[Lguest] [PATCH 06/18] virtio_ring: avail event index interface
Rusty Russell
rusty at rustcorp.com.au
Mon May 9 14:13:15 EST 2011
On Wed, 4 May 2011 23:51:19 +0300, "Michael S. Tsirkin" <mst at redhat.com> wrote:
> Define a new feature bit for the host to
> declare that it uses an avail_event index
> (like Xen) instead of a feature bit
> to enable/disable interrupts.
>
> Signed-off-by: Michael S. Tsirkin <mst at redhat.com>
> ---
> include/linux/virtio_ring.h | 11 ++++++++---
> 1 files changed, 8 insertions(+), 3 deletions(-)
>
> diff --git a/include/linux/virtio_ring.h b/include/linux/virtio_ring.h
> index f5c1b75..f791772 100644
> --- a/include/linux/virtio_ring.h
> +++ b/include/linux/virtio_ring.h
> @@ -32,6 +32,9 @@
> /* The Guest publishes the used index for which it expects an interrupt
> * at the end of the avail ring. Host should ignore the avail->flags field. */
> #define VIRTIO_RING_F_USED_EVENT_IDX 29
> +/* The Host publishes the avail index for which it expects a kick
> + * at the end of the used ring. Guest should ignore the used->flags field. */
> +#define VIRTIO_RING_F_AVAIL_EVENT_IDX 32
Are you really sure we want to separate the two? Seems a little simpler
to have one bit to mean "we're publishing our threshold". For someone
implementing this from scratch, it's a little simpler.
Or are there cases where the old style makes more sense?
Thanks,
Rusty.
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