From patchwork Wed May 26 19:50:42 2010 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: "Michael S. Tsirkin" X-Patchwork-Id: 102487 Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by demeter.kernel.org (8.14.3/8.14.3) with ESMTP id o4QJuF3O012439 for ; Wed, 26 May 2010 19:56:16 GMT Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757407Ab0EZTzd (ORCPT ); Wed, 26 May 2010 15:55:33 -0400 Received: from mx1.redhat.com ([209.132.183.28]:29053 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1757028Ab0EZTzc (ORCPT ); Wed, 26 May 2010 15:55:32 -0400 Received: from int-mx01.intmail.prod.int.phx2.redhat.com (int-mx01.intmail.prod.int.phx2.redhat.com [10.5.11.11]) by mx1.redhat.com (8.13.8/8.13.8) with ESMTP id o4QJsvlZ030696 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-SHA bits=256 verify=OK); Wed, 26 May 2010 15:54:57 -0400 Received: from redhat.com (vpn-6-108.tlv.redhat.com [10.35.6.108]) by int-mx01.intmail.prod.int.phx2.redhat.com (8.13.8/8.13.8) with SMTP id o4QJssdk023173; Wed, 26 May 2010 15:54:55 -0400 Date: Wed, 26 May 2010 22:50:42 +0300 From: "Michael S. Tsirkin" To: Rusty Russell , linux-kernel@vger.kernel.org, virtualization@lists.linux-foundation.org, kvm@vger.kernel.org, qemu-devel@nongnu.org Subject: [PATCHv2-RFC 2/2] virtio: publish used idx Message-ID: <0a3c79049e834e6550c880dea83becb401f25bdd.1274903330.git.mst@redhat.com> References: MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: X-Mutt-Fcc: =sent User-Agent: Mutt/1.5.19 (2009-01-05) X-Scanned-By: MIMEDefang 2.67 on 10.5.11.11 Sender: kvm-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: kvm@vger.kernel.org X-Greylist: IP, sender and recipient auto-whitelisted, not delayed by milter-greylist-4.2.3 (demeter.kernel.org [140.211.167.41]); Wed, 26 May 2010 19:56:16 +0000 (UTC) diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c index 78eb319..30e7483 100644 --- a/drivers/net/virtio_net.c +++ b/drivers/net/virtio_net.c @@ -23,6 +23,7 @@ #include #include #include +#include #include #include #include @@ -1056,6 +1057,7 @@ static unsigned int features[] = { VIRTIO_NET_F_GUEST_ECN, VIRTIO_NET_F_GUEST_UFO, VIRTIO_NET_F_MRG_RXBUF, VIRTIO_NET_F_STATUS, VIRTIO_NET_F_CTRL_VQ, VIRTIO_NET_F_CTRL_RX, VIRTIO_NET_F_CTRL_VLAN, + VIRTIO_RING_F_PUBLISH_USED, }; static struct virtio_driver virtio_net_driver = { diff --git a/drivers/virtio/virtio_ring.c b/drivers/virtio/virtio_ring.c index 2241342..4a5458e 100644 --- a/drivers/virtio/virtio_ring.c +++ b/drivers/virtio/virtio_ring.c @@ -92,6 +92,9 @@ struct vring_virtqueue /* Last used index we've seen. */ u16 last_used_idx; + /* Publish last used index we've seen at this location. */ + u16 *publish_last_used_idx; + /* How to notify other side. FIXME: commonalize hcalls! */ void (*notify)(struct virtqueue *vq); @@ -325,7 +328,7 @@ void *virtqueue_get_buf(struct virtqueue *_vq, unsigned int *len) /* detach_buf clears data, so grab it now. */ ret = vq->data[i]; detach_buf(vq, i); - vq->last_used_idx++; + *vq->publish_last_used_idx = ++vq->last_used_idx; END_USE(vq); return ret; } @@ -348,6 +351,8 @@ bool virtqueue_enable_cb(struct virtqueue *_vq) /* We optimistically turn back on interrupts, then check if there was * more to do. */ vq->vring.avail->flags &= ~VRING_AVAIL_F_NO_INTERRUPT; + /* Besides flags write, this barrier also flushes out + * last available index write. */ virtio_mb(); if (unlikely(more_used(vq))) { END_USE(vq); @@ -425,13 +430,19 @@ struct virtqueue *vring_new_virtqueue(unsigned int num, if (!vq) return NULL; - vring_init(&vq->vring, num, pages, vring_align, false); + vring_init(&vq->vring, num, pages, vring_align, + virtio_has_feature(vdev, VIRTIO_RING_F_PUBLISH_USED)); + if (virtio_has_feature(vdev, VIRTIO_RING_F_PUBLISH_USED)) + vq->publish_last_used_idx = &vq->vring.avail->last_used_idx; + else + vq->publish_last_used_idx = &vq->last_used_idx; vq->vq.callback = callback; vq->vq.vdev = vdev; vq->vq.name = name; vq->notify = notify; vq->broken = false; vq->last_used_idx = 0; + *vq->publish_last_used_idx = 0; vq->num_added = 0; list_add_tail(&vq->vq.list, &vdev->vqs); #ifdef DEBUG @@ -473,6 +484,8 @@ void vring_transport_features(struct virtio_device *vdev) switch (i) { case VIRTIO_RING_F_INDIRECT_DESC: break; + case VIRTIO_RING_F_PUBLISH_USED: + break; default: /* We don't understand this bit. */ clear_bit(i, vdev->features); diff --git a/include/linux/virtio_ring.h b/include/linux/virtio_ring.h index c5f3ee7..0de35c5 100644 --- a/include/linux/virtio_ring.h +++ b/include/linux/virtio_ring.h @@ -29,6 +29,9 @@ /* We support indirect buffer descriptors */ #define VIRTIO_RING_F_INDIRECT_DESC 28 +/* The Guest publishes last-seen used index at the end of the avail ring. */ +#define VIRTIO_RING_F_PUBLISH_USED 29 + /* Virtio ring descriptors: 16 bytes. These can chain together via "next". */ struct vring_desc { /* Address (guest-physical). */ @@ -50,6 +53,7 @@ struct vring_avail { struct vring_avail_ctrl { __u16 flags; __u16 idx; + __u16 last_used_idx; }; /* u32 is used here for ids for padding reasons. */