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>

vhost-user-quit-infinite-loop-while-used-memslots-is.patch

@@ -0,0 +1,88 @@
+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
+