Re: [PATCH v2] virtio: add VIRTIO_RING_NO_LEGACY

From: Michael S. Tsirkin
Date: Wed Sep 11 2019 - 05:29:59 EST


On Tue, Sep 10, 2019 at 05:53:44PM +0000, Matej Genci wrote:
> Add macro to disable legacy functions vring_init and vring_size.
>
> Signed-off-by: Matej Genci <matej.genci@xxxxxxxxxxx>
> ---
>
> V2: Put all legacy APIs inside guards.
>
> ---
> include/uapi/linux/virtio_ring.h | 8 ++++++++
> 1 file changed, 8 insertions(+)
>
> diff --git a/include/uapi/linux/virtio_ring.h b/include/uapi/linux/virtio_ring.h
> index 4c4e24c291a5..efe5a421b4ea 100644
> --- a/include/uapi/linux/virtio_ring.h
> +++ b/include/uapi/linux/virtio_ring.h
> @@ -118,6 +118,8 @@ struct vring_used {
> struct vring_used_elem ring[];
> };
>
> +#ifndef VIRTIO_RING_NO_LEGACY
> +
> struct vring {
> unsigned int num;
>
> @@ -128,6 +130,8 @@ struct vring {
> struct vring_used *used;
> };
>
> +#endif /* VIRTIO_RING_NO_LEGACY */
> +
> /* Alignment requirements for vring elements.
> * When using pre-virtio 1.0 layout, these fall out naturally.
> */
> @@ -135,6 +139,8 @@ struct vring {
> #define VRING_USED_ALIGN_SIZE 4
> #define VRING_DESC_ALIGN_SIZE 16
>
> +#ifndef VIRTIO_RING_NO_LEGACY
> +
> /* The standard layout for the ring is a continuous chunk of memory which looks
> * like this. We assume num is a power of 2.
> *
> @@ -195,6 +201,8 @@ static inline int vring_need_event(__u16 event_idx, __u16 new_idx, __u16 old)
> return (__u16)(new_idx - event_idx - 1) < (__u16)(new_idx - old);
> }
>
> +#endif /* VIRTIO_RING_NO_LEGACY */
> +
> struct vring_packed_desc_event {
> /* Descriptor Ring Change Event Offset/Wrap Counter. */
> __le16 off_wrap;

OK almost but vring_need_event is actually useful for all variants
so should be outside the guards :) Sorry about it.

--
MST