From patchwork Wed Sep 7 15:20:48 2016 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Ladi Prosek X-Patchwork-Id: 9319505 Return-Path: Received: from mail.wl.linuxfoundation.org (pdx-wl-mail.web.codeaurora.org [172.30.200.125]) by pdx-korg-patchwork.web.codeaurora.org (Postfix) with ESMTP id C2CF260752 for ; Wed, 7 Sep 2016 15:21:34 +0000 (UTC) Received: from mail.wl.linuxfoundation.org (localhost [127.0.0.1]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id BD811293B7 for ; Wed, 7 Sep 2016 15:21:34 +0000 (UTC) Received: by mail.wl.linuxfoundation.org (Postfix, from userid 486) id B2581293D9; Wed, 7 Sep 2016 15:21:34 +0000 (UTC) X-Spam-Checker-Version: SpamAssassin 3.3.1 (2010-03-16) on pdx-wl-mail.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-6.9 required=2.0 tests=BAYES_00,RCVD_IN_DNSWL_HI autolearn=ham version=3.3.1 Received: from lists.gnu.org (lists.gnu.org [208.118.235.17]) (using TLSv1 with cipher AES256-SHA (256/256 bits)) (No client certificate requested) by mail.wl.linuxfoundation.org (Postfix) with ESMTPS id 42C6F293D9 for ; Wed, 7 Sep 2016 15:21:32 +0000 (UTC) Received: from localhost ([::1]:41522 helo=lists.gnu.org) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1bhefK-0000sZ-I7 for patchwork-qemu-devel@patchwork.kernel.org; Wed, 07 Sep 2016 11:21:30 -0400 Received: from eggs.gnu.org ([2001:4830:134:3::10]:44230) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1bheet-0000s4-BW for qemu-devel@nongnu.org; Wed, 07 Sep 2016 11:21:04 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1bheer-0003QI-0j for qemu-devel@nongnu.org; Wed, 07 Sep 2016 11:21:02 -0400 Received: from mx1.redhat.com ([209.132.183.28]:47412) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1bheeq-0003QE-R0 for qemu-devel@nongnu.org; Wed, 07 Sep 2016 11:21:00 -0400 Received: from int-mx09.intmail.prod.int.phx2.redhat.com (int-mx09.intmail.prod.int.phx2.redhat.com [10.5.11.22]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id 7CAD74E358; Wed, 7 Sep 2016 15:21:00 +0000 (UTC) Received: from dhcp-1-107.brq.redhat.com (dhcp-1-127.brq.redhat.com [10.34.1.127]) by int-mx09.intmail.prod.int.phx2.redhat.com (8.14.4/8.14.4) with ESMTP id u87FKt00003232; Wed, 7 Sep 2016 11:20:59 -0400 From: Ladi Prosek To: qemu-devel@nongnu.org Date: Wed, 7 Sep 2016 17:20:48 +0200 Message-Id: <1473261649-31465-3-git-send-email-lprosek@redhat.com> In-Reply-To: <1473261649-31465-1-git-send-email-lprosek@redhat.com> References: <1473261649-31465-1-git-send-email-lprosek@redhat.com> X-Scanned-By: MIMEDefang 2.68 on 10.5.11.22 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.38]); Wed, 07 Sep 2016 15:21:00 +0000 (UTC) X-detected-operating-system: by eggs.gnu.org: GNU/Linux 2.2.x-3.x [generic] X-Received-From: 209.132.183.28 Subject: [Qemu-devel] [PATCH 2/3] virtio: add virtqueue_rewind() X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.21 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: lprosek@redhat.com, rkagan@virtuozzo.com, stefanha@redhat.com, mst@redhat.com Errors-To: qemu-devel-bounces+patchwork-qemu-devel=patchwork.kernel.org@nongnu.org Sender: "Qemu-devel" X-Virus-Scanned: ClamAV using ClamSMTP From: Stefan Hajnoczi virtqueue_discard() requires a VirtQueueElement but virtio-balloon does not migrate its in-use element. Introduce a new function that is similar to virtqueue_discard() but doesn't require a VirtQueueElement. This will allow virtio-balloon to access element again after migration with the usual proviso that the guest may have modified the vring since last time. Cc: Michael S. Tsirkin Cc: Roman Kagan Cc: Stefan Hajnoczi Signed-off-by: Ladi Prosek Reviewed-by: Roman Kagan --- hw/virtio/virtio.c | 22 ++++++++++++++++++++++ include/hw/virtio/virtio.h | 1 + 2 files changed, 23 insertions(+) diff --git a/hw/virtio/virtio.c b/hw/virtio/virtio.c index 74c085c..3de6029 100644 --- a/hw/virtio/virtio.c +++ b/hw/virtio/virtio.c @@ -272,6 +272,28 @@ void virtqueue_discard(VirtQueue *vq, const VirtQueueElement *elem, virtqueue_unmap_sg(vq, elem, len); } +/* virtqueue_rewind: + * @vq: The #VirtQueue + * @num: Number of elements to push back + * + * Pretend that elements weren't popped from the virtqueue. The next + * virtqueue_pop() will refetch the oldest element. + * + * Use virtqueue_discard() instead if you have a VirtQueueElement. + * + * Returns: true on success, false if @num is greater than the number of in use + * elements. + */ +bool virtqueue_rewind(VirtQueue *vq, unsigned int num) +{ + if (num > vq->inuse) { + return false; + } + vq->last_avail_idx -= num; + vq->inuse -= num; + return true; +} + void virtqueue_fill(VirtQueue *vq, const VirtQueueElement *elem, unsigned int len, unsigned int idx) { diff --git a/include/hw/virtio/virtio.h b/include/hw/virtio/virtio.h index d2490c1..f05559d 100644 --- a/include/hw/virtio/virtio.h +++ b/include/hw/virtio/virtio.h @@ -154,6 +154,7 @@ void virtqueue_push(VirtQueue *vq, const VirtQueueElement *elem, void virtqueue_flush(VirtQueue *vq, unsigned int count); void virtqueue_discard(VirtQueue *vq, const VirtQueueElement *elem, unsigned int len); +bool virtqueue_rewind(VirtQueue *vq, unsigned int num); void virtqueue_fill(VirtQueue *vq, const VirtQueueElement *elem, unsigned int len, unsigned int idx);