ACK/Cmnt: [PATCH 0/6][Focal] 5.4 kernel: when iommu is on crashdump fails

[Stefan Bader]

On 06.04.21 19:12, Tim Gardner wrote:
> [SRU Justification]
> 
> BugLink: https://bugs.launchpad.net/bugs/1922738
> 
> When iommu is enabled crashdump fails to be collected because crash-kernel crashes.
> 
> See extended SRU justification in the bug report.

When all the detail is in the bug report, then just putting in random info which 
does not even make sense in some case, is rather unhelpful. The info that should 
be here is anything on a technical level which somehow is helping the 
reviewer(s). Whereas the SRU justification is targeted towards the SRU team 
which is less technical. So Ioanna, I think your regression analysis is great 
for kernel devs but could be slightly overwhelming for the SRU team. They also 
did update their documentation last year because "regression potential" was 
mis-understood a lot. What they would like to see is a hint on "how" things go 
wrong.

What I found with this set is that things become much clearer when looking at 
the complete delta of all 6 patches. That would also be something that is really 
helpful for a review. So ideally that would be part of the cover email. I have 
attached the diff to this email.

Looking at that it appears the main change is to move the delayed attachment 
from the function which looks a domain up to two other places which actually 
want a mapping. Overall this seems to a later stage. With that in mind the 
regression potential is whenever there is a deferred attachment (cannot say 
which case this since I did not dig much deeper here) and possibly then stack 
traces which show the two new calling functions somewhere.

For the patchset:

Acked-by: Stefan Bader <stefan.bader at canonical.com>
> 
> [Test Plan]
> Enable crashdump, cause a fault.
> 
> [Where problems could occur]
> Released in stable updates:
> linux-5.5.y
> 
> [Other Info]
> None
> 
> 

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