From patchwork Fri Aug 12 15:32:57 2016 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Stefan Hajnoczi X-Patchwork-Id: 9277319 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 3709E600CB for ; Fri, 12 Aug 2016 15:58:12 +0000 (UTC) Received: from mail.wl.linuxfoundation.org (localhost [127.0.0.1]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id 286DF28A72 for ; Fri, 12 Aug 2016 15:58:12 +0000 (UTC) Received: by mail.wl.linuxfoundation.org (Postfix, from userid 486) id 1BCC428A84; Fri, 12 Aug 2016 15:58:12 +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 BED9B28A72 for ; Fri, 12 Aug 2016 15:58:11 +0000 (UTC) Received: from localhost ([::1]:53159 helo=lists.gnu.org) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1bYEqY-0006UW-TM for patchwork-qemu-devel@patchwork.kernel.org; Fri, 12 Aug 2016 11:58:10 -0400 Received: from eggs.gnu.org ([2001:4830:134:3::10]:45474) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1bYESM-00018Z-2O for qemu-devel@nongnu.org; Fri, 12 Aug 2016 11:33:18 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1bYESK-0006Sk-0B for qemu-devel@nongnu.org; Fri, 12 Aug 2016 11:33:09 -0400 Received: from mx1.redhat.com ([209.132.183.28]:44548) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1bYESJ-0006Sf-Qg for qemu-devel@nongnu.org; Fri, 12 Aug 2016 11:33:07 -0400 Received: from int-mx13.intmail.prod.int.phx2.redhat.com (int-mx13.intmail.prod.int.phx2.redhat.com [10.5.11.26]) (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 6C95580F7D; Fri, 12 Aug 2016 15:33:07 +0000 (UTC) Received: from localhost (ovpn-112-61.ams2.redhat.com [10.36.112.61]) by int-mx13.intmail.prod.int.phx2.redhat.com (8.14.4/8.14.4) with ESMTP id u7CFX6wA003671; Fri, 12 Aug 2016 11:33:06 -0400 From: Stefan Hajnoczi To: qemu-devel@nongnu.org Date: Fri, 12 Aug 2016 16:32:57 +0100 Message-Id: <1471015978-1123-4-git-send-email-stefanha@redhat.com> In-Reply-To: <1471015978-1123-1-git-send-email-stefanha@redhat.com> References: <1471015978-1123-1-git-send-email-stefanha@redhat.com> X-Scanned-By: MIMEDefang 2.68 on 10.5.11.26 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.27]); Fri, 12 Aug 2016 15:33:07 +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 for-2.7 3/4] 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: gaudenz@debian.org, "Michael S. Tsirkin" , Stefan Hajnoczi , Luiz Capitulino Errors-To: qemu-devel-bounces+patchwork-qemu-devel=patchwork.kernel.org@nongnu.org Sender: "Qemu-devel" X-Virus-Scanned: ClamAV using ClamSMTP 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. Signed-off-by: Stefan Hajnoczi --- 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 00158b6..22727ba 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);