not seeing PMIs on AMD 16h family processor with 3.4 or 3.15

[Prasad Koya]

Hi

We are not seeing performance monitoring interrupts on AMD eKabini CPU
(family 16h processor). Tried both 3.4 and 3.15 kernels. If there is
more relevant group for this, I could post it there.

When I write to 0xc001_0004 (as given in AMD spec for core perf
counters) counter I see that it overflows fine and it starts counting
back from 0. However I don't see any NMI after oerflow. I also checked
0xc001_0000 and its value is 0x530076, which shows that the NMI is
enabled.


On 3.15 kernel I see this message on console:

[67044.084213] perf interrupt took too long (2529 > 2500), lowering
kernel.perf_event_max_sample_rate to 50000
[146301.023898] Uhhuh. NMI received for unknown reason 31 on CPU 1.
[146301.023952] Do you have a strange power saving mode enabled?
[146301.023991] Dazed and confused, but trying to continue

Anyone else seeing this?

Thank you.
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