vhost: fix deadlock on IOTLB miss

[dpdk.git] / lib / librte_vhost / vhost.c

diff --git a/lib/librte_vhost/vhost.c b/lib/librte_vhost/vhost.c
index 54a1864..4f8b73a 100644 (file)
--- a/lib/librte_vhost/vhost.c
+++ b/lib/librte_vhost/vhost.c
@@ -55,6 +55,7 @@
 
 struct virtio_net *vhost_devices[MAX_VHOST_DEVICE];
 
+/* Called with iotlb_lock read-locked */
 uint64_t
 __vhost_iova_to_vva(struct virtio_net *dev, struct vhost_virtqueue *vq,
                    uint64_t iova, uint64_t size, uint8_t perm)
@@ -71,8 +72,19 @@ __vhost_iova_to_vva(struct virtio_net *dev, struct vhost_virtqueue *vq,
                return vva;
 
        if (!vhost_user_iotlb_pending_miss(vq, iova + tmp_size, perm)) {
+               /*
+                * iotlb_lock is read-locked for a full burst,
+                * but it only protects the iotlb cache.
+                * In case of IOTLB miss, we might block on the socket,
+                * which could cause a deadlock with QEMU if an IOTLB update
+                * is being handled. We can safely unlock here to avoid it.
+                */
+               vhost_user_iotlb_rd_unlock(vq);
+
                vhost_user_iotlb_pending_insert(vq, iova + tmp_size, perm);
                vhost_user_iotlb_miss(dev, iova + tmp_size, perm);
+
+               vhost_user_iotlb_rd_lock(vq);
        }
 
        return 0;