From mboxrd@z Thu Jan 1 00:00:00 1970 From: "Michael S. Tsirkin" Subject: Re: [PATCH 06/18] virtio_ring: avail event index interface Date: Sun, 15 May 2011 15:47:27 +0300 Message-ID: <20110515124727.GA24932@redhat.com> References: <87aaewh5pg.fsf@rustcorp.com.au> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Cc: Krishna Kumar , Carsten Otte , lguest-uLR06cmDAlY/bJ5BZ2RsiQ@public.gmane.org, Shirley Ma , kvm-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, linux-s390-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, netdev-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, habanero-23VcF4HTsmIX0ybBhKVfKdBPR1lH4CV8@public.gmane.org, Heiko Carstens , linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, virtualization-cunTk1MwBs9QetFLy7KEm3xJsTq8ys+cHZ5vskTnxNA@public.gmane.org, steved-r/Jw6+rmf7HQT0dZR+AlfA@public.gmane.org, Christian Borntraeger , Tom Lendacky , Martin Schwidefsky , linux390-tA70FqPdS9bQT0dZR+AlfA@public.gmane.org To: Rusty Russell Return-path: Content-Disposition: inline In-Reply-To: <87aaewh5pg.fsf-8n+1lVoiYb80n/F98K4Iww@public.gmane.org> List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: lguest-bounces+glkvl-lguest=m.gmane.org-uLR06cmDAlY/bJ5BZ2RsiQ@public.gmane.org Sender: lguest-bounces+glkvl-lguest=m.gmane.org-uLR06cmDAlY/bJ5BZ2RsiQ@public.gmane.org List-Id: netdev.vger.kernel.org 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" 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 > > --- > > 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