Re: [dpdk-dev] [PATCH] eal: force IOVA mode to physical

[santosh <santosh.shukla@caviumnetworks.com>]

On Thursday 30 August 2018 05:43 PM, Hemant wrote:
> External Email
>
> Hi,
>
> On 8/30/2018 3:13 PM, Gaëtan Rivet wrote:
>> Hi,
>>
>> On Thu, Aug 30, 2018 at 10:09:04AM +0100, Burakov, Anatoly wrote:
>>> On 29-Aug-18 4:58 PM, eric zhang wrote:
>>>> This patch adds a configuration option to force the IOVA mode to
>>>> physical address (PA). There exists virtual devices that are not
>>>> directly attached to the PCI bus, and therefore the auto detection
>>>> of the IOVA mode based on probing the PCI bus and IOMMU configuration
>>>> may not report the required addressing mode. Having the configuration
>>>> option permits the mode to be explicitly configured in this scenario.
>>>>
>>>> Signed-off-by: eric zhang <eric.zhang@windriver.com>
>>>> ---
>>> Defining this at compile-time seems like an overkill. Wouldn't it be better
>>> to just add an EAL command-line option to force IOVA mode to a particular
>>> value?
> That is a good suggestion.
>>> -- 
>>> Thanks,
>>> Anatoly
>> What is the bus of these devices and why not implement get_iommu_class
>> in it?
> There are cases, where you are using dpdk libraries with external
> libraries and you need to change the default behavior DPDK lib to use
> physical address instead of virtual address.
> Providing an option to user will help.
>
>
More appropriate solution could be:
* Either fix it at bus layer .. i.e.. get_iommu_class()..
* Or introduce something like [1] --iova-mode=<pa/va> param.

Former is better solution than latter if autodetection is a key criteria.
Thanks.

[1] http://patchwork.dpdk.org/patch/25192/