[PATCH 3/4] vhost: add method vhost_set_vring_err

[Konstantin Khlebnikov <khlebnikov@yandex-team.ru>]

Kernel and user vhost may report virtqueue errors via eventfd.
This is only reliable way to get notification about protocol error.

Signed-off-by: Konstantin Khlebnikov <khlebnikov@yandex-team.ru>
---
 hw/virtio/vhost-backend.c         |    7 +++++++
 hw/virtio/vhost-user.c            |    6 ++++++
 include/hw/virtio/vhost-backend.h |    3 +++
 3 files changed, 16 insertions(+)

diff --git a/hw/virtio/vhost-backend.c b/hw/virtio/vhost-backend.c
index 4de8b6b3b0..8e581575c9 100644
--- a/hw/virtio/vhost-backend.c
+++ b/hw/virtio/vhost-backend.c
@@ -146,6 +146,12 @@ static int vhost_kernel_set_vring_call(struct vhost_dev *dev,
     return vhost_kernel_call(dev, VHOST_SET_VRING_CALL, file);
 }
 
+static int vhost_kernel_set_vring_err(struct vhost_dev *dev,
+                                      struct vhost_vring_file *file)
+{
+    return vhost_kernel_call(dev, VHOST_SET_VRING_ERR, file);
+}
+
 static int vhost_kernel_set_vring_busyloop_timeout(struct vhost_dev *dev,
                                                    struct vhost_vring_state *s)
 {
@@ -309,6 +315,7 @@ const VhostOps kernel_ops = {
         .vhost_get_vring_base = vhost_kernel_get_vring_base,
         .vhost_set_vring_kick = vhost_kernel_set_vring_kick,
         .vhost_set_vring_call = vhost_kernel_set_vring_call,
+        .vhost_set_vring_err = vhost_kernel_set_vring_err,
         .vhost_set_vring_busyloop_timeout =
                                 vhost_kernel_set_vring_busyloop_timeout,
         .vhost_set_features = vhost_kernel_set_features,
diff --git a/hw/virtio/vhost-user.c b/hw/virtio/vhost-user.c
index b040c1ad2b..37f8d4ab6f 100644
--- a/hw/virtio/vhost-user.c
+++ b/hw/virtio/vhost-user.c
@@ -1313,6 +1313,11 @@ static int vhost_user_set_vring_call(struct vhost_dev *dev,
     return vhost_set_vring_file(dev, VHOST_USER_SET_VRING_CALL, file);
 }
 
+static int vhost_user_set_vring_err(struct vhost_dev *dev,
+                                    struct vhost_vring_file *file)
+{
+    return vhost_set_vring_file(dev, VHOST_USER_SET_VRING_ERR, file);
+}
 
 static int vhost_user_get_u64(struct vhost_dev *dev, int request, uint64_t *u64)
 {
@@ -2618,6 +2623,7 @@ const VhostOps user_ops = {
         .vhost_get_vring_base = vhost_user_get_vring_base,
         .vhost_set_vring_kick = vhost_user_set_vring_kick,
         .vhost_set_vring_call = vhost_user_set_vring_call,
+        .vhost_set_vring_err = vhost_user_set_vring_err,
         .vhost_set_features = vhost_user_set_features,
         .vhost_get_features = vhost_user_get_features,
         .vhost_set_owner = vhost_user_set_owner,
diff --git a/include/hw/virtio/vhost-backend.h b/include/hw/virtio/vhost-backend.h
index 81bf3109f8..eab46d7f0b 100644
--- a/include/hw/virtio/vhost-backend.h
+++ b/include/hw/virtio/vhost-backend.h
@@ -69,6 +69,8 @@ typedef int (*vhost_set_vring_kick_op)(struct vhost_dev *dev,
                                        struct vhost_vring_file *file);
 typedef int (*vhost_set_vring_call_op)(struct vhost_dev *dev,
                                        struct vhost_vring_file *file);
+typedef int (*vhost_set_vring_err_op)(struct vhost_dev *dev,
+                                      struct vhost_vring_file *file);
 typedef int (*vhost_set_vring_busyloop_timeout_op)(struct vhost_dev *dev,
                                                    struct vhost_vring_state *r);
 typedef int (*vhost_set_features_op)(struct vhost_dev *dev,
@@ -145,6 +147,7 @@ typedef struct VhostOps {
     vhost_get_vring_base_op vhost_get_vring_base;
     vhost_set_vring_kick_op vhost_set_vring_kick;
     vhost_set_vring_call_op vhost_set_vring_call;
+    vhost_set_vring_err_op vhost_set_vring_err;
     vhost_set_vring_busyloop_timeout_op vhost_set_vring_busyloop_timeout;
     vhost_set_features_op vhost_set_features;
     vhost_get_features_op vhost_get_features;