On 10/11/2017 12:43 PM, santosh wrote:
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.
But if this is characterized by assumption for all PMDs, why do we
trouble to introduce this flag.
- Reasoning for need was performance for our external mempool pmd: avoid
phy2virt translation on
mbuf thus save cycles.
Agreed, and it's also for running DPDK without root privilege.
Thanks,
Jianfeng
