[dpdk-dev] [PATCH 2/2] net: enable IOVA mode for PMDs

[Maxime Coquelin]

Hi Santosh

On 01/05/2018 01:10 PM, santosh wrote:
> Hi Maxim,
> 
> 
> On Friday 05 January 2018 04:02 PM, Maxime Coquelin wrote:
>> Hi Jianfeng,
>>
>> On 10/11/2017 12:33 PM, Jianfeng Tan wrote:
>>> If we want to enable IOVA mode, introduced by
>>> commit 93878cf0255e ("eal: introduce helper API for IOVA mode"),
>>> we need PMDs (for PCI devices) to expose this flag.
>>>
>>> Signed-off-by: Jianfeng Tan<jianfeng.tan at intel.com>
>>> ---
> 
> [...]
> 
>> Ferruh, I see you also faced problems with KNI, how did you solved it?
>>
> By checking lsmod for rte_kni module and if found then set .iova_mode = _pa, refer [1].
> You may follow similar approach.. meaning detect emulation mode Or if not then
> other-way to introduce --iova-mode=<> eal arg.

Thanks for the information

Detecting whether we are in host or guest is not that trivial, and as 
Peter pointed me out, the VT-d specifies the 39bits guest address width
so there are certainly some processors in the wild using it.

And I don't think introducing a new EAL arg in -stable is a good idea.
If this is the only solution, then we should keep PA by default.

When using intel IOMMU, I think the best solution is to forbid VA mode
if GAW is 39 bits.

Regards,
Maxime

> [1] http://dpdk.org/browse/dpdk/tree/lib/librte_eal/linuxapp/eal/eal.c#n810
> 
> Thanks.
> 
>> Thanks,
>> Maxime
>>
>> [0]: https://bugzilla.redhat.com/show_bug.cgi?id=1530957#c3
>