diff mbox

[2/7] vhost-user: add protocol feature negotiation

Message ID 1442301035-7550-4-git-send-email-yuanhan.liu@linux.intel.com
State New
Headers show

Commit Message

Yuanhan Liu Sept. 15, 2015, 7:10 a.m. UTC
From: "Michael S. Tsirkin" <mst@redhat.com>

Support a separate bitmask for vhost-user protocol features,
and messages to get/set protocol features.

Invoke them at init.

No features are defined yet.

v2: leverage vhost_user_call for request handling -- Yuanhan Liu

Signed-off-by: Michael S. Tsirkin <address@hidden>
Signed-off-by: Yuanhan Liu <yuanhan.liu@linux.intel.com>
---
 docs/specs/vhost-user.txt | 37 +++++++++++++++++++++++++++++++++++++
 hw/net/vhost_net.c        |  2 ++
 hw/virtio/vhost-user.c    | 31 +++++++++++++++++++++++++++++++
 include/hw/virtio/vhost.h |  1 +
 4 files changed, 71 insertions(+)

Comments

Jason Wang Sept. 17, 2015, 7:12 a.m. UTC | #1
On 09/15/2015 03:10 PM, Yuanhan Liu wrote:
> From: "Michael S. Tsirkin" <mst@redhat.com>
>
> Support a separate bitmask for vhost-user protocol features,
> and messages to get/set protocol features.
>
> Invoke them at init.
>
> No features are defined yet.
>
> v2: leverage vhost_user_call for request handling -- Yuanhan Liu
>
> Signed-off-by: Michael S. Tsirkin <address@hidden>
> Signed-off-by: Yuanhan Liu <yuanhan.liu@linux.intel.com>
> ---
>  docs/specs/vhost-user.txt | 37 +++++++++++++++++++++++++++++++++++++
>  hw/net/vhost_net.c        |  2 ++
>  hw/virtio/vhost-user.c    | 31 +++++++++++++++++++++++++++++++
>  include/hw/virtio/vhost.h |  1 +
>  4 files changed, 71 insertions(+)
>
> diff --git a/docs/specs/vhost-user.txt b/docs/specs/vhost-user.txt
> index 650bb18..70da3b1 100644
> --- a/docs/specs/vhost-user.txt
> +++ b/docs/specs/vhost-user.txt
> @@ -113,6 +113,7 @@ message replies. Most of the requests don't require replies. Here is a list of
>  the ones that do:
>  
>   * VHOST_GET_FEATURES
> + * VHOST_GET_PROTOCOL_FEATURES
>   * VHOST_GET_VRING_BASE
>  
>  There are several messages that the master sends with file descriptors passed
> @@ -127,6 +128,13 @@ in the ancillary data:
>  If Master is unable to send the full message or receives a wrong reply it will
>  close the connection. An optional reconnection mechanism can be implemented.
>  
> +Any protocol extensions are gated by protocol feature bits,
> +which allows full backwards compatibility on both master
> +and slave.
> +As older slaves don't support negotiating protocol features,
> +a feature bit was dedicated for this purpose:
> +#define VHOST_USER_F_PROTOCOL_FEATURES 30
> +
>  Message types
>  -------------
>  
> @@ -138,6 +146,8 @@ Message types
>        Slave payload: u64
>  
>        Get from the underlying vhost implementation the features bitmask.
> +      Feature bit VHOST_USER_F_PROTOCOL_FEATURES signals slave support for
> +      VHOST_USER_GET_PROTOCOL_FEATURES and VHOST_USER_SET_PROTOCOL_FEATURES.
>  
>   * VHOST_USER_SET_FEATURES
>  
> @@ -146,6 +156,33 @@ Message types
>        Master payload: u64
>  
>        Enable features in the underlying vhost implementation using a bitmask.
> +      Feature bit VHOST_USER_F_PROTOCOL_FEATURES signals slave support for
> +      VHOST_USER_GET_PROTOCOL_FEATURES and VHOST_USER_SET_PROTOCOL_FEATURES.
> +
> + * VHOST_USER_GET_PROTOCOL_FEATURES
> +
> +      Id: 15
> +      Equivalent ioctl: VHOST_GET_FEATURES
> +      Master payload: N/A
> +      Slave payload: u64
> +
> +      Get the protocol feature bitmask from the underlying vhost implementation.
> +      Only legal if feature bit VHOST_USER_F_PROTOCOL_FEATURES is present in
> +      VHOST_USER_GET_FEATURES.
> +      Note: slave that reported VHOST_USER_F_PROTOCOL_FEATURES must support
> +      this message even before VHOST_USER_SET_FEATURES was called.
> +
> + * VHOST_USER_SET_PROTOCOL_FEATURES
> +
> +      Id: 16
> +      Ioctl: VHOST_SET_FEATURES
> +      Master payload: u64
> +
> +      Enable protocol features in the underlying vhost implementation.
> +      Only legal if feature bit VHOST_USER_F_PROTOCOL_FEATURES is present in
> +      VHOST_USER_GET_FEATURES.
> +      Note: slave that reported VHOST_USER_F_PROTOCOL_FEATURES must support
> +      this message even before VHOST_USER_SET_FEATURES was called.
>  
>   * VHOST_USER_SET_OWNER
>  
> diff --git a/hw/net/vhost_net.c b/hw/net/vhost_net.c
> index 5c1d11f..c864237 100644
> --- a/hw/net/vhost_net.c
> +++ b/hw/net/vhost_net.c
> @@ -152,8 +152,10 @@ struct vhost_net *vhost_net_init(VhostNetOptions *options)
>          net->dev.backend_features = qemu_has_vnet_hdr(options->net_backend)
>              ? 0 : (1ULL << VHOST_NET_F_VIRTIO_NET_HDR);
>          net->backend = r;
> +        net->dev.protocol_features = 0;
>      } else {
>          net->dev.backend_features = 0;
> +        net->dev.protocol_features = 0;
>          net->backend = -1;
>      }
>      net->nc = options->net_backend;
> diff --git a/hw/virtio/vhost-user.c b/hw/virtio/vhost-user.c
> index 13677ac..43169a1 100644
> --- a/hw/virtio/vhost-user.c
> +++ b/hw/virtio/vhost-user.c
> @@ -24,6 +24,8 @@
>  #include <linux/vhost.h>
>  
>  #define VHOST_MEMORY_MAX_NREGIONS    8
> +#define VHOST_USER_F_PROTOCOL_FEATURES 30
> +#define VHOST_USER_PROTOCOL_FEATURE_MASK 0x0ULL
>  
>  typedef enum VhostUserRequest {
>      VHOST_USER_NONE = 0,
> @@ -41,6 +43,8 @@ typedef enum VhostUserRequest {
>      VHOST_USER_SET_VRING_KICK = 12,
>      VHOST_USER_SET_VRING_CALL = 13,
>      VHOST_USER_SET_VRING_ERR = 14,
> +    VHOST_USER_GET_PROTOCOL_FEATURES = 15,
> +    VHOST_USER_SET_PROTOCOL_FEATURES = 16,
>      VHOST_USER_MAX
>  } VhostUserRequest;
>  
> @@ -206,11 +210,13 @@ static int vhost_user_call(struct vhost_dev *dev, unsigned long int request,
>  
>      switch (msg_request) {
>      case VHOST_USER_GET_FEATURES:
> +    case VHOST_USER_GET_PROTOCOL_FEATURES:
>          need_reply = 1;
>          break;
>  
>      case VHOST_USER_SET_FEATURES:
>      case VHOST_USER_SET_LOG_BASE:
> +    case VHOST_USER_SET_PROTOCOL_FEATURES:
>          msg.u64 = *((__u64 *) arg);
>          msg.size = sizeof(m.u64);
>          break;
> @@ -308,6 +314,7 @@ static int vhost_user_call(struct vhost_dev *dev, unsigned long int request,
>  
>          switch (msg_request) {
>          case VHOST_USER_GET_FEATURES:
> +        case VHOST_USER_GET_PROTOCOL_FEATURES:
>              if (msg.size != sizeof(m.u64)) {
>                  error_report("Received bad msg size.");
>                  return -1;
> @@ -333,10 +340,34 @@ static int vhost_user_call(struct vhost_dev *dev, unsigned long int request,
>  
>  static int vhost_user_init(struct vhost_dev *dev, void *opaque)
>  {
> +    unsigned long long features;
> +    int err;
> +
>      assert(dev->vhost_ops->backend_type == VHOST_BACKEND_TYPE_USER);
>  
>      dev->opaque = opaque;
>  
> +    err = vhost_user_call(dev, VHOST_USER_GET_FEATURES, &features);
> +    if (err < 0) {
> +        return err;
> +    }
> +
> +    if (__virtio_has_feature(features, VHOST_USER_F_PROTOCOL_FEATURES)) {

Need rebase to master. (And use virtio_has_feature() here).

> +        dev->backend_features |= 1ULL << VHOST_USER_F_PROTOCOL_FEATURES;
> +
> +        err = vhost_user_call(dev, VHOST_USER_GET_PROTOCOL_FEATURES, &features);
> +        if (err < 0) {
> +            return err;
> +        }
> +
> +        dev->protocol_features = features & VHOST_USER_PROTOCOL_FEATURE_MASK;
> +        err = vhost_user_call(dev, VHOST_USER_SET_PROTOCOL_FEATURES,
> +                              &dev->protocol_features);
> +        if (err < 0) {
> +            return err;
> +        }
> +    }
> +
>      return 0;
>  }
>  
> diff --git a/include/hw/virtio/vhost.h b/include/hw/virtio/vhost.h
> index dd51050..6467c73 100644
> --- a/include/hw/virtio/vhost.h
> +++ b/include/hw/virtio/vhost.h
> @@ -47,6 +47,7 @@ struct vhost_dev {
>      unsigned long long features;
>      unsigned long long acked_features;
>      unsigned long long backend_features;
> +    unsigned long long protocol_features;
>      bool started;
>      bool log_enabled;
>      unsigned long long log_size;
Yuanhan Liu Sept. 17, 2015, 7:20 a.m. UTC | #2
On Thu, Sep 17, 2015 at 03:12:55PM +0800, Jason Wang wrote:
> 
> 
> On 09/15/2015 03:10 PM, Yuanhan Liu wrote:
> > From: "Michael S. Tsirkin" <mst@redhat.com>
> >
> > Support a separate bitmask for vhost-user protocol features,
> > and messages to get/set protocol features.
> >
> > Invoke them at init.
> >
> > No features are defined yet.
> >
> > v2: leverage vhost_user_call for request handling -- Yuanhan Liu
> >
> > Signed-off-by: Michael S. Tsirkin <address@hidden>
> > Signed-off-by: Yuanhan Liu <yuanhan.liu@linux.intel.com>
> > ---
> >  docs/specs/vhost-user.txt | 37 +++++++++++++++++++++++++++++++++++++
> >  hw/net/vhost_net.c        |  2 ++
> >  hw/virtio/vhost-user.c    | 31 +++++++++++++++++++++++++++++++
> >  include/hw/virtio/vhost.h |  1 +
> >  4 files changed, 71 insertions(+)
> >
> > diff --git a/docs/specs/vhost-user.txt b/docs/specs/vhost-user.txt
> > index 650bb18..70da3b1 100644
> > --- a/docs/specs/vhost-user.txt
> > +++ b/docs/specs/vhost-user.txt
> > @@ -113,6 +113,7 @@ message replies. Most of the requests don't require replies. Here is a list of
> >  the ones that do:
> >  
> >   * VHOST_GET_FEATURES
> > + * VHOST_GET_PROTOCOL_FEATURES
> >   * VHOST_GET_VRING_BASE
> >  
> >  There are several messages that the master sends with file descriptors passed
> > @@ -127,6 +128,13 @@ in the ancillary data:
> >  If Master is unable to send the full message or receives a wrong reply it will
> >  close the connection. An optional reconnection mechanism can be implemented.
> >  
> > +Any protocol extensions are gated by protocol feature bits,
> > +which allows full backwards compatibility on both master
> > +and slave.
> > +As older slaves don't support negotiating protocol features,
> > +a feature bit was dedicated for this purpose:
> > +#define VHOST_USER_F_PROTOCOL_FEATURES 30
> > +
> >  Message types
> >  -------------
> >  
> > @@ -138,6 +146,8 @@ Message types
> >        Slave payload: u64
> >  
> >        Get from the underlying vhost implementation the features bitmask.
> > +      Feature bit VHOST_USER_F_PROTOCOL_FEATURES signals slave support for
> > +      VHOST_USER_GET_PROTOCOL_FEATURES and VHOST_USER_SET_PROTOCOL_FEATURES.
> >  
> >   * VHOST_USER_SET_FEATURES
> >  
> > @@ -146,6 +156,33 @@ Message types
> >        Master payload: u64
> >  
> >        Enable features in the underlying vhost implementation using a bitmask.
> > +      Feature bit VHOST_USER_F_PROTOCOL_FEATURES signals slave support for
> > +      VHOST_USER_GET_PROTOCOL_FEATURES and VHOST_USER_SET_PROTOCOL_FEATURES.
> > +
> > + * VHOST_USER_GET_PROTOCOL_FEATURES
> > +
> > +      Id: 15
> > +      Equivalent ioctl: VHOST_GET_FEATURES
> > +      Master payload: N/A
> > +      Slave payload: u64
> > +
> > +      Get the protocol feature bitmask from the underlying vhost implementation.
> > +      Only legal if feature bit VHOST_USER_F_PROTOCOL_FEATURES is present in
> > +      VHOST_USER_GET_FEATURES.
> > +      Note: slave that reported VHOST_USER_F_PROTOCOL_FEATURES must support
> > +      this message even before VHOST_USER_SET_FEATURES was called.
> > +
> > + * VHOST_USER_SET_PROTOCOL_FEATURES
> > +
> > +      Id: 16
> > +      Ioctl: VHOST_SET_FEATURES
> > +      Master payload: u64
> > +
> > +      Enable protocol features in the underlying vhost implementation.
> > +      Only legal if feature bit VHOST_USER_F_PROTOCOL_FEATURES is present in
> > +      VHOST_USER_GET_FEATURES.
> > +      Note: slave that reported VHOST_USER_F_PROTOCOL_FEATURES must support
> > +      this message even before VHOST_USER_SET_FEATURES was called.
> >  
> >   * VHOST_USER_SET_OWNER
> >  
> > diff --git a/hw/net/vhost_net.c b/hw/net/vhost_net.c
> > index 5c1d11f..c864237 100644
> > --- a/hw/net/vhost_net.c
> > +++ b/hw/net/vhost_net.c
> > @@ -152,8 +152,10 @@ struct vhost_net *vhost_net_init(VhostNetOptions *options)
> >          net->dev.backend_features = qemu_has_vnet_hdr(options->net_backend)
> >              ? 0 : (1ULL << VHOST_NET_F_VIRTIO_NET_HDR);
> >          net->backend = r;
> > +        net->dev.protocol_features = 0;
> >      } else {
> >          net->dev.backend_features = 0;
> > +        net->dev.protocol_features = 0;
> >          net->backend = -1;
> >      }
> >      net->nc = options->net_backend;
> > diff --git a/hw/virtio/vhost-user.c b/hw/virtio/vhost-user.c
> > index 13677ac..43169a1 100644
> > --- a/hw/virtio/vhost-user.c
> > +++ b/hw/virtio/vhost-user.c
> > @@ -24,6 +24,8 @@
> >  #include <linux/vhost.h>
> >  
> >  #define VHOST_MEMORY_MAX_NREGIONS    8
> > +#define VHOST_USER_F_PROTOCOL_FEATURES 30
> > +#define VHOST_USER_PROTOCOL_FEATURE_MASK 0x0ULL
> >  
> >  typedef enum VhostUserRequest {
> >      VHOST_USER_NONE = 0,
> > @@ -41,6 +43,8 @@ typedef enum VhostUserRequest {
> >      VHOST_USER_SET_VRING_KICK = 12,
> >      VHOST_USER_SET_VRING_CALL = 13,
> >      VHOST_USER_SET_VRING_ERR = 14,
> > +    VHOST_USER_GET_PROTOCOL_FEATURES = 15,
> > +    VHOST_USER_SET_PROTOCOL_FEATURES = 16,
> >      VHOST_USER_MAX
> >  } VhostUserRequest;
> >  
> > @@ -206,11 +210,13 @@ static int vhost_user_call(struct vhost_dev *dev, unsigned long int request,
> >  
> >      switch (msg_request) {
> >      case VHOST_USER_GET_FEATURES:
> > +    case VHOST_USER_GET_PROTOCOL_FEATURES:
> >          need_reply = 1;
> >          break;
> >  
> >      case VHOST_USER_SET_FEATURES:
> >      case VHOST_USER_SET_LOG_BASE:
> > +    case VHOST_USER_SET_PROTOCOL_FEATURES:
> >          msg.u64 = *((__u64 *) arg);
> >          msg.size = sizeof(m.u64);
> >          break;
> > @@ -308,6 +314,7 @@ static int vhost_user_call(struct vhost_dev *dev, unsigned long int request,
> >  
> >          switch (msg_request) {
> >          case VHOST_USER_GET_FEATURES:
> > +        case VHOST_USER_GET_PROTOCOL_FEATURES:
> >              if (msg.size != sizeof(m.u64)) {
> >                  error_report("Received bad msg size.");
> >                  return -1;
> > @@ -333,10 +340,34 @@ static int vhost_user_call(struct vhost_dev *dev, unsigned long int request,
> >  
> >  static int vhost_user_init(struct vhost_dev *dev, void *opaque)
> >  {
> > +    unsigned long long features;
> > +    int err;
> > +
> >      assert(dev->vhost_ops->backend_type == VHOST_BACKEND_TYPE_USER);
> >  
> >      dev->opaque = opaque;
> >  
> > +    err = vhost_user_call(dev, VHOST_USER_GET_FEATURES, &features);
> > +    if (err < 0) {
> > +        return err;
> > +    }
> > +
> > +    if (__virtio_has_feature(features, VHOST_USER_F_PROTOCOL_FEATURES)) {
> 
> Need rebase to master. (And use virtio_has_feature() here).

Thanks. Will fix them in next version.

	--yliu
diff mbox

Patch

diff --git a/docs/specs/vhost-user.txt b/docs/specs/vhost-user.txt
index 650bb18..70da3b1 100644
--- a/docs/specs/vhost-user.txt
+++ b/docs/specs/vhost-user.txt
@@ -113,6 +113,7 @@  message replies. Most of the requests don't require replies. Here is a list of
 the ones that do:
 
  * VHOST_GET_FEATURES
+ * VHOST_GET_PROTOCOL_FEATURES
  * VHOST_GET_VRING_BASE
 
 There are several messages that the master sends with file descriptors passed
@@ -127,6 +128,13 @@  in the ancillary data:
 If Master is unable to send the full message or receives a wrong reply it will
 close the connection. An optional reconnection mechanism can be implemented.
 
+Any protocol extensions are gated by protocol feature bits,
+which allows full backwards compatibility on both master
+and slave.
+As older slaves don't support negotiating protocol features,
+a feature bit was dedicated for this purpose:
+#define VHOST_USER_F_PROTOCOL_FEATURES 30
+
 Message types
 -------------
 
@@ -138,6 +146,8 @@  Message types
       Slave payload: u64
 
       Get from the underlying vhost implementation the features bitmask.
+      Feature bit VHOST_USER_F_PROTOCOL_FEATURES signals slave support for
+      VHOST_USER_GET_PROTOCOL_FEATURES and VHOST_USER_SET_PROTOCOL_FEATURES.
 
  * VHOST_USER_SET_FEATURES
 
@@ -146,6 +156,33 @@  Message types
       Master payload: u64
 
       Enable features in the underlying vhost implementation using a bitmask.
+      Feature bit VHOST_USER_F_PROTOCOL_FEATURES signals slave support for
+      VHOST_USER_GET_PROTOCOL_FEATURES and VHOST_USER_SET_PROTOCOL_FEATURES.
+
+ * VHOST_USER_GET_PROTOCOL_FEATURES
+
+      Id: 15
+      Equivalent ioctl: VHOST_GET_FEATURES
+      Master payload: N/A
+      Slave payload: u64
+
+      Get the protocol feature bitmask from the underlying vhost implementation.
+      Only legal if feature bit VHOST_USER_F_PROTOCOL_FEATURES is present in
+      VHOST_USER_GET_FEATURES.
+      Note: slave that reported VHOST_USER_F_PROTOCOL_FEATURES must support
+      this message even before VHOST_USER_SET_FEATURES was called.
+
+ * VHOST_USER_SET_PROTOCOL_FEATURES
+
+      Id: 16
+      Ioctl: VHOST_SET_FEATURES
+      Master payload: u64
+
+      Enable protocol features in the underlying vhost implementation.
+      Only legal if feature bit VHOST_USER_F_PROTOCOL_FEATURES is present in
+      VHOST_USER_GET_FEATURES.
+      Note: slave that reported VHOST_USER_F_PROTOCOL_FEATURES must support
+      this message even before VHOST_USER_SET_FEATURES was called.
 
  * VHOST_USER_SET_OWNER
 
diff --git a/hw/net/vhost_net.c b/hw/net/vhost_net.c
index 5c1d11f..c864237 100644
--- a/hw/net/vhost_net.c
+++ b/hw/net/vhost_net.c
@@ -152,8 +152,10 @@  struct vhost_net *vhost_net_init(VhostNetOptions *options)
         net->dev.backend_features = qemu_has_vnet_hdr(options->net_backend)
             ? 0 : (1ULL << VHOST_NET_F_VIRTIO_NET_HDR);
         net->backend = r;
+        net->dev.protocol_features = 0;
     } else {
         net->dev.backend_features = 0;
+        net->dev.protocol_features = 0;
         net->backend = -1;
     }
     net->nc = options->net_backend;
diff --git a/hw/virtio/vhost-user.c b/hw/virtio/vhost-user.c
index 13677ac..43169a1 100644
--- a/hw/virtio/vhost-user.c
+++ b/hw/virtio/vhost-user.c
@@ -24,6 +24,8 @@ 
 #include <linux/vhost.h>
 
 #define VHOST_MEMORY_MAX_NREGIONS    8
+#define VHOST_USER_F_PROTOCOL_FEATURES 30
+#define VHOST_USER_PROTOCOL_FEATURE_MASK 0x0ULL
 
 typedef enum VhostUserRequest {
     VHOST_USER_NONE = 0,
@@ -41,6 +43,8 @@  typedef enum VhostUserRequest {
     VHOST_USER_SET_VRING_KICK = 12,
     VHOST_USER_SET_VRING_CALL = 13,
     VHOST_USER_SET_VRING_ERR = 14,
+    VHOST_USER_GET_PROTOCOL_FEATURES = 15,
+    VHOST_USER_SET_PROTOCOL_FEATURES = 16,
     VHOST_USER_MAX
 } VhostUserRequest;
 
@@ -206,11 +210,13 @@  static int vhost_user_call(struct vhost_dev *dev, unsigned long int request,
 
     switch (msg_request) {
     case VHOST_USER_GET_FEATURES:
+    case VHOST_USER_GET_PROTOCOL_FEATURES:
         need_reply = 1;
         break;
 
     case VHOST_USER_SET_FEATURES:
     case VHOST_USER_SET_LOG_BASE:
+    case VHOST_USER_SET_PROTOCOL_FEATURES:
         msg.u64 = *((__u64 *) arg);
         msg.size = sizeof(m.u64);
         break;
@@ -308,6 +314,7 @@  static int vhost_user_call(struct vhost_dev *dev, unsigned long int request,
 
         switch (msg_request) {
         case VHOST_USER_GET_FEATURES:
+        case VHOST_USER_GET_PROTOCOL_FEATURES:
             if (msg.size != sizeof(m.u64)) {
                 error_report("Received bad msg size.");
                 return -1;
@@ -333,10 +340,34 @@  static int vhost_user_call(struct vhost_dev *dev, unsigned long int request,
 
 static int vhost_user_init(struct vhost_dev *dev, void *opaque)
 {
+    unsigned long long features;
+    int err;
+
     assert(dev->vhost_ops->backend_type == VHOST_BACKEND_TYPE_USER);
 
     dev->opaque = opaque;
 
+    err = vhost_user_call(dev, VHOST_USER_GET_FEATURES, &features);
+    if (err < 0) {
+        return err;
+    }
+
+    if (__virtio_has_feature(features, VHOST_USER_F_PROTOCOL_FEATURES)) {
+        dev->backend_features |= 1ULL << VHOST_USER_F_PROTOCOL_FEATURES;
+
+        err = vhost_user_call(dev, VHOST_USER_GET_PROTOCOL_FEATURES, &features);
+        if (err < 0) {
+            return err;
+        }
+
+        dev->protocol_features = features & VHOST_USER_PROTOCOL_FEATURE_MASK;
+        err = vhost_user_call(dev, VHOST_USER_SET_PROTOCOL_FEATURES,
+                              &dev->protocol_features);
+        if (err < 0) {
+            return err;
+        }
+    }
+
     return 0;
 }
 
diff --git a/include/hw/virtio/vhost.h b/include/hw/virtio/vhost.h
index dd51050..6467c73 100644
--- a/include/hw/virtio/vhost.h
+++ b/include/hw/virtio/vhost.h
@@ -47,6 +47,7 @@  struct vhost_dev {
     unsigned long long features;
     unsigned long long acked_features;
     unsigned long long backend_features;
+    unsigned long long protocol_features;
     bool started;
     bool log_enabled;
     unsigned long long log_size;