From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752436Ab1EIFx5 (ORCPT ); Mon, 9 May 2011 01:53:57 -0400 Received: from ozlabs.org ([203.10.76.45]:40426 "EHLO ozlabs.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752067Ab1EIFxz (ORCPT ); Mon, 9 May 2011 01:53:55 -0400 From: Rusty Russell To: "Michael S. Tsirkin" , linux-kernel@vger.kernel.org Cc: Carsten Otte , Christian Borntraeger , linux390@de.ibm.com, Martin Schwidefsky , Heiko Carstens , Shirley Ma , lguest@lists.ozlabs.org, linux-kernel@vger.kernel.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: References: User-Agent: Notmuch/0.3.1 (http://notmuchmail.org) Emacs/23.1.1 (i686-pc-linux-gnu) Date: Mon, 09 May 2011 13:43:15 +0930 Message-ID: <87aaewh5pg.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 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. 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@rustcorp.com.au> References: Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Return-path: In-Reply-To: Sender: linux-kernel-owner@vger.kernel.org List-Archive: List-Post: To: "Michael S. Tsirkin" Cc: Carsten Otte , Christian Borntraeger , linux390@de.ibm.com, Martin Schwidefsky , Heiko Carstens , Shirley Ma , lguest@lists.ozlabs.org, linux-kernel@vger.kernel.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 List-ID: 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.