vhost allocates a message node whenever address translation misses. If
userspace reads these messages without resolving them, repeated virtqueue
kicks can grow the pending message list until the host runs out of memory.
Virtqueue processing stops at the first translation miss and cannot make
progress until userspace installs a mapping. Keep a pointer to that
outstanding message in the virtqueue and suppress additional misses until
the node is resolved or discarded.
The pointer remains set while the message is queued for reading, copied to
userspace, or waiting on the pending list. Clear it under the IOTLB lock
when the owning node is freed. This bounds outstanding miss messages by the
fixed number of virtqueues without introducing an arbitrary queue limit.
Signed-off-by: Linfeng Sun <linfeng.sun.dev@gmail.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Message-ID: <20260903-fix-kernel-panic-in-vhost_iotlb_miss_pending_list-v1-1-39b8cd427978@gmail.com>
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