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: Wed, 18 May 2011 09:38:24 +0930 Message-ID: <87wrhona4n.fsf__36237.3423100964$1305680174$gmane$org@rustcorp.com.au> References: <87aaewh5pg.fsf@rustcorp.com.au> <20110515124727.GA24932@redhat.com> <87k4drduzs.fsf@rustcorp.com.au> <20110517060052.GB26989@redhat.com> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <20110517060052.GB26989@redhat.com> 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 Tue, 17 May 2011 09:00:52 +0300, "Michael S. Tsirkin" wrote: > On Mon, May 16, 2011 at 03:53:19PM +0930, Rusty Russell wrote: > > 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. > > Yes, I know. But if we do expand feature bits anyway, for debugging > and profiling if nothing else it's useful to have them separate ... > If you take both why does the order matter? Damage control. Then if something breaks, it doesn't break everything. Cheers, Rusty.