DMA Faults with XHCI driver

["Jörg Rödel" <jroedel@suse.de>]

Hi Mathias,

here is a report about something strange happening on my system after a
recent IOMMU change. I am starting to see this message at boot:

	xhci_hcd 0000:02:00.0: AMD-Vi: Event logged [IO_PAGE_FAULT domain=0x000f address=0xff00ffffffefe000 flags=0x0000]

It means that the XHCI device tried a DMA access at address
0xff00ffffffefe000, which was not mapped in the IOMMU page table.

Devices attached to that XHCI controller will not work after that
message.

There is a related change in the IOMMU code which uncovered this, the
change basically lets the IOMMU dma-allocator not allocate below 4GB by
default, but use the whole space covered by the DMA mask.

To better track this down I limited the DMA-space to 48 bits, and the
message still shows up.

I think this might be a problem in the XHCI driver, e.g. it might mangle
an allocated DMA address somehow if it is bigger than 32 bit.

The device behind 0000:02:00.0 is a

	02:00.0 USB controller: Advanced Micro Devices, Inc. [AMD] Device 43d0 (rev 01)

Please let me know what I can do to help tracking this down.

Regards,

-- 
Jörg Rödel
jroedel@suse.de

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