APPLIED/Cmnt: [SRU][X/aws][PATCH v2 0/1] aws: revert change to support instance types > 255 cpu cores

[Stefan Bader]

On 11.03.21 09:01, Andrea Righi wrote:
> BugLink: https://bugs.launchpad.net/bugs/1918590
> 
> [Impact]
> 
> In LP: #1913739 we applied a fix to properly detect the right amount of
> cores in AWS large instance types (> 255). However, this fix seems to
> work properly only with kernels > 4.4. Even if it doesn't seem to
> introduce any failure or regression, it is probably just safer to revert
> this commit in the Xenial kernel, and keep it on the other kernels (> 4.4).
> 
> [Test plan]
> 
> Boot an instance type with > 255 cpus and check the amount of cores
> detected.
> 
> [Fix]
> 
> Revert commit:
> 
>    561ef22a7d396289a1c5a1d18057ccdf9bb59826 ("iommu/vt-d: Gracefully handle DMAR units with no supported address widths")
> 
> [Regression potential]
> 
> Reverting the commit simply restores the old behavior, so we won't be
> able to detect the right amount of CPUs in large instances, but we are
> sure that we won't also introduce any potential failure or regressions
> by restoring the previous behavior. And this is affecting only the
> Xenial kernel, that is approaching to EOL.
> 
> ChangeLog (v1 -> v2):
>    - create a new bug instead of re-using the old one when the original
>      fix was applied
> 
> 
Applied to xenial:linux-aws/master. I took the ACKs from v1 since there was no 
difference in the content other than the bug report. Thanks.

-Stefan

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