From mboxrd@z Thu Jan 1 00:00:00 1970 From: Junjie Chen Subject: [PATCH v3] doc: add driver limitation for vhost dequeue zero copy Date: Fri, 9 Mar 2018 05:07:28 -0500 Message-ID: <1520590048-151284-1-git-send-email-junjie.j.chen@intel.com> References: <1519723268-28723-1-git-send-email-junjie.j.chen@intel.com> Cc: dev@dpdk.org, Junjie Chen To: yliu@fridaylinux.org, maxime.coquein@redhat.com, jianfeng.tan@intel.com Return-path: Received: from mga01.intel.com (mga01.intel.com [192.55.52.88]) by dpdk.org (Postfix) with ESMTP id 6BA8B5F21 for ; Fri, 9 Mar 2018 03:29:10 +0100 (CET) In-Reply-To: <1519723268-28723-1-git-send-email-junjie.j.chen@intel.com> 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 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 + 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. + - ``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 -- 2.0.1