From: Rusty Russell Subject: Re: [PATCH 06/18] virtio_ring: avail event index interface Date: Mon, 16 May 2011 15:53:19 +0930 Message-ID: <87k4drduzs.fsf@rustcorp.com.au> References: <87aaewh5pg.fsf@rustcorp.com.au> <20110515124727.GA24932@redhat.com> 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: "Michael S. Tsirkin" Return-path: In-Reply-To: <20110515124727.GA24932-H+wXaHxf7aLQT0dZR+AlfA@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: kvm.vger.kernel.org On Sun, 15 May 2011 15:47:27 +0300, "Michael S. Tsirkin" wrote: > 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 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. If we combine them into one, then these patches no longer depend on the feature bit expansion, which is worthwhile (though I'll take both). Thanks, Rusty.