[dpdk-dev] [PATCH v10 3/9] linuxapp/eal_pci: get iommu class

santosh santosh.shukla at caviumnetworks.com
Wed Oct 11 06:43:44 CEST 2017

On Wednesday 11 October 2017 07:17 AM, Tan, Jianfeng wrote:
> Hi,
> Nice patch series. But I still have a small question about below flag.
> On 10/6/2017 7:03 PM, Santosh Shukla wrote:
>> Get iommu class of PCI device on the bus and returns preferred iova
>> mapping mode for that bus.
>> Patch also introduces RTE_PCI_DRV_IOVA_AS_VA drv flag.
>> Flag used when driver needs to operate in iova=va mode.
> Does this flag indicate a must to use VA as IOVA, or a nice-to-have one? In detail, above commit log says, "needs to operate in iova=va mode", but the comment in the patch indicates this flag means "driver supports IOVA as VA".
> If it's the latter case, I would suppose all drivers support to use VA as IOVA, if the NICs are binded to vfio-pci (iommu mode). Please correct me if I'm wrong.
- Any iommu backed pmd could choose to use this flag.
- Reasoning for need was performance for our external mempool pmd: avoid phy2virt translation on
mbuf thus save cycles.

> Thanks,
> Jianfeng

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