From patchwork Fri Aug 30 07:59:32 2013 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Cornelia Huck X-Patchwork-Id: 271167 Return-Path: X-Original-To: incoming@patchwork.ozlabs.org Delivered-To: patchwork-incoming@bilbo.ozlabs.org Received: from lists.gnu.org (lists.gnu.org [IPv6:2001:4830:134:3::11]) (using TLSv1 with cipher AES256-SHA (256/256 bits)) (Client did not present a certificate) by ozlabs.org (Postfix) with ESMTPS id 01F102C0096 for ; Fri, 30 Aug 2013 18:00:29 +1000 (EST) Received: from localhost ([::1]:47911 helo=lists.gnu.org) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1VFJd5-0000tu-8e for incoming@patchwork.ozlabs.org; Fri, 30 Aug 2013 04:00:27 -0400 Received: from eggs.gnu.org ([2001:4830:134:3::10]:59596) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1VFJcY-0000qK-Kd for qemu-devel@nongnu.org; Fri, 30 Aug 2013 04:00:03 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1VFJcN-0008O2-8M for qemu-devel@nongnu.org; Fri, 30 Aug 2013 03:59:54 -0400 Received: from e06smtp12.uk.ibm.com ([195.75.94.108]:47232) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1VFJcM-0008Ns-V6 for qemu-devel@nongnu.org; Fri, 30 Aug 2013 03:59:43 -0400 Received: from /spool/local by e06smtp12.uk.ibm.com with IBM ESMTP SMTP Gateway: Authorized Use Only! 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Violators will be prosecuted; Fri, 30 Aug 2013 08:53:13 +0100 Received: from b06cxnps3074.portsmouth.uk.ibm.com (d06relay09.portsmouth.uk.ibm.com [9.149.109.194]) by d06dlp02.portsmouth.uk.ibm.com (Postfix) with ESMTP id 76B442190059 for ; Fri, 30 Aug 2013 08:59:38 +0100 (BST) Received: from d06av11.portsmouth.uk.ibm.com (d06av11.portsmouth.uk.ibm.com [9.149.37.252]) by b06cxnps3074.portsmouth.uk.ibm.com (8.13.8/8.13.8/NCO v10.0) with ESMTP id r7U7xQbh63307846 for ; Fri, 30 Aug 2013 07:59:26 GMT Received: from d06av11.portsmouth.uk.ibm.com (localhost [127.0.0.1]) by d06av11.portsmouth.uk.ibm.com (8.14.4/8.14.4/NCO v10.0 AVout) with ESMTP id r7U7xb6Q006388 for ; Fri, 30 Aug 2013 01:59:38 -0600 Received: from tuxmaker.boeblingen.de.ibm.com (tuxmaker.boeblingen.de.ibm.com [9.152.85.9]) by d06av11.portsmouth.uk.ibm.com (8.14.4/8.14.4/NCO v10.0 AVin) with ESMTP id r7U7xah3006349; Fri, 30 Aug 2013 01:59:37 -0600 From: Cornelia Huck To: Alexander Graf Date: Fri, 30 Aug 2013 09:59:32 +0200 Message-Id: <1377849572-42883-2-git-send-email-cornelia.huck@de.ibm.com> X-Mailer: git-send-email 1.8.3.4 In-Reply-To: <1377849572-42883-1-git-send-email-cornelia.huck@de.ibm.com> References: <1377849572-42883-1-git-send-email-cornelia.huck@de.ibm.com> X-TM-AS-MML: No X-Content-Scanned: Fidelis XPS MAILER x-cbid: 13083007-8372-0000-0000-00000707E63A X-detected-operating-system: by eggs.gnu.org: GNU/Linux 2.4.x-2.6.x [generic] X-Received-From: 195.75.94.108 Cc: Cornelia Huck , Christian Borntraeger , qemu-devel , Dominik Dingel Subject: [Qemu-devel] [PATCH] s390-ccw.img: Fix waiting for virtio processing. X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.14 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: qemu-devel-bounces+incoming=patchwork.ozlabs.org@nongnu.org Sender: qemu-devel-bounces+incoming=patchwork.ozlabs.org@nongnu.org The guest side must not manipulate the index for the used buffers. Instead, remember the state of the used buffer locally and wait until it has moved. Signed-off-by: Cornelia Huck --- pc-bios/s390-ccw/virtio.c | 10 +++++++--- pc-bios/s390-ccw/virtio.h | 1 + 2 files changed, 8 insertions(+), 3 deletions(-) diff --git a/pc-bios/s390-ccw/virtio.c b/pc-bios/s390-ccw/virtio.c index 49f2d29..03f6fde 100644 --- a/pc-bios/s390-ccw/virtio.c +++ b/pc-bios/s390-ccw/virtio.c @@ -150,8 +150,6 @@ static void vring_send_buf(struct vring *vr, void *p, int len, int flags) if (!(flags & VRING_DESC_F_NEXT)) { vr->avail->idx++; } - - vr->used->idx = vr->next_idx; } static u64 get_clock(void) @@ -180,7 +178,13 @@ static int vring_wait_reply(struct vring *vr, int timeout) struct subchannel_id schid = vr->schid; int r = 0; - while (vr->used->idx == vr->next_idx) { + vr->used_idx = vr->used->idx; + /* + * Wait until the used index has moved. + * Note: This is only race-free if the host doesn't start draining + * the queue out of its own accord. + */ + while (vr->used->idx == vr->used_idx) { vring_notify(schid); if (timeout && (get_second() >= target_second)) { r = 1; diff --git a/pc-bios/s390-ccw/virtio.h b/pc-bios/s390-ccw/virtio.h index 86fdd57..772a63f 100644 --- a/pc-bios/s390-ccw/virtio.h +++ b/pc-bios/s390-ccw/virtio.h @@ -115,6 +115,7 @@ struct vring_used { struct vring { unsigned int num; int next_idx; + int used_idx; struct vring_desc *desc; struct vring_avail *avail; struct vring_used *used;