[Bug 215740] kernel warning: DMA-API: xhci_hcd: cacheline tracking EEXIST, overlapping mappings aren't supported

[bugzilla-daemon@kernel.org]

https://bugzilla.kernel.org/show_bug.cgi?id=215740

--- Comment #11 from Alan Stern (stern@rowland.harvard.edu) ---
I don't think it has anything to do with the init3: section.  The stack trace
shows that the problem stems from hub_ext_port_status(), probably called by
port_event() within hub_event().  And the place where hub_ext_port_status()
calls usb_control_msg() indirectly is protected by a mutex!

The I/O buffer being mapped multiple times is hub->status->port, and it doesn't
get used anywhere else in the hub driver AFAICS.  (There is a comment about the
phy driver also using that buffer; I don't know what it refers to.)

[It would be easier to track this down if the DMA subsystem would cause these
erroneous mappings to fail instead of pretending that they have succeeded. 
Grumble...]

I'm stumped.  I'll try to find time to reproduce it on my own system.  Probably
would have noticed it before now if I had tried connecting an external hub
recently, but that just hasn't come up.

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