backend_thread_run) {
+ vhost_backend_thread_init();
+ backend_thread_run = true;
+ }
+
+ if (backend_thread_run && backend_th) {
+ err = vhost_setup_backend_channel(dev, backend_th->ctxt);
+ if (err < 0) {
+ error_setg_errno(errp, EPROTO, "vhost_backend_init failed");
+ return -EPROTO;
+ }
}
}
--
2.17.1
