From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755979Ab1EDV4R (ORCPT ); Wed, 4 May 2011 17:56:17 -0400 Received: from e35.co.us.ibm.com ([32.97.110.153]:57542 "EHLO e35.co.us.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755634Ab1EDV4P (ORCPT ); Wed, 4 May 2011 17:56:15 -0400 From: Tom Lendacky Organization: IBM Linux Performance To: "Michael S. Tsirkin" Subject: Re: [PATCH 05/18] virtio: used event index interface Date: Wed, 4 May 2011 16:56:09 -0500 User-Agent: KMail/1.13.6 (Linux/2.6.35.12-90.fc14.i686.PAE; KDE/4.6.2; i686; ; ) Cc: linux-kernel@vger.kernel.org, Rusty Russell , 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 , steved@us.ibm.com, habanero@linux.vnet.ibm.com References: In-Reply-To: MIME-Version: 1.0 Content-Type: Text/Plain; charset="iso-8859-1" Content-Transfer-Encoding: 7bit Message-Id: <201105041656.11009.tahm@linux.vnet.ibm.com> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wednesday, May 04, 2011 03:51:09 PM Michael S. Tsirkin wrote: > Define a new feature bit for the guest to utilize a used_event index > (like Xen) instead if a flag bit to enable/disable interrupts. > > Signed-off-by: Michael S. Tsirkin > --- > include/linux/virtio_ring.h | 9 +++++++++ > 1 files changed, 9 insertions(+), 0 deletions(-) > > diff --git a/include/linux/virtio_ring.h b/include/linux/virtio_ring.h > index e4d144b..f5c1b75 100644 > --- a/include/linux/virtio_ring.h > +++ b/include/linux/virtio_ring.h > @@ -29,6 +29,10 @@ > /* We support indirect buffer descriptors */ > #define VIRTIO_RING_F_INDIRECT_DESC 28 > > +/* 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 > + > /* Virtio ring descriptors: 16 bytes. These can chain together via > "next". */ struct vring_desc { > /* Address (guest-physical). */ > @@ -83,6 +87,7 @@ struct vring { > * __u16 avail_flags; > * __u16 avail_idx; > * __u16 available[num]; > + * __u16 used_event_idx; > * > * // Padding to the next align boundary. > * char pad[]; > @@ -93,6 +98,10 @@ struct vring { > * struct vring_used_elem used[num]; > * }; > */ > +/* We publish the used event index at the end of the available ring. > + * It is at the end for backwards compatibility. */ > +#define vring_used_event(vr) ((vr)->avail->ring[(vr)->num]) > + > static inline void vring_init(struct vring *vr, unsigned int num, void *p, > unsigned long align) > { You should update the vring_size procedure to account for the extra field at the end of the available ring by change the "(2 + num)" to "(3 + num)": return ((sizeof(struct vring_desc) * num + sizeof(__u16) * (3 + num) Tom