Question about: AMD-Vi: Event logged [IO_PAGE_FAULT ...

[Raimonds Cicans]

Hello.

After kernel upgrade (3.13 => 3.17) I started to receive following 
string in my logs:
AMD-Vi: Event logged [IO_PAGE_FAULT device=08:00.0 domain=0x001c 
address=0x0000000001355000 flags=0x0000]

I would like to deeper understand this problem, so it
would be nice if some body can fix my assumptions and
answer my questions.


Assumptions:

1) This message is generated by AMD IOMMU subsystem
     because PCIe device 08:00.0 tried to access memory
     region which was not mapped to any real memory
     (lspci show that this device is DVB-S2 receiver card
      TBS 6981)

2) Because flags are 0 and because in general receivers
    write to memory not read from memory it is memory
    write operation

3) Possible causes:
    a) memory region was never mapped
    b) device accessed memory region before it was mapped
    c) device accessed memory region after it was unmapped

3) Suspects:
     a) kernel's DMA subsystem: very unlikely
     b) kernel's IOMMU subsystem: very unlikely
     c) AMD IOMMU driver: unlikely? - i had problems with AMD IOMMU
         itself in kernels 3.14 - 3.17 (AMD-Vi: Completion-Wait loop 
timed out)
         So maybe this problem not fully fixed?
     d) Receiver's driver: likely


Questions:
1) What 'domain=0x001c' mean?
2) Where I can find definition of possible flags?
3) What kind of address is written in message?
     - physical?
     - virtual?
     - address from devices point of view?


Thank you.


Raimonds Cicans
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