Re: [Virtio-fs] [PATCH v2 01/25] DAX: vhost-user: Rework slave return values

[Greg Kurz <groug@kaod.org>]

On Wed, 14 Apr 2021 16:51:13 +0100
"Dr. David Alan Gilbert (git)" <dgilbert@redhat.com> 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>
> ---

LGTM

Just an indentation nit...

>  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;
>  
> @@ -429,5 +429,5 @@ int vhost_backend_handle_iotlb_msg(struct vhost_dev *dev,
>          break;
>      }
>  
> -    return ret;
> +    return !!ret;
>  }
> diff --git a/hw/virtio/vhost-user.c b/hw/virtio/vhost-user.c
> index ded0c10453..3e4a25e108 100644
> --- a/hw/virtio/vhost-user.c
> +++ b/hw/virtio/vhost-user.c
> @@ -1405,24 +1405,25 @@ static int vhost_user_reset_device(struct vhost_dev *dev)
>      return 0;
>  }
>  
> -static int vhost_user_slave_handle_config_change(struct vhost_dev *dev)
> +static uint64_t vhost_user_slave_handle_config_change(struct vhost_dev *dev)
>  {
>      int ret = -1;
>  
>      if (!dev->config_ops) {
> -        return -1;
> +        return true;
>      }
>  
>      if (dev->config_ops->vhost_dev_config_notifier) {
>          ret = dev->config_ops->vhost_dev_config_notifier(dev);
>      }
>  
> -    return ret;
> +    return !!ret;
>  }
>  
> -static int vhost_user_slave_handle_vring_host_notifier(struct vhost_dev *dev,
> -                                                       VhostUserVringArea *area,
> -                                                       int fd)
> +static uint64_t vhost_user_slave_handle_vring_host_notifier(
> +                struct vhost_dev *dev,
> +               VhostUserVringArea *area,
> +               int fd)

... here.

Anyway,

Reviewed-by: Greg Kurz <groug@kaod.org>

>  {
>      int queue_idx = area->u64 & VHOST_USER_VRING_IDX_MASK;
>      size_t page_size = qemu_real_host_page_size;
> @@ -1436,7 +1437,7 @@ static int vhost_user_slave_handle_vring_host_notifier(struct vhost_dev *dev,
>      if (!virtio_has_feature(dev->protocol_features,
>                              VHOST_USER_PROTOCOL_F_HOST_NOTIFIER) ||
>          vdev == NULL || queue_idx >= virtio_get_num_queues(vdev)) {
> -        return -1;
> +        return true;
>      }
>  
>      n = &user->notifier[queue_idx];
> @@ -1449,18 +1450,18 @@ static int vhost_user_slave_handle_vring_host_notifier(struct vhost_dev *dev,
>      }
>  
>      if (area->u64 & VHOST_USER_VRING_NOFD_MASK) {
> -        return 0;
> +        return false;
>      }
>  
>      /* Sanity check. */
>      if (area->size != page_size) {
> -        return -1;
> +        return true;
>      }
>  
>      addr = mmap(NULL, page_size, PROT_READ | PROT_WRITE, MAP_SHARED,
>                  fd, area->offset);
>      if (addr == MAP_FAILED) {
> -        return -1;
> +        return true;
>      }
>  
>      name = g_strdup_printf("vhost-user/host-notifier@%p mmaps[%d]",
> @@ -1471,13 +1472,13 @@ static int vhost_user_slave_handle_vring_host_notifier(struct vhost_dev *dev,
>  
>      if (virtio_queue_set_host_notifier_mr(vdev, queue_idx, &n->mr, true)) {
>          munmap(addr, page_size);
> -        return -1;
> +        return true;
>      }
>  
>      n->addr = addr;
>      n->set = true;
>  
> -    return 0;
> +    return false;
>  }
>  
>  static void close_slave_channel(struct vhost_user *u)
> @@ -1498,7 +1499,7 @@ static gboolean slave_read(QIOChannel *ioc, GIOCondition condition,
>      VhostUserPayload payload = { 0, };
>      Error *local_err = NULL;
>      gboolean rc = G_SOURCE_CONTINUE;
> -    int ret = 0;
> +    uint64_t ret = 0;
>      struct iovec iov;
>      g_autofree int *fd = NULL;
>      size_t fdsize = 0;
> @@ -1539,7 +1540,7 @@ static gboolean slave_read(QIOChannel *ioc, GIOCondition condition,
>          break;
>      default:
>          error_report("Received unexpected msg type: %d.", hdr.request);
> -        ret = -EINVAL;
> +        ret = true;
>      }
>  
>      /*
> @@ -1553,7 +1554,7 @@ static gboolean slave_read(QIOChannel *ioc, GIOCondition condition,
>          hdr.flags &= ~VHOST_USER_NEED_REPLY_MASK;
>          hdr.flags |= VHOST_USER_REPLY_MASK;
>  
> -        payload.u64 = !!ret;
> +        payload.u64 = ret;
>          hdr.size = sizeof(payload.u64);
>  
>          iovec[0].iov_base = &hdr;
> diff --git a/include/hw/virtio/vhost-backend.h b/include/hw/virtio/vhost-backend.h
> index 8a6f8e2a7a..64ac6b6444 100644
> --- a/include/hw/virtio/vhost-backend.h
> +++ b/include/hw/virtio/vhost-backend.h
> @@ -186,7 +186,7 @@ int vhost_backend_update_device_iotlb(struct vhost_dev *dev,
>  int vhost_backend_invalidate_device_iotlb(struct vhost_dev *dev,
>                                                   uint64_t iova, uint64_t len);
>  
> -int vhost_backend_handle_iotlb_msg(struct vhost_dev *dev,
> +uint64_t vhost_backend_handle_iotlb_msg(struct vhost_dev *dev,
>                                            struct vhost_iotlb_msg *imsg);
>  
>  int vhost_user_gpu_set_socket(struct vhost_dev *dev, int fd);