From patchwork Tue Feb 27 09:21:08 2018 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: junjie.j.chen@intel.com X-Patchwork-Id: 35434 X-Patchwork-Delegate: maxime.coquelin@redhat.com Return-Path: X-Original-To: patchwork@dpdk.org Delivered-To: patchwork@dpdk.org Received: from [92.243.14.124] (localhost [127.0.0.1]) by dpdk.org (Postfix) with ESMTP id C53101E20; Tue, 27 Feb 2018 02:42:44 +0100 (CET) Received: from mga02.intel.com (mga02.intel.com [134.134.136.20]) by dpdk.org (Postfix) with ESMTP id 022AFDE0 for ; Tue, 27 Feb 2018 02:42:42 +0100 (CET) X-Amp-Result: SKIPPED(no attachment in message) X-Amp-File-Uploaded: False Received: from fmsmga001.fm.intel.com ([10.253.24.23]) by orsmga101.jf.intel.com with ESMTP/TLS/DHE-RSA-AES256-GCM-SHA384; 26 Feb 2018 17:42:41 -0800 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.47,398,1515484800"; d="scan'208";a="33846183" Received: from dpdk-dev.sh.intel.com ([10.67.111.147]) by fmsmga001.fm.intel.com with ESMTP; 26 Feb 2018 17:42:40 -0800 From: Junjie Chen To: yliu@fridaylinux.org, maxime.coquelin@redhat.com, jianfeng.tan@intel.com Cc: dev@dpdk.org, Junjie Chen Date: Tue, 27 Feb 2018 04:21:08 -0500 Message-Id: <1519723268-28723-1-git-send-email-junjie.j.chen@intel.com> X-Mailer: git-send-email 2.0.1 In-Reply-To: <1519483453-12613-1-git-send-email-junjie.j.chen@intel.com> References: <1519483453-12613-1-git-send-email-junjie.j.chen@intel.com> Subject: [dpdk-dev] [PATCH v2] doc: add driver limitation for vhost dequeue zero copy X-BeenThere: dev@dpdk.org X-Mailman-Version: 2.1.15 Precedence: list List-Id: DPDK patches and discussions List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: dev-bounces@dpdk.org Sender: "dev" In vhost-switch example, when binding nic to vfio-pci, dequeue zero copy cannot work in VM2NIC mode due to no iommu dma mapping is setup for guest memory currently. Signed-off-by: Junjie Chen --- Changes in V2: - add doc in vhost lib doc/guides/prog_guide/vhost_lib.rst | 3 +++ doc/guides/sample_app_ug/vhost.rst | 5 ++++- 2 files changed, 7 insertions(+), 1 deletion(-) diff --git a/doc/guides/prog_guide/vhost_lib.rst b/doc/guides/prog_guide/vhost_lib.rst index 18227b6..bdf77d6 100644 --- a/doc/guides/prog_guide/vhost_lib.rst +++ b/doc/guides/prog_guide/vhost_lib.rst @@ -83,6 +83,9 @@ The following is an overview of some key Vhost API functions: of those segments, thus the fewer the segments, the quicker we will get the mapping. NOTE: we may speed it by using tree searching in future. + * zero copy does not work when using vfio-pci driver currently, this is + because we don't setup iommu dma mapping for guest memory. + - ``RTE_VHOST_USER_IOMMU_SUPPORT`` IOMMU support will be enabled when this flag is set. It is disabled by diff --git a/doc/guides/sample_app_ug/vhost.rst b/doc/guides/sample_app_ug/vhost.rst index a4bdc6a..840c1fd 100644 --- a/doc/guides/sample_app_ug/vhost.rst +++ b/doc/guides/sample_app_ug/vhost.rst @@ -147,7 +147,10 @@ retries on an RX burst, it takes effect only when rx retry is enabled. The default value is 15. **--dequeue-zero-copy** -Dequeue zero copy will be enabled when this option is given. +Dequeue zero copy will be enabled when this option is given, it is worth to +note that if NIC is binded to vfio-pci driver, dequeue zero copy cannot work +at VM2NIC mode (vm2vm=0) due to currently we don't setup iommu dma mapping for +guest memory. **--vlan-strip 0|1** VLAN strip option is removed, because different NICs have different behaviors