From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:39478) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1XkE0w-0007mS-Rx for qemu-devel@nongnu.org; Fri, 31 Oct 2014 11:22:10 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1Xk0Pj-00060d-PI for qemu-devel@nongnu.org; Thu, 30 Oct 2014 20:50:08 -0400 Received: from szxga03-in.huawei.com ([119.145.14.66]:20753) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1Xk0Pj-0005ID-5F for qemu-devel@nongnu.org; Thu, 30 Oct 2014 20:50:03 -0400 Message-ID: <5452DC9F.803@huawei.com> Date: Fri, 31 Oct 2014 08:49:35 +0800 From: Bin Wu MIME-Version: 1.0 References: <1414462382-24264-1-git-send-email-wu.wubin@huawei.com> <20141030164803.GB32387@stefanha-thinkpad.redhat.com> In-Reply-To: <20141030164803.GB32387@stefanha-thinkpad.redhat.com> Content-Type: text/plain; charset="ISO-8859-1" Content-Transfer-Encoding: 7bit Subject: Re: [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: Stefan Hajnoczi Cc: pbonzini@redhat.com, famz@redhat.com, qemu-devel@nongnu.org, mst@redhat.com On 2014/10/31 0:48, Stefan Hajnoczi wrote: > On Tue, Oct 28, 2014 at 02:13:02AM +0000, Bin Wu wrote: >> 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); >> } > > hw/virtio/dataplane/vring.c: > > if (vdev->guest_features & (1 << VIRTIO_RING_F_EVENT_IDX)) { > vring_avail_event(&vring->vr) = vring->vr.avail->idx; > } > > This is equivalent to the virtio.c code you are replacing, so it should > be updated too. > > Stefan > Thanks, stefan. I'll send another patch later. -- Bin Wu