4 files changed, 38 insertions, 9 deletions

diff --git a/hw/block/vhost-user-blk.c b/hw/block/vhost-user-blk.c
index f840f07dfe..262baca432 100644
--- a/hw/block/vhost-user-blk.c
+++ b/hw/block/vhost-user-blk.c
@@ -259,6 +259,8 @@ static void vhost_user_blk_device_realize(DeviceState *dev, Error **errp)
     s->dev.vq_index = 0;
     s->dev.backend_features = 0;
 
+    vhost_dev_set_config_notifier(&s->dev, &blk_ops);
+
     ret = vhost_dev_init(&s->dev, &s->chardev, VHOST_BACKEND_TYPE_USER, 0);
     if (ret < 0) {
         error_setg(errp, "vhost-user-blk: vhost initialization failed: %s",
@@ -277,8 +279,6 @@ static void vhost_user_blk_device_realize(DeviceState *dev, Error **errp)
         s->blkcfg.num_queues = s->num_queues;
     }
 
-    vhost_dev_set_config_notifier(&s->dev, &blk_ops);
-
     return;
 
 vhost_err:
diff --git a/hw/char/virtio-serial-bus.c b/hw/char/virtio-serial-bus.c
index 9470bd7be7..d2dd8ab502 100644
--- a/hw/char/virtio-serial-bus.c
+++ b/hw/char/virtio-serial-bus.c
@@ -580,13 +580,16 @@ static void set_config(VirtIODevice *vdev, const uint8_t *config_data)
     VirtIOSerial *vser = VIRTIO_SERIAL(vdev);
     struct virtio_console_config *config =
         (struct virtio_console_config *)config_data;
-    uint8_t emerg_wr_lo = le32_to_cpu(config->emerg_wr);
     VirtIOSerialPort *port = find_first_connected_console(vser);
     VirtIOSerialPortClass *vsc;
+    uint8_t emerg_wr_lo;
 
-    if (!config->emerg_wr) {
+    if (!virtio_has_feature(vser->host_features,
+        VIRTIO_CONSOLE_F_EMERG_WRITE) || !config->emerg_wr) {
         return;
     }
+
+    emerg_wr_lo = le32_to_cpu(config->emerg_wr);
     /* Make sure we don't misdetect an emergency write when the guest
      * does a short config write after an emergency write. */
     config->emerg_wr = 0;
diff --git a/hw/virtio/vhost-user.c b/hw/virtio/vhost-user.c
index 44aea5c0a8..38da8692bb 100644
--- a/hw/virtio/vhost-user.c
+++ b/hw/virtio/vhost-user.c
@@ -46,6 +46,7 @@ enum VhostUserProtocolFeature {
     VHOST_USER_PROTOCOL_F_CROSS_ENDIAN = 6,
     VHOST_USER_PROTOCOL_F_CRYPTO_SESSION = 7,
     VHOST_USER_PROTOCOL_F_PAGEFAULT = 8,
+    VHOST_USER_PROTOCOL_F_CONFIG = 9,
     VHOST_USER_PROTOCOL_F_MAX
 };
 
@@ -1211,6 +1212,17 @@ static int vhost_user_init(struct vhost_dev *dev, void *opaque)
 
         dev->protocol_features =
             protocol_features & VHOST_USER_PROTOCOL_FEATURE_MASK;
+
+        if (!dev->config_ops || !dev->config_ops->vhost_dev_config_notifier) {
+            /* Don't acknowledge CONFIG feature if device doesn't support it */
+            dev->protocol_features &= ~(1ULL << VHOST_USER_PROTOCOL_F_CONFIG);
+        } else if (!(protocol_features &
+                    (1ULL << VHOST_USER_PROTOCOL_F_CONFIG))) {
+            error_report("Device expects VHOST_USER_PROTOCOL_F_CONFIG "
+                    "but backend does not support it.");
+            return -1;
+        }
+
         err = vhost_user_set_protocol_features(dev, dev->protocol_features);
         if (err < 0) {
             return err;
@@ -1405,6 +1417,11 @@ static int vhost_user_get_config(struct vhost_dev *dev, uint8_t *config,
         .hdr.size = VHOST_USER_CONFIG_HDR_SIZE + config_len,
     };
 
+    if (!virtio_has_feature(dev->protocol_features,
+                VHOST_USER_PROTOCOL_F_CONFIG)) {
+        return -1;
+    }
+
     if (config_len > VHOST_USER_MAX_CONFIG_SIZE) {
         return -1;
     }
@@ -1448,6 +1465,11 @@ static int vhost_user_set_config(struct vhost_dev *dev, const uint8_t *data,
         .hdr.size = VHOST_USER_CONFIG_HDR_SIZE + size,
     };
 
+    if (!virtio_has_feature(dev->protocol_features,
+                VHOST_USER_PROTOCOL_F_CONFIG)) {
+        return -1;
+    }
+
     if (reply_supported) {
         msg.hdr.flags |= VHOST_USER_NEED_REPLY_MASK;
     }
diff --git a/hw/virtio/vhost.c b/hw/virtio/vhost.c
index 250f886acb..a21a5a2ca1 100644
--- a/hw/virtio/vhost.c
+++ b/hw/virtio/vhost.c
@@ -595,10 +595,15 @@ static void vhost_region_add_section(struct vhost_dev *dev,
                                         prev_sec->offset_within_address_space,
                                         prev_sec->offset_within_region);
             } else {
-                error_report("%s: Overlapping but not coherent sections "
-                             "at %"PRIx64,
-                             __func__, mrs_gpa);
-                return;
+                /* adjoining regions are fine, but overlapping ones with
+                 * different blocks/offsets shouldn't happen
+                 */
+                if (mrs_gpa != prev_gpa_end + 1) {
+                    error_report("%s: Overlapping but not coherent sections "
+                                 "at %"PRIx64,
+                                 __func__, mrs_gpa);
+                    return;
+                }
             }
         }
     }
@@ -1451,7 +1456,6 @@ int vhost_dev_set_config(struct vhost_dev *hdev, const uint8_t *data,
 void vhost_dev_set_config_notifier(struct vhost_dev *hdev,
                                    const VhostDevConfigOps *ops)
 {
-    assert(hdev->vhost_ops);
     hdev->config_ops = ops;
 }