From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752836Ab1EQCt2 (ORCPT ); Mon, 16 May 2011 22:49:28 -0400 Received: from ozlabs.org ([203.10.76.45]:56601 "EHLO ozlabs.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752206Ab1EQCt0 (ORCPT ); Mon, 16 May 2011 22:49:26 -0400 From: Rusty Russell To: "Michael S. Tsirkin" Cc: linux-kernel@vger.kernel.org, Carsten Otte , Christian Borntraeger , linux390@de.ibm.com, Martin Schwidefsky , Heiko Carstens , Shirley Ma , lguest@lists.ozlabs.org, virtualization@lists.linux-foundation.org, netdev@vger.kernel.org, linux-s390@vger.kernel.org, kvm@vger.kernel.org, Krishna Kumar , Tom Lendacky , steved@us.ibm.com, habanero@linux.vnet.ibm.com Subject: Re: [PATCH 06/18] virtio_ring: avail event index interface In-Reply-To: <20110515124727.GA24932@redhat.com> References: <87aaewh5pg.fsf@rustcorp.com.au> <20110515124727.GA24932@redhat.com> User-Agent: Notmuch/0.5 (http://notmuchmail.org) Emacs/23.2.1 (i686-pc-linux-gnu) Date: Mon, 16 May 2011 15:53:19 +0930 Message-ID: <87k4drduzs.fsf@rustcorp.com.au> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@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. 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, 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.