From patchwork Sun May 29 08:11:29 2016 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: "Wang, Wei W" X-Patchwork-Id: 9139631 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 C781260759 for ; Sun, 29 May 2016 00:16:11 +0000 (UTC) Received: from mail.wl.linuxfoundation.org (localhost [127.0.0.1]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id 9DA1E27C3B for ; Sun, 29 May 2016 00:16:11 +0000 (UTC) Received: by mail.wl.linuxfoundation.org (Postfix, from userid 486) id 90DC32807E; Sun, 29 May 2016 00:16:11 +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=-5.0 required=2.0 tests=BAYES_00, DATE_IN_FUTURE_06_12, RCVD_IN_DNSWL_HI autolearn=unavailable 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 44DC727C3B for ; Sun, 29 May 2016 00:16:11 +0000 (UTC) Received: from localhost ([::1]:54495 helo=lists.gnu.org) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1b6oOo-00041s-9Y for patchwork-qemu-devel@patchwork.kernel.org; Sat, 28 May 2016 20:16:10 -0400 Received: from eggs.gnu.org ([2001:4830:134:3::10]:33378) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1b6oOF-000404-NI for qemu-devel@nongnu.org; Sat, 28 May 2016 20:15:36 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1b6oOA-0006kc-3a for qemu-devel@nongnu.org; Sat, 28 May 2016 20:15:34 -0400 Received: from mga01.intel.com ([192.55.52.88]:6080) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1b6oO9-0006kP-Ks for qemu-devel@nongnu.org; Sat, 28 May 2016 20:15:30 -0400 Received: from fmsmga002.fm.intel.com ([10.253.24.26]) by fmsmga101.fm.intel.com with ESMTP; 28 May 2016 17:15:28 -0700 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.26,381,1459839600"; d="scan'208";a="990754609" Received: from unknown (HELO otc18.sh.intel.com.com) ([10.239.48.138]) by fmsmga002.fm.intel.com with ESMTP; 28 May 2016 17:15:26 -0700 From: Wei Wang To: kvm@vger.kernel.org, qemu-devel@nongnu.org, virtio-comment@lists.oasis-open.org, mst@redhat.com, stefanha@redhat.com, pbonzini@redhat.com Date: Sun, 29 May 2016 16:11:29 +0800 Message-Id: <1464509494-159509-2-git-send-email-wei.w.wang@intel.com> X-Mailer: git-send-email 1.8.3.1 In-Reply-To: <1464509494-159509-1-git-send-email-wei.w.wang@intel.com> References: <1464509494-159509-1-git-send-email-wei.w.wang@intel.com> X-detected-operating-system: by eggs.gnu.org: Genre and OS details not recognized. X-Received-From: 192.55.52.88 Subject: [Qemu-devel] [PATCH 1/6 Resend] Vhost-pci RFC: Introduction 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: Wei Wang Errors-To: qemu-devel-bounces+patchwork-qemu-devel=patchwork.kernel.org@nongnu.org Sender: "Qemu-devel" X-Virus-Scanned: ClamAV using ClamSMTP Signed-off-by: Wei Wang --- Introduction | 31 +++++++++++++++++++++++++++++++ 1 file changed, 31 insertions(+) create mode 100644 Introduction diff --git a/Introduction b/Introduction new file mode 100644 index 0000000..8774676 --- /dev/null +++ b/Introduction @@ -0,0 +1,31 @@ +Current vhost-user based backend designs for virtio-net devices present scaling +challenges, as communication intensive applications (e.g. virtual network +functions) running in VMs start to stress this centralized design and resources +assigned to it. + +Vhost-pci was initially proposed by Michael S. Tsirkin with vIOMMU support to +offer a protected and point-to-point based inter-VM communication. In many +cases, such as network function virtualization (NFV) and software defined +networking (SDN) usages, VMs in an isolated network trust each other and they +may be chained together to complete a task. In these use cases, people care +more about performance than security. In this RFC we present a comprehensive +design of vhost-pci without vIOMMU support. A VM with such a vhost-pci device +is able to copy data to another VM's memory directly. The advantages of using +vhost-pci over vhost-user are: 1) one less packet copy per packet transfer; and +2) better scalability. + +To follow the naming conventions in the virtio specification, we call the VM +who sends packets to the destination VM the device VM, and the VM who provides +the vring and receives packets the driver VM. The vhost-pci device/driver works +independently in the device VM. It can be considered as a simple device mapping +the entire memory of a driver VM. But a lot of times, it may be used to +communicate to a virtio device in the driver VM. That is, it usually plays the +role of a backend part of a virtio device of a driver VM. + +The vhost-pci design is not limited to networking usages. The design presented +in this RFC is quite fundamental, and it is potentially useful for other +inter-VM data moving usages. For the convenience of descriptions, we will +simply use "virtio device" to refer to the device on a driver VM that is backed +by a vhost-pci device. The figures of this RFC are shown in this link: +https://etherpad.opnfv.org/p/vhost-pci_RFC +