From mboxrd@z Thu Jan 1 00:00:00 1970 From: Rusty Russell Subject: Re: [PATCH 06/18] virtio_ring: avail event index interface Date: Mon, 09 May 2011 13:43:15 +0930 Message-ID: <87aaewh5pg.fsf__35597.0399141826$1304920508$gmane$org@rustcorp.com.au> References: Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: virtualization-bounces@lists.linux-foundation.org Errors-To: virtualization-bounces@lists.linux-foundation.org To: "Michael S. Tsirkin" Cc: Krishna Kumar , Carsten Otte , lguest@lists.ozlabs.org, Shirley Ma , kvm@vger.kernel.org, linux-s390@vger.kernel.org, netdev@vger.kernel.org, habanero@linux.vnet.ibm.com, Heiko Carstens , linux-kernel@vger.kernel.org, virtualization@lists.linux-foundation.org, steved@us.ibm.com, Christian Borntraeger , Tom Lendacky , Martin Schwidefsky , linux390@de.ibm.com List-Id: virtualization@lists.linuxfoundation.org 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.