From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:43110) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1Xix2c-0002H0-Dd for qemu-devel@nongnu.org; Mon, 27 Oct 2014 23:01:55 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1Xix2X-0000Ub-Bc for qemu-devel@nongnu.org; Mon, 27 Oct 2014 23:01:50 -0400 Received: from szxga02-in.huawei.com ([119.145.14.65]:55175) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1Xix2W-0000TR-Na for qemu-devel@nongnu.org; Mon, 27 Oct 2014 23:01:45 -0400 From: Bin Wu Date: Tue, 28 Oct 2014 02:13:02 +0000 Message-ID: <1414462382-24264-1-git-send-email-wu.wubin@huawei.com> MIME-Version: 1.0 Content-Type: text/plain Subject: [Qemu-devel] [PATCH] hw/virtio/virtio.c: fix the vring_avail_event error List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: qemu-devel@nongnu.org Cc: pbonzini@redhat.com, famz@redhat.com, Bin Wu , mst@redhat.com The event idx in virtio is an effective way to reduce the number of interrupts and exits of the guest. When the guest puts an request into the virtio ring, it doesn't exit immediately to inform the backend. Instead, the guest checks the "avail" event idx to determine the notification. In virtqueue_pop, when a request is poped, the current avail event idx should be set to the number of vq->last_avail_idx. Signed-off-by: Bin Wu --- hw/virtio/virtio.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/hw/virtio/virtio.c b/hw/virtio/virtio.c index 2c236bf..013979a 100644 --- a/hw/virtio/virtio.c +++ b/hw/virtio/virtio.c @@ -469,7 +469,7 @@ int virtqueue_pop(VirtQueue *vq, VirtQueueElement *elem) i = head = virtqueue_get_head(vq, vq->last_avail_idx++); if (vdev->guest_features & (1 << VIRTIO_RING_F_EVENT_IDX)) { - vring_avail_event(vq, vring_avail_idx(vq)); + vring_avail_event(vq, vq->last_avail_idx); } if (vring_desc_flags(vdev, desc_pa, i) & VRING_DESC_F_INDIRECT) { -- 1.7.12.4