From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752505Ab1EQGB3 (ORCPT ); Tue, 17 May 2011 02:01:29 -0400 Received: from mx1.redhat.com ([209.132.183.28]:6909 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752030Ab1EQGB1 (ORCPT ); Tue, 17 May 2011 02:01:27 -0400 Date: Tue, 17 May 2011 09:00:52 +0300 From: "Michael S. Tsirkin" To: Rusty Russell 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 Message-ID: <20110517060052.GB26989@redhat.com> References: <87aaewh5pg.fsf@rustcorp.com.au> <20110515124727.GA24932@redhat.com> <87k4drduzs.fsf@rustcorp.com.au> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <87k4drduzs.fsf@rustcorp.com.au> User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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? -- MST 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: Tue, 17 May 2011 09:00:52 +0300 Message-ID: <20110517060052.GB26989@redhat.com> References: <87aaewh5pg.fsf@rustcorp.com.au> <20110515124727.GA24932@redhat.com> <87k4drduzs.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: <87k4drduzs.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 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? -- MST