Re: [PATCH v11 10/22] vfio iommu type1: Add support for mediated devices

[Alexey Kardashevskiy <aik@ozlabs.ru>]

On 15/11/16 17:33, Kirti Wankhede wrote:
> 
> 
> On 11/15/2016 10:47 AM, Alexey Kardashevskiy wrote:
>> On 08/11/16 17:52, Alexey Kardashevskiy wrote:
>>> On 05/11/16 08:10, Kirti Wankhede wrote:
>>>> VFIO IOMMU drivers are designed for the devices which are IOMMU capable.
>>>> Mediated device only uses IOMMU APIs, the underlying hardware can be
>>>> managed by an IOMMU domain.
>>>>
>>>> Aim of this change is:
>>>> - To use most of the code of TYPE1 IOMMU driver for mediated devices
>>>> - To support direct assigned device and mediated device in single module
>>>>
>>>> This change adds pin and unpin support for mediated device to TYPE1 IOMMU
>>>> backend module. More details:
>>>> - vfio_pin_pages() callback here uses task and address space of vfio_dma,
>>>>   that is, of the process who mapped that iova range.
>>>> - Added pfn_list tracking logic to address space structure. All pages
>>>>   pinned through this interface are trached in its address space.
>>>> - Pinned pages list is used to verify unpinning request and to unpin
>>>>   remaining pages while detaching the group for that device.
>>>> - Page accounting is updated to account in its address space where the
>>>>   pages are pinned/unpinned.
>>>> -  Accouting for mdev device is only done if there is no iommu capable
>>>>   domain in the container. When there is a direct device assigned to the
>>>>   container and that domain is iommu capable, all pages are already pinned
>>>>   during DMA_MAP.
>>>> - Page accouting is updated on hot plug and unplug mdev device and pass
>>>>   through device.
>>>>
>>>> Tested by assigning below combinations of devices to a single VM:
>>>> - GPU pass through only
>>>
>>> This does not require this patchset, right?
>>>
> 
> Sorry I missed this earlier.
> This testing is required for this patch, because this patch touches code
> that is used for direct device assignment. Also for page accounting, all
> cases are considered i.e. when there is only pass through device in a
> container, when there is pass through device + vGPU device in a
> container. Also have to test that pages are pinned properly when device
> is hotplugged. In that case vfio_iommu_replay() is called to take
> necessary action.

So in this particular test you are only testing that the patchset did not
break the already existing functionality, is that correct?


> 
>>>> - vGPU device only
>>>
>>> Out of curiosity - how exactly did you test this? The exact GPU, how to
>>> create vGPU, what was the QEMU command line and the guest does with this
>>> passed device? Thanks.
>>
>> ping?
>>
> 
> I'm testing this code with M60, with custom changes in our driver.


Is this shared anywhere? What does the mediated driver do? Can Tesla K80 do
the same thing, or [10de:15fe] (whatever its name is)?


> Steps how to create mediated device are listed in
> Documentation/vfio-mediated-device.txt for sample mtty driver. Same
> steps I'm following for GPU. Quoting those steps here for you:


Nah, I saw this, I was wondering about actual hardware :) Like when you say
"tested with vGPU" - I am wondering what is passed to the guest and how the
guest is actually using it.


> 
> 2. Create a mediated device by using the dummy device that you created
> in the
>    previous step.
> 
>    # echo "83b8f4f2-509f-382f-3c1e-e6bfe0fa1001" >      \
> 
> /sys/devices/virtual/mtty/mtty/mdev_supported_types/mtty-2/create
> 
> 3. Add parameters to qemu-kvm.
> 
>    -device vfio-pci,\
>     sysfsdev=/sys/bus/mdev/devices/83b8f4f2-509f-382f-3c1e-e6bfe0fa1001




-- 
Alexey