From patchwork Sun Jan 10 14:21:07 2016 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: "Michael S. Tsirkin" X-Patchwork-Id: 7996511 Return-Path: X-Original-To: patchwork-xen-devel@patchwork.kernel.org Delivered-To: patchwork-parsemail@patchwork1.web.kernel.org Received: from mail.kernel.org (mail.kernel.org [198.145.29.136]) by patchwork1.web.kernel.org (Postfix) with ESMTP id 79A2E9F1CC for ; Sun, 10 Jan 2016 14:23:57 +0000 (UTC) Received: from mail.kernel.org (localhost [127.0.0.1]) by mail.kernel.org (Postfix) with ESMTP id 957412024D for ; Sun, 10 Jan 2016 14:23:56 +0000 (UTC) Received: from lists.xen.org (lists.xenproject.org [50.57.142.19]) (using TLSv1 with cipher AES256-SHA (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id A6B902025A for ; Sun, 10 Jan 2016 14:23:55 +0000 (UTC) Received: from localhost ([127.0.0.1] helo=lists.xen.org) by lists.xen.org with esmtp (Exim 4.72) (envelope-from ) id 1aIGrw-00027r-2l; Sun, 10 Jan 2016 14:21:20 +0000 Received: from mail6.bemta5.messagelabs.com ([195.245.231.135]) by lists.xen.org with esmtp (Exim 4.72) (envelope-from ) id 1aIGru-000267-GP for xen-devel@lists.xenproject.org; Sun, 10 Jan 2016 14:21:18 +0000 Received: from [85.158.139.211] by server-3.bemta-5.messagelabs.com id F8/DE-13487-DD862965; Sun, 10 Jan 2016 14:21:17 +0000 X-Env-Sender: mst@redhat.com X-Msg-Ref: server-9.tower-206.messagelabs.com!1452435675!14937185!1 X-Originating-IP: [209.132.183.28] X-SpamReason: No, hits=0.0 required=7.0 tests=sa_preprocessor: VHJ1c3RlZCBJUDogMjA5LjEzMi4xODMuMjggPT4gNTQwNjQ=\n X-StarScan-Received: X-StarScan-Version: 7.35.1; banners=-,-,- X-VirusChecked: Checked Received: (qmail 42430 invoked from network); 10 Jan 2016 14:21:16 -0000 Received: from mx1.redhat.com (HELO mx1.redhat.com) (209.132.183.28) by server-9.tower-206.messagelabs.com with DHE-RSA-AES256-GCM-SHA384 encrypted SMTP; 10 Jan 2016 14:21:16 -0000 Received: from int-mx10.intmail.prod.int.phx2.redhat.com (int-mx10.intmail.prod.int.phx2.redhat.com [10.5.11.23]) by mx1.redhat.com (Postfix) with ESMTPS id 56BC07D; Sun, 10 Jan 2016 14:21:15 +0000 (UTC) Received: from redhat.com (vpn1-5-155.ams2.redhat.com [10.36.5.155]) by int-mx10.intmail.prod.int.phx2.redhat.com (8.14.4/8.14.4) with SMTP id u0AEL8YI019556; Sun, 10 Jan 2016 09:21:08 -0500 Date: Sun, 10 Jan 2016 16:21:07 +0200 From: "Michael S. Tsirkin" To: linux-kernel@vger.kernel.org Message-ID: <1452426622-4471-34-git-send-email-mst@redhat.com> References: <1452426622-4471-1-git-send-email-mst@redhat.com> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <1452426622-4471-1-git-send-email-mst@redhat.com> X-Mutt-Fcc: =sent X-Scanned-By: MIMEDefang 2.68 on 10.5.11.23 Cc: linux-mips@linux-mips.org, linux-ia64@vger.kernel.org, linux-sh@vger.kernel.org, Peter Zijlstra , virtualization@lists.linux-foundation.org, "H. Peter Anvin" , sparclinux@vger.kernel.org, linux-arch@vger.kernel.org, linux-s390@vger.kernel.org, Russell King - ARM Linux , Arnd Bergmann , x86@kernel.org, xen-devel@lists.xenproject.org, Ingo Molnar , linux-xtensa@linux-xtensa.org, user-mode-linux-devel@lists.sourceforge.net, Stefano Stabellini , adi-buildroot-devel@lists.sourceforge.net, Thomas Gleixner , linux-metag@vger.kernel.org, linux-arm-kernel@lists.infradead.org, Andrew Cooper , Joe Perches , linuxppc-dev@lists.ozlabs.org, David Miller Subject: [Xen-devel] [PATCH v3 33/41] virtio_ring: use virt_store_mb X-BeenThere: xen-devel@lists.xen.org X-Mailman-Version: 2.1.13 Precedence: list List-Id: Xen developer discussion List-Unsubscribe: , List-Post: List-Help: List-Subscribe: , Sender: xen-devel-bounces@lists.xen.org Errors-To: xen-devel-bounces@lists.xen.org X-Spam-Status: No, score=-4.2 required=5.0 tests=BAYES_00, RCVD_IN_DNSWL_MED, UNPARSEABLE_RELAY autolearn=unavailable version=3.3.1 X-Spam-Checker-Version: SpamAssassin 3.3.1 (2010-03-16) on mail.kernel.org X-Virus-Scanned: ClamAV using ClamSMTP We need a full barrier after writing out event index, using virt_store_mb there seems better than open-coding. As usual, we need a wrapper to account for strong barriers. It's tempting to use this in vhost as well, for that, we'll need a variant of smp_store_mb that works on __user pointers. Signed-off-by: Michael S. Tsirkin --- include/linux/virtio_ring.h | 11 +++++++++++ drivers/virtio/virtio_ring.c | 15 +++++++++------ 2 files changed, 20 insertions(+), 6 deletions(-) diff --git a/include/linux/virtio_ring.h b/include/linux/virtio_ring.h index f3fa55b..a156e2b 100644 --- a/include/linux/virtio_ring.h +++ b/include/linux/virtio_ring.h @@ -45,6 +45,17 @@ static inline void virtio_wmb(bool weak_barriers) wmb(); } +static inline void virtio_store_mb(bool weak_barriers, + __virtio16 *p, __virtio16 v) +{ + if (weak_barriers) { + virt_store_mb(*p, v); + } else { + WRITE_ONCE(*p, v); + mb(); + } +} + struct virtio_device; struct virtqueue; diff --git a/drivers/virtio/virtio_ring.c b/drivers/virtio/virtio_ring.c index ee663c4..e12e385 100644 --- a/drivers/virtio/virtio_ring.c +++ b/drivers/virtio/virtio_ring.c @@ -517,10 +517,10 @@ void *virtqueue_get_buf(struct virtqueue *_vq, unsigned int *len) /* If we expect an interrupt for the next entry, tell host * by writing event index and flush out the write before * the read in the next get_buf call. */ - if (!(vq->avail_flags_shadow & VRING_AVAIL_F_NO_INTERRUPT)) { - vring_used_event(&vq->vring) = cpu_to_virtio16(_vq->vdev, vq->last_used_idx); - virtio_mb(vq->weak_barriers); - } + if (!(vq->avail_flags_shadow & VRING_AVAIL_F_NO_INTERRUPT)) + virtio_store_mb(vq->weak_barriers, + &vring_used_event(&vq->vring), + cpu_to_virtio16(_vq->vdev, vq->last_used_idx)); #ifdef DEBUG vq->last_add_time_valid = false; @@ -653,8 +653,11 @@ bool virtqueue_enable_cb_delayed(struct virtqueue *_vq) } /* TODO: tune this threshold */ bufs = (u16)(vq->avail_idx_shadow - vq->last_used_idx) * 3 / 4; - vring_used_event(&vq->vring) = cpu_to_virtio16(_vq->vdev, vq->last_used_idx + bufs); - virtio_mb(vq->weak_barriers); + + virtio_store_mb(vq->weak_barriers, + &vring_used_event(&vq->vring), + cpu_to_virtio16(_vq->vdev, vq->last_used_idx + bufs)); + if (unlikely((u16)(virtio16_to_cpu(_vq->vdev, vq->vring.used->idx) - vq->last_used_idx) > bufs)) { END_USE(vq); return false;