[dpdk-dev] [PATCH v3 01/11] eal/pci: introduce PCI driver iova as va flag

[santosh]

Hi Maxime,

On Tuesday 11 July 2017 02:39 PM, Maxime Coquelin wrote:

>
>
> On 07/11/2017 08:16 AM, Santosh Shukla wrote:
>> Introducing RTE_PCI_DRV_NEED_IOVA_VA flag. Flag used when driver needs
>> to operate in iova=va mode.
>>
>> Why driver need iova=va mapping?
>>
>> On NPU style co-processors like Octeontx, the buffer recycling has been
>> done in HW, unlike SW model. Here is the data flow:
>> 1) On control path, Fill the HW mempool with buffers(iova as pa address)
>> 2) on rx_burst, HW gives you IOVA address(iova as pa address)
>> 3) As application expects VA to operate on it, rx_burst() needs to
>> convert to _va from _pa. Which is very expensive.
>> Instead of that if iova as va mapping, we can avoid the cost of
>> converting with help of IOMMU/SMMU.
>>
>> Signed-off-by: Santosh Shukla<santosh.shukla at caviumnetworks.com>
>> Signed-off-by: Jerin Jacob<jerin.jacob at caviumnetworks.com>
>> ---
>>   lib/librte_eal/common/include/rte_pci.h | 2 ++
>>   1 file changed, 2 insertions(+)
>>
>> diff --git a/lib/librte_eal/common/include/rte_pci.h b/lib/librte_eal/common/include/rte_pci.h
>> index 8b123391c..ac79040dd 100644
>> --- a/lib/librte_eal/common/include/rte_pci.h
>> +++ b/lib/librte_eal/common/include/rte_pci.h
>> @@ -202,6 +202,8 @@ struct rte_pci_bus {
>>   #define RTE_PCI_DRV_INTR_RMV 0x0010
>>   /** Device driver needs to keep mapped resources if unsupported dev detected */
>>   #define RTE_PCI_DRV_KEEP_MAPPED_RES 0x0020
>> +/** Device driver needs iova as va */
>> +#define RTE_PCI_DRV_NEED_IOVA_VA 0X0040
>>   
>
> Maybe not a big deal, but using NEED tends to say that the driver cannot
> work if not using VA as IOVA. If my understanding is correct, this is
> not the case, the performance will be poor but the device will be
> functional.
>
Agree, How about renaming to RTE_PCI_DRV_IOVA_AS_VA, make sense?

Thanks.

> Maxime