Re: Question about supporting AMD eGPU hot plug case

["Christian König" <christian.koenig@amd.com>]

Am 11.03.21 um 23:40 schrieb Andrey Grodzovsky:
> [SNIP]
>>> The expected result is they all move closer to the start of PCI address
>>> space.
>>>
>>
>> Ok, I updated as you described. Also I removed PCI conf command to stop
>> address decoding and restart later as I noticed PCI core does it itself
>> when needed.
>> I tested now also with graphic desktop enabled while submitting
>> 3d draw commands and seems like under this scenario everything still
>> works. Again, this all needs to be tested with VRAM BAR move as then
>> I believe I will see more issues like handling of MMIO mapped VRAM 
>> objects (like GART table). In case you do have an AMD card you could 
>> also maybe give it a try. In the meanwhile I will add support to 
>> ioremapping of those VRAM objects.
>>
>> Andrey
>
> Just an update, added support for unmaping/remapping of all VRAM
> objects, both user space mmaped and kernel ioremaped. Seems to work
> ok but again, without forcing VRAM BAR to move I can't be sure.
> Alex, Chsristian - take a look when you have some time to give me some
> initial feedback on the amdgpu side.
>
> The code is at 
> https://cgit.freedesktop.org/~agrodzov/linux/log/?h=yadro%2Fpcie_hotplug%2Fmovable_bars_v9.1

Mhm, that let's userspace busy retry until the BAR movement is done.

Not sure if that can't live lock somehow.

Christian.

>
> Andrey