From: Junjie Chen <junjie.j.chen@intel.com>
To: jianfeng.tan@intel.com, maxime.coquelin@redhat.com, yliu@fridaylinux.org
Cc: dev@dpdk.org, Junjie Chen <junjie.j.chen@intel.com>
Subject: [dpdk-dev] [PATCH v4] doc: add driver limitation for vhost dequeue zero copy
Date: Wed, 14 Mar 2018 12:24:16 -0400 [thread overview]
Message-ID: <1521044656-105962-1-git-send-email-junjie.j.chen@intel.com> (raw)
In-Reply-To: <1520590048-151284-1-git-send-email-junjie.j.chen@intel.com>
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 <junjie.j.chen@intel.com>
---
Changes in V4:
- make words more accurate
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..b49e36e 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 can not work when using vfio-pci with iommu mode currently, this
+ is because we don't setup iommu dma mapping for guest memory. If you have
+ to use vfio-pci driver, please 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
--
2.0.1
next prev parent reply other threads:[~2018-03-14 8:45 UTC|newest]
Thread overview: 14+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-02-24 14:44 [dpdk-dev] [PATCH] " Junjie Chen
2018-02-26 4:44 ` Tan, Jianfeng
2018-03-13 9:12 ` Kovacevic, Marko
2018-03-13 9:18 ` Chen, Junjie J
2018-02-27 9:21 ` [dpdk-dev] [PATCH v2] " Junjie Chen
2018-03-06 8:57 ` Maxime Coquelin
2018-03-09 5:17 ` Chen, Junjie J
2018-03-09 10:07 ` [dpdk-dev] [PATCH v3] " Junjie Chen
2018-03-12 3:15 ` Tan, Jianfeng
2018-03-13 9:19 ` Chen, Junjie J
2018-03-14 16:24 ` Junjie Chen [this message]
2018-03-19 6:56 ` [dpdk-dev] [PATCH v4] " Tan, Jianfeng
2018-03-29 12:14 ` Maxime Coquelin
2018-04-11 14:34 ` Maxime Coquelin
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