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=-9.0 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_PASS,URIBL_BLOCKED, USER_AGENT_GIT 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 DF7D0C282C0 for ; Wed, 23 Jan 2019 09:53:02 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id B7C9721726 for ; Wed, 23 Jan 2019 09:53:02 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727345AbfAWJxB (ORCPT ); Wed, 23 Jan 2019 04:53:01 -0500 Received: from mga07.intel.com ([134.134.136.100]:43150 "EHLO mga07.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727075AbfAWJxB (ORCPT ); Wed, 23 Jan 2019 04:53:01 -0500 X-Amp-Result: SKIPPED(no attachment in message) X-Amp-File-Uploaded: False Received: from orsmga002.jf.intel.com ([10.7.209.21]) by orsmga105.jf.intel.com with ESMTP/TLS/DHE-RSA-AES256-GCM-SHA384; 23 Jan 2019 01:53:00 -0800 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.56,510,1539673200"; d="scan'208";a="128190241" Received: from unknown (HELO dpdk-tbie.sh.intel.com) ([10.67.104.173]) by orsmga002.jf.intel.com with ESMTP; 23 Jan 2019 01:52:59 -0800 From: Tiwei Bie To: mst@redhat.com, jasowang@redhat.com, virtualization@lists.linux-foundation.org, linux-kernel@vger.kernel.org, virtio-dev@lists.oasis-open.org Subject: [PATCH v2] virtio: support VIRTIO_F_ORDER_PLATFORM Date: Wed, 23 Jan 2019 17:50:26 +0800 Message-Id: <20190123095026.8387-1-tiwei.bie@intel.com> X-Mailer: git-send-email 2.17.1 Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org This patch introduces the support for VIRTIO_F_ORDER_PLATFORM. If this feature is negotiated, the driver must use the barriers suitable for hardware devices. Otherwise, the device and driver are assumed to be implemented in software, that is they can be assumed to run on identical CPUs in an SMP configuration. Thus a weaker form of memory barriers is sufficient to yield better performance. It is recommended that an add-in card based PCI device offers this feature for portability. The device will fail to operate further or will operate in a slower emulation mode if this feature is offered but not accepted. Signed-off-by: Tiwei Bie --- v2: - Add more explanations in commit log (MST); 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? */ -- 2.17.1