Small question Alex Deucher or Christian may answer: is it normal ring 5 is
completely in a different GPU's memory address area?
[    9.353518] radeon 0000:01:00.0: fence driver on ring 0 use gpu addr
0x00000000c0000c00 and cpu addr 0xffff880411a25c00
[    9.353519] radeon 0000:01:00.0: fence driver on ring 1 use gpu addr
0x00000000c0000c04 and cpu addr 0xffff880411a25c04
[    9.353521] radeon 0000:01:00.0: fence driver on ring 2 use gpu addr
0x00000000c0000c08 and cpu addr 0xffff880411a25c08
[    9.353522] radeon 0000:01:00.0: fence driver on ring 3 use gpu addr
0x00000000c0000c0c and cpu addr 0xffff880411a25c0c
[    9.353524] radeon 0000:01:00.0: fence driver on ring 4 use gpu addr
0x00000000c0000c10 and cpu addr 0xffff880411a25c10
[    9.356425] radeon 0000:01:00.0: fence driver on ring 5 use gpu addr
0x0000000000075a18 and cpu addr 0xffffc90015fb5a18

rings 0 to 4 are all in the same gpu address subset, but not ring 5?