From de25a5f05b76ca99299e09dabe04e7d59b9bed79 Mon Sep 17 00:00:00 2001
From: Kevin Wolf <kwolf@redhat.com>
Date: Mon, 12 Jul 2021 10:22:32 -0400
Subject: [PATCH 12/43] vhost-user: Fix backends without multiqueue support

RH-Author: Miroslav Rezanina <mrezanin@redhat.com>
RH-Bugzilla: 1957194

dev->max_queues was never initialised for backends that don't support
VHOST_USER_PROTOCOL_F_MQ, so it would use 0 as the maximum number of
queues to check against and consequently fail for any such backend.

Set it to 1 if the backend doesn't have multiqueue support.

Fixes: c90bd505a3e8210c23d69fecab9ee6f56ec4a161
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Message-Id: <20210705171429.29286-1-kwolf@redhat.com>
Reviewed-by: Cornelia Huck <cohuck@redhat.com>
Reviewed-by: Raphael Norwitz <raphael.norwitz@nutanix.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
(cherry picked from commit 84affad1fd4c5251d7cccf4df43b29e9157983a9)
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Signed-off-by: Danilo C. L. de Paula <ddepaula@redhat.com>
Signed-off-by: Miroslav Rezanina <mrezanin@redhat.com>
---
 hw/virtio/vhost-user.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/hw/virtio/vhost-user.c b/hw/virtio/vhost-user.c
index ee57abe045..53f50adcba 100644
--- a/hw/virtio/vhost-user.c
+++ b/hw/virtio/vhost-user.c
@@ -1908,7 +1908,10 @@ static int vhost_user_backend_init(struct vhost_dev *dev, void *opaque)
             if (err < 0) {
                 return err;
             }
+        } else {
+            dev->max_queues = 1;
         }
+
         if (dev->num_queues && dev->max_queues < dev->num_queues) {
             error_report("The maximum number of queues supported by the "
                          "backend is %" PRIu64, dev->max_queues);
-- 
2.27.0