> -----Original Message----- > From: Chen, Junjie J > Sent: Thursday, March 15, 2018 12:24 AM > To: Tan, Jianfeng; maxime.coque...@redhat.com; y...@fridaylinux.org > Cc: dev@dpdk.org; Chen, Junjie J > Subject: [PATCH v4] doc: add driver limitation for vhost dequeue zero copy > > 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.c...@intel.com>
Reviewed-by: Jianfeng Tan <jianfeng....@intel.com> Thanks! > --- > 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
