Re: [RFC PATCH for 8.1 2/6] vdpa: add vhost_vdpa_reset_status_fd

[Stefano Garzarella]

On Fri, Mar 17, 2023 at 03:55:38PM +0100, Eugenio Pérez wrote:
> This allows to reset a vhost-vdpa device from external subsystems like
> vhost-net.  It is used in subsequent patches to negotiate features and
> probe for CVQ ASID isolation.
>
> Signed-off-by: Eugenio Pérez <eperezma@redhat.com>
> ---
> include/hw/virtio/vhost-vdpa.h |  1 +
> hw/virtio/vhost-vdpa.c         | 58 +++++++++++++++++++++++-----------
> 2 files changed, 41 insertions(+), 18 deletions(-)
>
> diff --git a/include/hw/virtio/vhost-vdpa.h b/include/hw/virtio/vhost-vdpa.h
> index c278a2a8de..28de7da91e 100644
> --- a/include/hw/virtio/vhost-vdpa.h
> +++ b/include/hw/virtio/vhost-vdpa.h
> @@ -54,6 +54,7 @@ typedef struct vhost_vdpa {
>     VhostVDPAHostNotifier notifier[VIRTIO_QUEUE_MAX];
> } VhostVDPA;
>
> +void vhost_vdpa_reset_status_fd(int fd);
> int vhost_vdpa_get_iova_range(int fd, struct vhost_vdpa_iova_range *iova_range);
>
> int vhost_vdpa_dma_map(struct vhost_vdpa *v, uint32_t asid, hwaddr iova,
> diff --git a/hw/virtio/vhost-vdpa.c b/hw/virtio/vhost-vdpa.c
> index bbabea18f3..7a2053b8d9 100644
> --- a/hw/virtio/vhost-vdpa.c
> +++ b/hw/virtio/vhost-vdpa.c
> @@ -335,38 +335,45 @@ static const MemoryListener vhost_vdpa_memory_listener = {
>     .region_del = vhost_vdpa_listener_region_del,
> };
>
> -static int vhost_vdpa_call(struct vhost_dev *dev, unsigned long int request,
> -                             void *arg)
> +static int vhost_vdpa_dev_fd(const struct vhost_dev *dev)

What is the purpose of this refactoring?
I guess, since vhost_net does not have `struct vhost_dev *` we want to
use fd directly?

It might be better to split this patch into two.

> {
>     struct vhost_vdpa *v = dev->opaque;
> -    int fd = v->device_fd;
> -    int ret;
>
>     assert(dev->vhost_ops->backend_type == VHOST_BACKEND_TYPE_VDPA);
> +    return v->device_fd;
> +}
> +
> +static int vhost_vdpa_call_fd(int fd, unsigned long int request, void *arg)
> +{
> +    int ret = ioctl(fd, request, arg);
>
> -    ret = ioctl(fd, request, arg);
>     return ret < 0 ? -errno : ret;
> }
>
> -static int vhost_vdpa_add_status(struct vhost_dev *dev, uint8_t status)
> +static int vhost_vdpa_call(struct vhost_dev *dev, unsigned long int request,
> +                           void *arg)
> +{
> +    return vhost_vdpa_call_fd(vhost_vdpa_dev_fd(dev), request, arg);
> +}
> +
> +static int vhost_vdpa_add_status_fd(int fd, uint8_t status)
> {
>     uint8_t s;
>     int ret;
>
> -    trace_vhost_vdpa_add_status(dev, status);
> -    ret = vhost_vdpa_call(dev, VHOST_VDPA_GET_STATUS, &s);
> +    ret = vhost_vdpa_call_fd(fd, VHOST_VDPA_GET_STATUS, &s);
>     if (ret < 0) {
>         return ret;
>     }
>
>     s |= status;
>
> -    ret = vhost_vdpa_call(dev, VHOST_VDPA_SET_STATUS, &s);
> +    ret = vhost_vdpa_call_fd(fd, VHOST_VDPA_SET_STATUS, &s);
>     if (ret < 0) {
>         return ret;
>     }
>
> -    ret = vhost_vdpa_call(dev, VHOST_VDPA_GET_STATUS, &s);
> +    ret = vhost_vdpa_call_fd(fd, VHOST_VDPA_GET_STATUS, &s);
>     if (ret < 0) {
>         return ret;
>     }
> @@ -378,6 +385,12 @@ static int vhost_vdpa_add_status(struct vhost_dev *dev, 
> uint8_t status)
>     return 0;
> }
>
> +static int vhost_vdpa_add_status(struct vhost_dev *dev, uint8_t status)
> +{
> +    trace_vhost_vdpa_add_status(dev, status);
> +    return vhost_vdpa_add_status_fd(vhost_vdpa_dev_fd(dev), status);
> +}
> +
> int vhost_vdpa_get_iova_range(int fd, struct vhost_vdpa_iova_range *iova_range)
> {
>     int ret = ioctl(fd, VHOST_VDPA_GET_IOVA_RANGE, iova_range);
> @@ -709,16 +722,20 @@ static int vhost_vdpa_get_device_id(struct vhost_dev *dev,
>     return ret;
> }
>
> +static int vhost_vdpa_reset_device_fd(int fd)
> +{
> +    uint8_t status = 0;
> +
> +    return vhost_vdpa_call_fd(fd, VHOST_VDPA_SET_STATUS, &status);
> +}
> +
> static int vhost_vdpa_reset_device(struct vhost_dev *dev)
> {
>     struct vhost_vdpa *v = dev->opaque;
> -    int ret;
> -    uint8_t status = 0;
>
> -    ret = vhost_vdpa_call(dev, VHOST_VDPA_SET_STATUS, &status);
> -    trace_vhost_vdpa_reset_device(dev);
>     v->suspended = false;

I think it is pre-existing, but if VHOST_VDPA_SET_STATUS fails,
should we set anyway `v->suspended = false`?

Thanks,
Stefano