Re: sun4v+DMA related boot crash on 4.13-git

From: Tushar Dave
Date: Tue Jul 11 2017 - 23:43:53 EST

On 07/11/2017 05:34 PM, David Miller wrote:
From: Tushar Dave <tushar.n.dave@xxxxxxxxxx>
Date: Tue, 11 Jul 2017 15:38:21 -0700

On 07/11/2017 02:48 PM, Meelis Roos wrote:
I tested yesterdayd 4.12+git on sparc64 to see if the sparc merge
fine, and on all of my sun4v machines (T1000, T2000, T5120) it crashed
on boot with DMA-related stacktrace (below). Allt he machines are
physical machines, not VM-s. Older sun4 machines do not exhibit this

Maybae DMA APi realted, maybe sparc64. Will try to bisect when I get
I see whats going on with panic. I will reproduce locally. Will get
This patch should fix panic. Please give it a try.

Yes, this patch fixes it. Thank you for fixing it quickly!
Thanks for testing. Patch sent for sparc-next.
Why sparc-next - it should go into 4.13 since 4.13 would break all
niagara1 and niagara2 systems otherwise?This is sparc arch fix so I
used sparc tree(in this case for sparc-next).
I am open to maintainers suggestions. Thanks.

If the bug is in Linus's tree the fix must target 'sparc' not


Yes, indeed the bug is in Linus's tree. However, 'sparc' tree doesn't have DMA API change (e.g. commit b02c2b0bfd7ae) yet that introduced the panic. Looks like the DMA API changes have not merged into 'sparc' tree yet. In other words, 'sparc' tree doesn't have mentioned panic issue, nothing to fix there!
However, 'sparc-next' is up to date (or more close to) linus tree and has DMA API change that cause mentioned panic issue. So I have send patch targeted for sparc-next.

Let me know what should be the best tree to get this fix in and I will send v2.


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