amdgpu/TTM oopses since merging swiotlb_dma_ops into the dma_direct code

Sibren Vasse sibren at
Thu Jan 10 15:26:43 UTC 2019

On Thu, 10 Jan 2019 at 14:57, Christoph Hellwig <hch at> wrote:
> On Thu, Jan 10, 2019 at 10:59:02AM +0100, Michel Dänzer wrote:
> >
> > Hi Christoph,
> >
> >
> > (please ignore comments #6-#9) was
> > bisected to your commit 55897af63091 "dma-direct: merge swiotlb_dma_ops
> > into the dma_direct code". Any ideas?
> From the trace it looks like we git the case where swiotlb tries
> to copy back data from a bounce buffer, but hits a dangling or NULL
> pointer.  So a couple questions for the submitter:
My apologies if I misunderstand something, this subject matter is new to me.

>  - does the system have more than 4GB memory and thus use swiotlb?
My system has 8GB memory. The other report on the bug tracker had 16GB.

>    (check /proc/meminfo, and if something SWIOTLB appears in dmesg)
Can I grep dmesg for a string?

>  - does the device this happens on have a DMA mask smaller than
>    the available memory, that is should swiotlb be used here to start
>    with?
It's a MSI Radeon RX 570 Gaming X 4GB. The other report was a RX 580.
lshw output:



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