From 90d4333d4bbde45a10892bf9004979d239d39e28 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         | 10 ++++++++++
 include/hw/virtio/vhost.h |  1 +
 net/vhost-user.c          |  5 +++++
 3 files changed, 16 insertions(+)

diff --git a/hw/virtio/vhost.c b/hw/virtio/vhost.c
index a8adc149ad..038ac37dd0 100644
--- a/hw/virtio/vhost.c
+++ b/hw/virtio/vhost.c
@@ -56,6 +56,8 @@ static unsigned int used_shared_memslots;
 static QLIST_HEAD(, vhost_dev) vhost_devices =
     QLIST_HEAD_INITIALIZER(vhost_devices);
 
+bool used_memslots_exceeded;
+
 unsigned int vhost_get_max_memslots(void)
 {
     unsigned int max = UINT_MAX;
@@ -1569,8 +1571,11 @@ int vhost_dev_init(struct vhost_dev *hdev, void *opaque,
         error_setg(errp, "vhost backend memory slots limit (%d) is less"
                    " than current number of used (%d) and reserved (%d)"
                    " memory slots for memory devices.", limit, used, reserved);
+        used_memslots_exceeded = true;
         r = -EINVAL;
         goto fail_busyloop;
+    } else {
+        used_memslots_exceeded = false;
     }
 
     return 0;
@@ -2405,3 +2410,8 @@ fail:
 
     return ret;
 }
+
+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 02477788df..444ca0ad42 100644
--- a/include/hw/virtio/vhost.h
+++ b/include/hw/virtio/vhost.h
@@ -340,6 +340,7 @@ 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);
 bool vhost_dev_has_iommu(struct vhost_dev *dev);
 
 #ifdef CONFIG_VHOST
diff --git a/net/vhost-user.c b/net/vhost-user.c
index 51fa8c678f..86fd5056ab 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)
 
@@ -373,6 +374,10 @@ 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