From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-7.0 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_PASS,URIBL_BLOCKED autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id D7C4DC282C3 for ; Wed, 23 Jan 2019 03:08:48 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id A7A4020811 for ; Wed, 23 Jan 2019 03:08:48 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726979AbfAWDIM (ORCPT ); Tue, 22 Jan 2019 22:08:12 -0500 Received: from mx1.redhat.com ([209.132.183.28]:34274 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726843AbfAWDIM (ORCPT ); Tue, 22 Jan 2019 22:08:12 -0500 Received: from smtp.corp.redhat.com (int-mx02.intmail.prod.int.phx2.redhat.com [10.5.11.12]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id 10A2699D29; Wed, 23 Jan 2019 03:08:12 +0000 (UTC) Received: from [10.72.12.174] (ovpn-12-174.pek2.redhat.com [10.72.12.174]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 6BD5D60C67; Wed, 23 Jan 2019 03:08:07 +0000 (UTC) Subject: Re: [virtio-dev] [PATCH] virtio: support VIRTIO_F_ORDER_PLATFORM To: Tiwei Bie , mst@redhat.com, virtualization@lists.linux-foundation.org, linux-kernel@vger.kernel.org, virtio-dev@lists.oasis-open.org References: <20190122170346.6279-1-tiwei.bie@intel.com> From: Jason Wang Message-ID: Date: Wed, 23 Jan 2019 11:08:04 +0800 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.2.1 MIME-Version: 1.0 In-Reply-To: <20190122170346.6279-1-tiwei.bie@intel.com> Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 8bit Content-Language: en-US X-Scanned-By: MIMEDefang 2.79 on 10.5.11.12 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.38]); Wed, 23 Jan 2019 03:08:12 +0000 (UTC) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 2019/1/23 上午1:03, Tiwei Bie wrote: > This patch introduces the support for VIRTIO_F_ORDER_PLATFORM. > When this feature is negotiated, driver will use the barriers > suitable for hardware devices. > > Signed-off-by: Tiwei Bie > --- > drivers/virtio/virtio_ring.c | 8 ++++++++ > include/uapi/linux/virtio_config.h | 6 ++++++ > 2 files changed, 14 insertions(+) > > diff --git a/drivers/virtio/virtio_ring.c b/drivers/virtio/virtio_ring.c > index cd7e755484e3..27d3f057493e 100644 > --- a/drivers/virtio/virtio_ring.c > +++ b/drivers/virtio/virtio_ring.c > @@ -1609,6 +1609,9 @@ static struct virtqueue *vring_create_virtqueue_packed( > !context; > vq->event = virtio_has_feature(vdev, VIRTIO_RING_F_EVENT_IDX); > > + if (virtio_has_feature(vdev, VIRTIO_F_ORDER_PLATFORM)) > + vq->weak_barriers = false; > + > vq->packed.ring_dma_addr = ring_dma_addr; > vq->packed.driver_event_dma_addr = driver_event_dma_addr; > vq->packed.device_event_dma_addr = device_event_dma_addr; > @@ -2079,6 +2082,9 @@ struct virtqueue *__vring_new_virtqueue(unsigned int index, > !context; > vq->event = virtio_has_feature(vdev, VIRTIO_RING_F_EVENT_IDX); > > + if (virtio_has_feature(vdev, VIRTIO_F_ORDER_PLATFORM)) > + vq->weak_barriers = false; > + > vq->split.queue_dma_addr = 0; > vq->split.queue_size_in_bytes = 0; > > @@ -2213,6 +2219,8 @@ void vring_transport_features(struct virtio_device *vdev) > break; > case VIRTIO_F_RING_PACKED: > break; > + case VIRTIO_F_ORDER_PLATFORM: > + break; > default: > /* We don't understand this bit. */ > __virtio_clear_bit(vdev, i); > diff --git a/include/uapi/linux/virtio_config.h b/include/uapi/linux/virtio_config.h > index 1196e1c1d4f6..ff8e7dc9d4dd 100644 > --- a/include/uapi/linux/virtio_config.h > +++ b/include/uapi/linux/virtio_config.h > @@ -78,6 +78,12 @@ > /* This feature indicates support for the packed virtqueue layout. */ > #define VIRTIO_F_RING_PACKED 34 > > +/* > + * This feature indicates that memory accesses by the driver and the > + * device are ordered in a way described by the platform. > + */ > +#define VIRTIO_F_ORDER_PLATFORM 36 > + > /* > * Does the device support Single Root I/O Virtualization? > */ I wonder whether or not this is sufficient. Is dma barrier implies a mmio barrier? Looks not. See ia64/include/asm/barrier.h:  * Note: "mb()" and its variants cannot be used as a fence to order  * accesses to memory mapped I/O registers.  For that, mf.a needs to  * be used.  However, we don't want to always use mf.a because (a)  * it's (presumably) much slower than mf and (b) mf.a is supported for  * sequential memory pages only.  */ #define mb()            ia64_mf() #define rmb()           mb() #define wmb()           mb() #define dma_rmb()       mb() =>efine dma_wmb()       mb() Thanks