REGRESSION in 6.0-rc7 caused by patch "ARM/dma-mapping: use dma-direct unconditionally"

[Thorsten Leemhuis]

Hi, this is your Linux kernel regression tracker.

On 30.09.22 15:10, Marek Behún wrote:
> Hello Linus, Arnd, Robin and Christoph,
> 
> I just bisected a regression on Turris Omnia (Armada 385), wherein the
> system hangs shortly after init is run, to commit
> 
>   ae626eb97376 ("ARM/dma-mapping: use dma-direct unconditionally")
>   https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=ae626eb97376

Thx for the report. I briefly looked into this and noticed this week
(IOW: after rc7) there was the change 7bea67a99430 ("ARM: dts:
integrator: Fix DMA ranges") that has a fixes tag for ae626eb97376. This
is not my area of expertise, but it made me wonder if it in any way
might be relevant to this issue?

Anyway, for the rest of this mail:
[TLDR: I'm adding this regression report to the list of tracked
regressions; all text from me you find below is based on a few templates
paragraphs you might have encountered already already in similar form.]

> In order to fix the regression, I had to revert this commit and
> subsequent 3 commits:
>   ae626eb97376 ("ARM/dma-mapping: use dma-direct unconditionally")
>   42998ef08aba ("ARM/dma-mapping: drop .dma_supported for IOMMU ops")
>   d563bccfa35b ("ARM/dma-mapping: consolidate IOMMU ops callbacks")
>   4136ce90f079 ("ARM/dma-mapping: merge IOMMU ops")
> in reverse order, of course:
>   git revert 4136ce90f079
>   git revert d563bccfa35b
>   git revert 42998ef08aba
>   git revert ae626eb97376
> 
> Christoph, Robin, since you are the authors of these commits, do you
> have any idea what could be happening? Are we able to fix this without
> reverting those commits, before 6.0?

CCing the regression mailing list, as it should be in the loop for all
regressions, as explained here:
https://www.kernel.org/doc/html/latest/admin-guide/reporting-issues.html

Thanks for the report. To be sure below issue doesn't fall through the
cracks unnoticed, I'm adding it to regzbot, my Linux kernel regression
tracking bot:

#regzbot ^introduced ae626eb97376
#regzbot title arm: Turris Omnia (Armada 385) hangs shortly after init
is run,
#regzbot ignore-activity

This isn't a regression? This issue or a fix for it are already
discussed somewhere else? It was fixed already? You want to clarify when
the regression started to happen? Or point out I got the title or
something else totally wrong? Then just reply -- ideally with also
telling regzbot about it, as explained here:
https://linux-regtracking.leemhuis.info/tracked-regression/

Reminder for developers: When fixing the issue, add 'Link:' tags
pointing to the report (the mail this one replies to), as explained for
in the Linux kernel's documentation; above webpage explains why this is
important for tracked regressions.

Ciao, Thorsten (wearing his 'the Linux kernel's regression tracker' hat)

P.S.: As the Linux kernel's regression tracker I deal with a lot of
reports and sometimes miss something important when writing mails like
this. If that's the case here, don't hesitate to tell me in a public
reply, it's in everyone's interest to set the public record straight.