From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mga11.intel.com (mga11.intel.com [192.55.52.93]) by dpdk.org (Postfix) with ESMTP id CA05C325F for ; Mon, 12 Mar 2018 04:15:16 +0100 (CET) X-Amp-Result: SKIPPED(no attachment in message) X-Amp-File-Uploaded: False Received: from orsmga002.jf.intel.com ([10.7.209.21]) by fmsmga102.fm.intel.com with ESMTP/TLS/DHE-RSA-AES256-GCM-SHA384; 11 Mar 2018 20:15:15 -0700 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.47,459,1515484800"; d="scan'208";a="41115205" Received: from tanjianf-mobl.ccr.corp.intel.com (HELO [10.255.27.216]) ([10.255.27.216]) by orsmga002.jf.intel.com with ESMTP; 11 Mar 2018 20:15:12 -0700 To: Junjie Chen , yliu@fridaylinux.org, maxime.coquein@redhat.com References: <1519723268-28723-1-git-send-email-junjie.j.chen@intel.com> <1520590048-151284-1-git-send-email-junjie.j.chen@intel.com> Cc: dev@dpdk.org From: "Tan, Jianfeng" Message-ID: <3d82fe68-5f76-7f38-ffb7-08cc4021da53@intel.com> Date: Mon, 12 Mar 2018 11:15:11 +0800 User-Agent: Mozilla/5.0 (Windows NT 6.3; WOW64; rv:45.0) Gecko/20100101 Thunderbird/45.8.0 MIME-Version: 1.0 In-Reply-To: <1520590048-151284-1-git-send-email-junjie.j.chen@intel.com> Content-Type: text/plain; charset=windows-1252; format=flowed Content-Transfer-Encoding: 7bit Subject: Re: [dpdk-dev] [PATCH v3] 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: , X-List-Received-Date: Mon, 12 Mar 2018 03:15:17 -0000 On 3/9/2018 6:07 PM, Junjie Chen wrote: > In vhost-switch example, when binding nic to vfio-pci with iommu enabled, > 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 V3: > - update limitation to iommu > Changes in V2: > - add doc in vhost lib > > doc/guides/prog_guide/vhost_lib.rst | 5 +++++ > doc/guides/sample_app_ug/vhost.rst | 5 ++++- > 2 files changed, 9 insertions(+), 1 deletion(-) > > diff --git a/doc/guides/prog_guide/vhost_lib.rst b/doc/guides/prog_guide/vhost_lib.rst > index 18227b6..06d214f 100644 > --- a/doc/guides/prog_guide/vhost_lib.rst > +++ b/doc/guides/prog_guide/vhost_lib.rst > @@ -83,6 +83,11 @@ 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 driver with iommu mode currently, this Considering FreeBSD driver nic_uio does not support iommu, we can make "driver" more explicitly. For example, "driver with iommu mode" -> "vfio-pci with iommu mode" > + is because we don't setup iommu dma mapping for guest memory. > For example, when you bind device to vfio-pci driver, you need to set driver to work in noiommu mode. Reword the above sentence a little bit: "If vfio-pci is a must in your case, insert vfio-pci kernel module in noiommu mode." > + > - ``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..f0bb169 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 driver with iommu enabled, 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