dual RX460 result in logspam about P2P DMA

[Richard Dietrich Wachler]

Excuse my novicesness,

i use 2 RX460 on a KGPE-D16 server board to drive 4 displays.

02:00.0 VGA compatible controller: Advanced Micro Devices, Inc. 
[AMD/ATI] Baffin [Radeon RX 460/560D / Pro 
450/455/460/555/555X/560/560X] (rev cf)
06:00.0 VGA compatible controller: Advanced Micro Devices, Inc. 
[AMD/ATI] Baffin [Radeon RX 460/560D / Pro 
450/455/460/555/555X/560/560X] (rev cf)

There is a noticeable mouse lag on the second card, so i investigated 
and got logspam 20 times a second like this:

May 15 15:58:27 xx kernel: amdgpu 0000:02:00.0: cannot be used for 
peer-to-peer DMA as the client and provider (0000:06:00.0) do not share 
an upstream bridge or whitelisted host bridge

It seems there is no real way to disable the check or disable P2P DMA 
completely. Or maybe my problem is elsewhere?

Thanks for any hints, i havent found anything about this as its quite a 
new feature.

Richard Wachler