[PATCH 4/6] drm/amd/amdgpu: Pin bos from imported dma-bufs to GTT.

[Christian König]

Am 29.03.2017 um 11:07 schrieb Michel Dänzer:
> On 29/03/17 04:14 PM, Christian König wrote:
>> Am 29.03.2017 um 02:27 schrieb raof at ubuntu.com:
>>> From: Christopher James Halse Rogers
>>> <christopher.halse.rogers at canonical.com>
>>>
>>> Attempting to migrate the bo will break the sharing of the buffer.
>>>
>>> Signed-off-by: Christopher James Halse Rogers
>>> <christopher.halse.rogers at canonical.com>
>>> CC: amd-gfx at lists.freedesktop.org
>> NAK on this one and the radeon version.
>>
>> We can't migrate the buffers to VRAM, but we shouldn't pin it either
>> cause that will lock down the GTT space used for it.
> Ah, good point, didn't think of that.
>
>
>> Instead you should modify amdgpu_bo_pin() and fail if anybody tries to
>> migrate a BO which has prime_shared_count != 0 to VRAM (you migth need
>> to add this for radeon).
> This would also need to be checked in the AMDGPU_GEM_OP_SET_PLACEMENT
> case of amdgpu_gem_op_ioctl, otherwise userspace can change
> prefered_domains to AMDGPU_GEM_DOMAIN_VRAM, and using the BO for GPU
> operations may move it to VRAM.

Good point as well, that indeed also needs to be forbidden.

> Or maybe there's a central place which can catch both of these cases
> (and any others).

At least of hand I can't think of any. But catching those two cases 
should be sufficient as far as I can see.

Christian.