vhost_user_get_config() can fail without setting an error.  Unclean.
Its caller vhost_dev_get_config() compensates by substituting a
generic error then.  Goes back to commit 50de51387f "vhost:
Distinguish errors in vhost_dev_get_config()".

Clean up by moving the generic error from vhost_dev_get_config() to
all the failure paths that neglect to set an error.

Cc: Kevin Wolf <kwolf@redhat.com>
Cc: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Markus Armbruster <armbru@redhat.com>
---
 hw/virtio/vhost-user.c |  2 ++
 hw/virtio/vhost.c      | 10 ++--------
 2 files changed, 4 insertions(+), 8 deletions(-)

diff --git a/hw/virtio/vhost-user.c b/hw/virtio/vhost-user.c
index 29ea2b4fce..dbbd6fbc25 100644
--- a/hw/virtio/vhost-user.c
+++ b/hw/virtio/vhost-user.c
@@ -2139,10 +2139,12 @@ static int vhost_user_get_config(struct vhost_dev *dev, uint8_t *config,
     msg.payload.config.offset = 0;
     msg.payload.config.size = config_len;
     if (vhost_user_write(dev, &msg, NULL, 0) < 0) {
+        error_setg_errno(errp, -EPROTO, "vhost_get_config failed");
         return -EPROTO;
     }
 
     if (vhost_user_read(dev, &msg) < 0) {
+        error_setg_errno(errp, -EPROTO, "vhost_get_config failed");
         return -EPROTO;
     }
 
diff --git a/hw/virtio/vhost.c b/hw/virtio/vhost.c
index dbbc6b6915..88f8a397dc 100644
--- a/hw/virtio/vhost.c
+++ b/hw/virtio/vhost.c
@@ -1564,17 +1564,11 @@ void vhost_ack_features(struct vhost_dev *hdev, const int *feature_bits,
 int vhost_dev_get_config(struct vhost_dev *hdev, uint8_t *config,
                          uint32_t config_len, Error **errp)
 {
-    ERRP_GUARD();
-    int ret;
-
     assert(hdev->vhost_ops);
 
     if (hdev->vhost_ops->vhost_get_config) {
-        ret = hdev->vhost_ops->vhost_get_config(hdev, config, config_len, errp);
-        if (ret < 0 && !*errp) {
-            error_setg_errno(errp, -ret, "vhost_get_config failed");
-        }
-        return ret;
+        return hdev->vhost_ops->vhost_get_config(hdev, config, config_len,
+                                                 errp);
     }
 
     error_setg(errp, "vhost_get_config not implemented");
-- 
2.31.1

On 7/20/21 2:54 PM, Markus Armbruster wrote:
> vhost_user_get_config() can fail without setting an error.  Unclean.
> Its caller vhost_dev_get_config() compensates by substituting a
> generic error then.  Goes back to commit 50de51387f "vhost:
> Distinguish errors in vhost_dev_get_config()".
> 
> Clean up by moving the generic error from vhost_dev_get_config() to
> all the failure paths that neglect to set an error.
> 
> Cc: Kevin Wolf <kwolf@redhat.com>
> Cc: Michael S. Tsirkin <mst@redhat.com>
> Signed-off-by: Markus Armbruster <armbru@redhat.com>
> ---
>  hw/virtio/vhost-user.c |  2 ++
>  hw/virtio/vhost.c      | 10 ++--------
>  2 files changed, 4 insertions(+), 8 deletions(-)

Reviewed-by: Philippe Mathieu-Daudé <philmd@redhat.com>

On 7/20/21 2:54 PM, Markus Armbruster wrote:
> vhost_user_get_config() can fail without setting an error.  Unclean.
> Its caller vhost_dev_get_config() compensates by substituting a
> generic error then.  Goes back to commit 50de51387f "vhost:
> Distinguish errors in vhost_dev_get_config()".
> 
> Clean up by moving the generic error from vhost_dev_get_config() to
> all the failure paths that neglect to set an error.
> 
> Cc: Kevin Wolf <kwolf@redhat.com>
> Cc: Michael S. Tsirkin <mst@redhat.com>
> Signed-off-by: Markus Armbruster <armbru@redhat.com>
> ---
>  hw/virtio/vhost-user.c |  2 ++
>  hw/virtio/vhost.c      | 10 ++--------
>  2 files changed, 4 insertions(+), 8 deletions(-)
> 
> diff --git a/hw/virtio/vhost-user.c b/hw/virtio/vhost-user.c
> index 29ea2b4fce..dbbd6fbc25 100644
> --- a/hw/virtio/vhost-user.c
> +++ b/hw/virtio/vhost-user.c
> @@ -2139,10 +2139,12 @@ static int vhost_user_get_config(struct vhost_dev *dev, uint8_t *config,
>      msg.payload.config.offset = 0;
>      msg.payload.config.size = config_len;
>      if (vhost_user_write(dev, &msg, NULL, 0) < 0) {
> +        error_setg_errno(errp, -EPROTO, "vhost_get_config failed");
>          return -EPROTO;
>      }
>  
>      if (vhost_user_read(dev, &msg) < 0) {
> +        error_setg_errno(errp, -EPROTO, "vhost_get_config failed");
>          return -EPROTO;
>      }

Oops, should be error_setg_errno(EPROTO)!

Philippe Mathieu-Daudé <philmd@redhat.com> writes:

> On 7/20/21 2:54 PM, Markus Armbruster wrote:
>> vhost_user_get_config() can fail without setting an error.  Unclean.
>> Its caller vhost_dev_get_config() compensates by substituting a
>> generic error then.  Goes back to commit 50de51387f "vhost:
>> Distinguish errors in vhost_dev_get_config()".
>> 
>> Clean up by moving the generic error from vhost_dev_get_config() to
>> all the failure paths that neglect to set an error.
>> 
>> Cc: Kevin Wolf <kwolf@redhat.com>
>> Cc: Michael S. Tsirkin <mst@redhat.com>
>> Signed-off-by: Markus Armbruster <armbru@redhat.com>
>> ---
>>  hw/virtio/vhost-user.c |  2 ++
>>  hw/virtio/vhost.c      | 10 ++--------
>>  2 files changed, 4 insertions(+), 8 deletions(-)
>> 
>> diff --git a/hw/virtio/vhost-user.c b/hw/virtio/vhost-user.c
>> index 29ea2b4fce..dbbd6fbc25 100644
>> --- a/hw/virtio/vhost-user.c
>> +++ b/hw/virtio/vhost-user.c
>> @@ -2139,10 +2139,12 @@ static int vhost_user_get_config(struct vhost_dev *dev, uint8_t *config,
>>      msg.payload.config.offset = 0;
>>      msg.payload.config.size = config_len;
>>      if (vhost_user_write(dev, &msg, NULL, 0) < 0) {
>> +        error_setg_errno(errp, -EPROTO, "vhost_get_config failed");
>>          return -EPROTO;
>>      }
>>  
>>      if (vhost_user_read(dev, &msg) < 0) {
>> +        error_setg_errno(errp, -EPROTO, "vhost_get_config failed");
>>          return -EPROTO;
>>      }
>
> Oops, should be error_setg_errno(EPROTO)!

D'oh!  Thanks!