Re: [PATCH v3 03/26] DAX: vhost-user: Rework slave return values

[Stefan Hajnoczi <stefanha@redhat.com>]

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On Wed, Apr 28, 2021 at 12:00:37PM +0100, Dr. David Alan Gilbert (git) wrote:
> From: "Dr. David Alan Gilbert" <dgilbert@redhat.com>
> 
> All the current slave handlers on the qemu side generate an 'int'
> return value that's squashed down to a bool (!!ret) and stuffed into
> a uint64_t (field of a union) to be returned.
> 
> Move the uint64_t type back up through the individual handlers so
> that we can make one actually return a full uint64_t.
> 
> Note that the definition in the interop spec says most of these
> cases are defined as returning 0 on success and non-0 for failure,
> so it's OK to change from a bool to another non-0.
> 
> Vivek:
> This is needed because upcoming patches in series will add new functions
> which want to return full error code. Existing functions continue to
> return true/false so, it should not lead to change of behavior for
> existing users.
> 
> Signed-off-by: Dr. David Alan Gilbert <dgilbert@redhat.com>
> Reviewed-by: Greg Kurz <groug@kaod.org>
> ---
>  hw/virtio/vhost-backend.c         |  6 +++---
>  hw/virtio/vhost-user.c            | 31 ++++++++++++++++---------------
>  include/hw/virtio/vhost-backend.h |  2 +-
>  3 files changed, 20 insertions(+), 19 deletions(-)
> 
> diff --git a/hw/virtio/vhost-backend.c b/hw/virtio/vhost-backend.c
> index 31b33bde37..1686c94767 100644
> --- a/hw/virtio/vhost-backend.c
> +++ b/hw/virtio/vhost-backend.c
> @@ -401,8 +401,8 @@ int vhost_backend_invalidate_device_iotlb(struct vhost_dev *dev,
>      return -ENODEV;
>  }
>  
> -int vhost_backend_handle_iotlb_msg(struct vhost_dev *dev,
> -                                          struct vhost_iotlb_msg *imsg)
> +uint64_t vhost_backend_handle_iotlb_msg(struct vhost_dev *dev,
> +                                        struct vhost_iotlb_msg *imsg)
>  {
>      int ret = 0;

This patch is messy. We want uint64_t but these functions use int ret
internally. The actual return values are true/false instead of int 0 and
1.

Please use uint64_t everywhere: return 0 for success and 1 for failure
instead of bool literals and change the type of the local ret variables
to uint64_t.

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