From 963b02764537c66af88b82bd297c375b147e0756 Mon Sep 17 00:00:00 2001 From: yaozhenguo Date: Fri, 11 Oct 2024 18:29:13 +0800 Subject: virtio/vhost-user: fix qemu abort when hotunplug vhost-user-net device During the hot-unplugging of vhost-user-net type network cards, the vhost_user_cleanup function may add the same rcu node to the rcu linked list. The function call in this case is as follows: vhost_user_cleanup ->vhost_user_host_notifier_remove ->call_rcu(n, vhost_user_host_notifier_free, rcu); ->g_free_rcu(n, rcu); When this happens, QEMU will abort in try_dequeue: if (head == &dummy && qatomic_mb_read(&tail) == &dummy.next) { abort(); } backtrace is as follows: 0 __pthread_kill_implementation () at /usr/lib64/libc.so.6 1 raise () at /usr/lib64/libc.so.6 2 abort () at /usr/lib64/libc.so.6 3 try_dequeue () at ../util/rcu.c:235 4 call_rcu_thread (0) at ../util/rcu.c:288 5 qemu_thread_start (0) at ../util/qemu-thread-posix.c:541 6 start_thread () at /usr/lib64/libc.so.6 7 clone3 () at /usr/lib64/libc.so.6 The reason for the abort is that adding two identical nodes to the rcu linked list will cause the rcu linked list to become a ring, but when the dummy node is added after the two identical nodes, the ring is opened. But only one node is added to list with rcu_call_count added twice. This will cause rcu try_dequeue abort. This happens when n->addr != 0. In some scenarios, this does happen. For example, this situation will occur when using a 32-queue DPU vhost-user-net type network card for hot-unplug testing, because VhostUserHostNotifier->addr will be cleared during the processing of VHOST_USER_BACKEND_VRING_HOST_NOTIFIER_MSG. However,it is asynchronous, so we cannot guarantee that VhostUserHostNotifier->addr is zero in vhost_user_cleanup. Therefore, it is necessary to merge g_free_rcu and vhost_user_host_notifier_free into one rcu node. Fixes: 503e355465 ("virtio/vhost-user: dynamically assign VhostUserHostNotifiers") Signed-off-by: yaozhenguo Message-Id: <20241011102913.45582-1-yaozhenguo@jd.com> Reviewed-by: Stefano Garzarella Reviewed-by: Michael S. Tsirkin Signed-off-by: Michael S. Tsirkin --- include/hw/virtio/vhost-user.h | 1 + 1 file changed, 1 insertion(+) (limited to 'include/hw/virtio/vhost-user.h') diff --git a/include/hw/virtio/vhost-user.h b/include/hw/virtio/vhost-user.h index 324cd8663a..9a3f238b43 100644 --- a/include/hw/virtio/vhost-user.h +++ b/include/hw/virtio/vhost-user.h @@ -54,6 +54,7 @@ typedef struct VhostUserHostNotifier { void *addr; void *unmap_addr; int idx; + bool destroy; } VhostUserHostNotifier; /** -- cgit v1.2.3