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

[Tan, Jianfeng]

> -----Original Message-----
> From: santosh [mailto:santosh.shukla at caviumnetworks.com]
> Sent: Wednesday, October 11, 2017 1:38 PM
> To: Tan, Jianfeng; olivier.matz at 6wind.com; dev at dpdk.org
> Cc: thomas at monjalon.net; jerin.jacob at caviumnetworks.com;
> hemant.agrawal at nxp.com; aconole at redhat.com;
> stephen at networkplumber.org; Burakov, Anatoly; gaetan.rivet at 6wind.com;
> shreyansh.jain at nxp.com; Richardson, Bruce; Gonzalez Monroy, Sergio;
> maxime.coquelin at redhat.com
> Subject: Re: [dpdk-dev] [PATCH v10 3/9] linuxapp/eal_pci: get iommu class
> 
> 
> On Wednesday 11 October 2017 11:01 AM, Tan, Jianfeng wrote:
> >
> >
> > 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.
> >
> to hint bus layer about iova=va mapping choice for _this_ driver and default
> is iova=pa.
> 

So that sounds if this flag is set by some PMD, we must use iova=va.

Then how about we enable this, iova=va, if only all PCI devices are binded to vfio-pci (iommu mode)?

Thanks,
Jianfeng