On 16/10/2017 20:23, Robin Murphy wrote:
> On 16/10/17 12:54, Hao Wei Tee wrote:
>> On 12/10/2017 21:36, Mathias Nyman wrote:
>>> You could try booting with xhci_hcd.dyndbg=+p added to the kernel command line.
>>
>> I can't find anything relevant... Hmm.
>
> Is your VL805 on the motherboard or an add-on card? One other possibly
> important difference that comes to mind is that on my arm64 system Linux
> is the only agent to ever touch the xHCI - UEFI doesn't even try to
> probe it. It seems likely that a full-featured PC firmware might have
> been more hands-on, especially if the controller is on-board.
>
> It seems noteworthy that these RMRRs are within about 10MB of the
> faulting address...
>
> ...and that correspondingly for this to be a Linux-allocated IOVA would
> mean over 540MB having been mapped for DMA already, which seems somewhat
> less likely than it being some leftover physical address from firmware.
>
> Can you try instrumenting xhci_segment_alloc() to get an idea of what
> the actual DMA addresses of the various queues are at this point?
>
> Robin
Sorry for taking so long, I got caught up with other stuff..
Anyway, I think you may be right about the addresses coming from UEFI. With the IOMMU
on, xhci_segment_alloc is never called (the DMA faults happen in very early xHCI init).
With the IOMMU off, the allocated segments look something like this:
xhci_segment_alloc() = (xhci_segment) {
.dma = 0x00000002136b9000
.bounce_dma = 0x0000000000000000
.bounce_buf = (null)
.bounce_offs = 0
.bounce_len = 0
}
xhci_segment_alloc() = (xhci_segment) {
.dma = 0x00000002136bb000
.bounce_dma = 0x0000000000000000
.bounce_buf = (null)
.bounce_offs = 0
.bounce_len = 0
}
xhci_segment_alloc() = (xhci_segment) {
.dma = 0x000000021377e000
.bounce_dma = 0x0000000000000000
.bounce_buf = (null)
.bounce_offs = 0
.bounce_len = 0
}
xhci_segment_alloc() = (xhci_segment) {
.dma = 0x0000000213776000
.bounce_dma = 0x0000000000000000
.bounce_buf = (null)
.bounce_offs = 0
.bounce_len = 0
}
xhci_segment_alloc() = (xhci_segment) {
.dma = 0x00000002126ec000
.bounce_dma = 0x0000000000000000
.bounce_buf = ffff9887d4d91d30
.bounce_offs = 0
.bounce_len = 0
}
xhci_segment_alloc() = (xhci_segment) {
.dma = 0x00000002126ed000
.bounce_dma = 0x0000000000000000
.bounce_buf = ffff9887d4d91140
.bounce_offs = 0
.bounce_len = 0
}
.. which is nowhere near the address the DMA faults occur at,
although I'm not sure if having the IOMMU on affects this (??).
Thanks.
--
Hao Wei
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