From f46191f24706a6200cfe607a902b3da45f57c9ad Mon Sep 17 00:00:00 2001
From: Jinhua Cao <caojinhua1@huawei.com>
Date: Fri, 11 Feb 2022 19:24:30 +0800
Subject: [PATCH] vhost-user: quit infinite loop while used memslots is more
 than the backend limit

When used memslots is more than the backend limit,
the vhost-user netcard would attach fail and quit
infinite loop.

Signed-off-by: Jinhua Cao <caojinhua1@huawei.com>
---
 hw/virtio/vhost.c         | 9 +++++++++
 include/hw/virtio/vhost.h | 1 +
 net/vhost-user.c          | 6 ++++++
 3 files changed, 16 insertions(+)

diff --git a/hw/virtio/vhost.c b/hw/virtio/vhost.c
index e4809777bc..4c4072951c 100644
--- a/hw/virtio/vhost.c
+++ b/hw/virtio/vhost.c
@@ -48,6 +48,8 @@ static struct vhost_log *vhost_log_shm;
 static QLIST_HEAD(, vhost_dev) vhost_devices =
     QLIST_HEAD_INITIALIZER(vhost_devices);
 
+bool used_memslots_exceeded;
+
 bool vhost_has_free_slot(void)
 {
     struct vhost_dev *hdev;
@@ -1336,9 +1338,11 @@ static bool vhost_dev_used_memslots_is_exceeded(struct vhost_dev *hdev)
         hdev->vhost_ops->vhost_backend_memslots_limit(hdev)) {
         error_report("vhost backend memory slots limit is less"
                 " than current number of present memory slots");
+	used_memslots_exceeded = true;
         return true;
     }
 
+    used_memslots_exceeded = false;
     return false;
 }
 
@@ -1895,3 +1899,8 @@ int vhost_net_set_backend(struct vhost_dev *hdev,
 
     return -1;
 }
+
+bool used_memslots_is_exceeded(void)
+{
+    return used_memslots_exceeded;
+}
diff --git a/include/hw/virtio/vhost.h b/include/hw/virtio/vhost.h
index 58a73e7b7a..86f36f0106 100644
--- a/include/hw/virtio/vhost.h
+++ b/include/hw/virtio/vhost.h
@@ -154,4 +154,5 @@ int vhost_dev_set_inflight(struct vhost_dev *dev,
                            struct vhost_inflight *inflight);
 int vhost_dev_get_inflight(struct vhost_dev *dev, uint16_t queue_size,
                            struct vhost_inflight *inflight);
+bool used_memslots_is_exceeded(void);
 #endif
diff --git a/net/vhost-user.c b/net/vhost-user.c
index d1aefcb9aa..f910a286e4 100644
--- a/net/vhost-user.c
+++ b/net/vhost-user.c
@@ -20,6 +20,7 @@
 #include "qemu/error-report.h"
 #include "qemu/option.h"
 #include "trace.h"
+#include "include/hw/virtio/vhost.h"
 
 #define VHOST_USER_RECONNECT_TIME (3)
 
@@ -369,6 +370,11 @@ static int net_vhost_user_init(NetClientState *peer, const char *device,
         qemu_chr_fe_set_handlers(&s->chr, NULL, NULL,
                                  net_vhost_user_event, NULL, nc0->name, NULL,
                                  true);
+        if (used_memslots_is_exceeded()) {
+            error_report("used memslots exceeded the backend limit, quit "
+                            "loop");
+            goto err;
+        }
     } while (!s->started);
 
     assert(s->vhost_net);
-- 
2.27.0