Re: [PATCH 06/10] swiotlb: use swiotlb_map_page in swiotlb_map_sg_attrs

[John Stultz]

On Thu, Nov 8, 2018 at 11:49 PM, Christoph Hellwig <hch@xxxxxx> wrote:
> On Tue, Nov 06, 2018 at 05:27:14PM -0800, John Stultz wrote:
>> But at that point if I just re-apply "swiotlb: use swiotlb_map_page in
>> swiotlb_map_sg_attrs", I reproduce the hangs.
>>
>> Any suggestions for how to further debug what might be going wrong
>> would be appreciated!
>
> Very odd.  In the end map_sg and map_page are defined to do the same
> things to start with.  The only real issue we had in this area was:
>
> "[PATCH v2] of/device: Really only set bus DMA mask when appropriate"
>
> so with current mainline + that you still see a problem, and if you
> rever the commit we are replying to it still goes away?

Just to confirm, as of 4.20-rc2 (which includes the of/device patch
above), I'm still seeing this issue, but it isn't as reliable to
reproduce as before.

With "swiotlb: use swiotlb_map_page in swiotlb_map_sg_attrs" reverted
(along with the dependent swiotlb patches) it doesn't seem to trigger
(no matter what I try).  But re-applying that patch it tends to
trigger by itself at boot up, but sometimes I have to run "find /" to
trigger the io hang/stall.

thanks
-john