Re: [dpdk-dev] Hotplug support for VFIO

[Alejandro Lucero <alejandro.lucero@netronome.com>]

I just wanted to clarify the hotplug VFIO is not the problem, as I can see
it, but the unplug. When attaching a device the current VFIO code will be
used, but there is no code for doing the IOMMU unmapping when unplugging.

On Wed, Feb 8, 2017 at 3:43 PM, Alejandro Lucero <
alejandro.lucero@netronome.com> wrote:

> Hi Eelco,
>
> On Wed, Feb 8, 2017 at 9:41 AM, Eelco Chaudron <echaudron@redhat.com>
> wrote:
>
>> Hi Anatoly,
>>
>> This will be great... If you want I can do some testing on (early)
>> patches if required.
>>
>> Also do you know why it is currently not supported, i.e. what are the
>> limitations?
>>
>> Thanks,
>>
>
> I assume your reply was to my previous email and not to Anatoly's one. My
> apologies if this assumption is wrong.
> By the way, you did not reply to the list, but I'm doing to do so because
> this could be interesting to other people. Also, I'm CCing hotplug UIO
> developer, Tetsuya Mukawa, since there is no a specific maintainer for this
> functionality.
>
> I think the main problem for supporting VFIO hotplug is to deal with what
> VFIO does, this is IOMMU mappings.
> There is no code for doing so, and although the implementation would use
> most of the code already there for UIO hotplug, which is basically related
> to unmapping PCI resources, and the interrupt part will be likely quite
> similar, the IOMMU unmapping requires more work.
>
> I dare to say this is the main reason for not having VFIO hotplug support
> right now. Maybe Tetsuya can confirm this or give us other reasons.
>
>
>>
>> Eelco
>>
>>
>>
>> On 07/02/17 10:29, Alejandro Lucero wrote:
>>
>> It seems none is working on this VFIO support.
>>
>> I will work on this if there is no reply to this thread saying the
>> opposite the next days.
>>
>> On Thu, Feb 2, 2017 at 12:58 PM, Eelco Chaudron <echaudron@redhat.com>
>> wrote:
>>
>>> On 02/02/17 13:05, Burakov, Anatoly wrote:
>>>
>>>> Hi Eelco,
>>>>
>>>> Please forgive me my ignorance on this matter, but doesn't it work at
>>>> the moment? I would assume that if regular PCI hotplug works (with
>>>> igb_uio), then so would hotplug with VFIO, as it basically utilizes the
>>>> same PCI infrastructure igb_uio does. That said, I'm not aware of any
>>>> patches submitted that had to do with VFIO and hotplug, so I guess the
>>>> answer is, not at the moment.
>>>>
>>>> Thanks,
>>>> Anatoly
>>>>
>>> I was asking as the documentation explicitly mentions its not supported.
>>> http://dpdk.org/doc/guides/prog_guide/port_hotplug_framework
>>> .html#hotplug
>>>
>>> - "To detach a port, the port should be backed by a device that igb_uio
>>> manages. VFIO is not supported."
>>>
>>> I could not find any specific reason why it's not supported, so if some
>>> one can explain this it would help also...
>>>
>>> Cheers,
>>>
>>> Eelco
>>>
>>>
>>>
>>
>>
>