Re: [Qemu-devel] [PATCH v3 13/28] vhost-user: check vhost_user_{read, write}() return value

[Michael S. Tsirkin]

On Wed, Jul 06, 2016 at 08:47:06PM +0200, address@hidden wrote:
> From: Marc-André Lureau <address@hidden>
> 
> More error checking to break code flow and report appropriate errors.
> 
> Signed-off-by: Marc-André Lureau <address@hidden>

So this will cause asserts here:

    /* inform backend of log switching, this must be done before
       releasing the current log, to ensure no logging is lost */
    r = dev->vhost_ops->vhost_set_log_base(dev, log_base, log);
    assert(r >= 0);

which is the opposite of what we want.

For vhost_net ioctl failure is a fatal error bit for
vhost user this means backend exited and will not change
memory so it's benign.

the right thing to do is to return 0 status to caller on most errors.

If that is necessary for debugging, add a printout for now.


> ---
>  hw/virtio/vhost-user.c | 50 
> ++++++++++++++++++++++++++++++++++----------------
>  1 file changed, 34 insertions(+), 16 deletions(-)
> 
> diff --git a/hw/virtio/vhost-user.c b/hw/virtio/vhost-user.c
> index 5dae496..819481d 100644
> --- a/hw/virtio/vhost-user.c
> +++ b/hw/virtio/vhost-user.c
> @@ -214,12 +214,14 @@ static int vhost_user_set_log_base(struct vhost_dev 
> *dev, uint64_t base,
>          fds[fd_num++] = log->fd;
>      }
>  
> -    vhost_user_write(dev, &msg, fds, fd_num);
> +    if (vhost_user_write(dev, &msg, fds, fd_num) < 0) {
> +        return -1;
> +    }
>  
>      if (shmfd) {
>          msg.size = 0;
>          if (vhost_user_read(dev, &msg) < 0) {
> -            return 0;
> +            return -1;
>          }
>  
>          if (msg.request != VHOST_USER_SET_LOG_BASE) {
> @@ -275,7 +277,9 @@ static int vhost_user_set_mem_table(struct vhost_dev *dev,
>      msg.size += sizeof(msg.payload.memory.padding);
>      msg.size += fd_num * sizeof(VhostUserMemoryRegion);
>  
> -    vhost_user_write(dev, &msg, fds, fd_num);
> +    if (vhost_user_write(dev, &msg, fds, fd_num) < 0) {
> +        return -1;
> +    }
>  
>      return 0;
>  }
> @@ -290,7 +294,9 @@ static int vhost_user_set_vring_addr(struct vhost_dev 
> *dev,
>          .size = sizeof(msg.payload.addr),
>      };
>  
> -    vhost_user_write(dev, &msg, NULL, 0);
> +    if (vhost_user_write(dev, &msg, NULL, 0) < 0) {
> +        return -1;
> +    }
>  
>      return 0;
>  }
> @@ -313,7 +319,9 @@ static int vhost_set_vring(struct vhost_dev *dev,
>          .size = sizeof(msg.payload.state),
>      };
>  
> -    vhost_user_write(dev, &msg, NULL, 0);
> +    if (vhost_user_write(dev, &msg, NULL, 0) < 0) {
> +        return -1;
> +    }
>  
>      return 0;
>  }
> @@ -360,10 +368,12 @@ static int vhost_user_get_vring_base(struct vhost_dev 
> *dev,
>          .size = sizeof(msg.payload.state),
>      };
>  
> -    vhost_user_write(dev, &msg, NULL, 0);
> +    if (vhost_user_write(dev, &msg, NULL, 0) < 0) {
> +        return -1;
> +    }
>  
>      if (vhost_user_read(dev, &msg) < 0) {
> -        return 0;
> +        return -1;
>      }
>  
>      if (msg.request != VHOST_USER_GET_VRING_BASE) {
> @@ -401,7 +411,9 @@ static int vhost_set_vring_file(struct vhost_dev *dev,
>          msg.payload.u64 |= VHOST_USER_VRING_NOFD_MASK;
>      }
>  
> -    vhost_user_write(dev, &msg, fds, fd_num);
> +    if (vhost_user_write(dev, &msg, fds, fd_num) < 0) {
> +        return -1;
> +    }
>  
>      return 0;
>  }
> @@ -427,7 +439,9 @@ static int vhost_user_set_u64(struct vhost_dev *dev, int 
> request, uint64_t u64)
>          .size = sizeof(msg.payload.u64),
>      };
>  
> -    vhost_user_write(dev, &msg, NULL, 0);
> +    if (vhost_user_write(dev, &msg, NULL, 0) < 0) {
> +        return -1;
> +    }
>  
>      return 0;
>  }
> @@ -455,10 +469,12 @@ static int vhost_user_get_u64(struct vhost_dev *dev, 
> int request, uint64_t *u64)
>          return 0;
>      }
>  
> -    vhost_user_write(dev, &msg, NULL, 0);
> +    if (vhost_user_write(dev, &msg, NULL, 0) < 0) {
> +        return -1;
> +    }
>  
>      if (vhost_user_read(dev, &msg) < 0) {
> -        return 0;
> +        return -1;
>      }
>  
>      if (msg.request != request) {
> @@ -489,7 +505,9 @@ static int vhost_user_set_owner(struct vhost_dev *dev)
>          .flags = VHOST_USER_VERSION,
>      };
>  
> -    vhost_user_write(dev, &msg, NULL, 0);
> +    if (vhost_user_write(dev, &msg, NULL, 0) < 0) {
> +        return -1;
> +    }
>  
>      return 0;
>  }
> @@ -501,7 +519,9 @@ static int vhost_user_reset_device(struct vhost_dev *dev)
>          .flags = VHOST_USER_VERSION,
>      };
>  
> -    vhost_user_write(dev, &msg, NULL, 0);
> +    if (vhost_user_write(dev, &msg, NULL, 0) < 0) {
> +        return -1;
> +    }
>  
>      return 0;
>  }
> @@ -588,7 +608,6 @@ static bool vhost_user_requires_shm_log(struct vhost_dev 
> *dev)
>  static int vhost_user_migration_done(struct vhost_dev *dev, char* mac_addr)
>  {
>      VhostUserMsg msg = { 0 };
> -    int err;
>  
>      assert(dev->vhost_ops->backend_type == VHOST_BACKEND_TYPE_USER);
>  
> @@ -605,8 +624,7 @@ static int vhost_user_migration_done(struct vhost_dev 
> *dev, char* mac_addr)
>          memcpy((char *)&msg.payload.u64, mac_addr, 6);
>          msg.size = sizeof(msg.payload.u64);
>  
> -        err = vhost_user_write(dev, &msg, NULL, 0);
> -        return err;
> +        return vhost_user_write(dev, &msg, NULL, 0);
>      }
>      return -1;
>  }
> -- 
> 2.9.0