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    SubjectRe: [PATCH 06/18] virtio_ring: avail event index interface
    On Mon, May 09, 2011 at 01:43:15PM +0930, Rusty Russell wrote:
    > On Wed, 4 May 2011 23:51:19 +0300, "Michael S. Tsirkin" <mst@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@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.

    Hmm, it makes debugging easier as each side can disable
    publishing separately - I used it all the time when I saw
    e.g. networking stuck to guess whether I need to investigate the
    interrupt or the exit handling.

    But I'm not hung up on this.

    Let me know pls.

    --
    MST


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