From: "Tan, Jianfeng" <jianfeng.tan@intel.com>
To: Junjie Chen <junjie.j.chen@intel.com>,
yliu@fridaylinux.org, maxime.coquein@redhat.com
Cc: dev@dpdk.org
Subject: Re: [dpdk-dev] [PATCH v3] doc: add driver limitation for vhost dequeue zero copy
Date: Mon, 12 Mar 2018 11:15:11 +0800 [thread overview]
Message-ID: <3d82fe68-5f76-7f38-ffb7-08cc4021da53@intel.com> (raw)
In-Reply-To: <1520590048-151284-1-git-send-email-junjie.j.chen@intel.com>
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 <junjie.j.chen@intel.com>
> ---
> 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
next prev parent reply other threads:[~2018-03-12 3:15 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 [this message]
2018-03-13 9:19 ` Chen, Junjie J
2018-03-14 16:24 ` [dpdk-dev] [PATCH v4] " Junjie Chen
2018-03-19 6:56 ` Tan, Jianfeng
2018-03-29 12:14 ` Maxime Coquelin
2018-04-11 14:34 ` Maxime Coquelin
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