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

[Andrea Righi]

Will send a new patch soon, creating a new bug instead of re-using the
old one.

-Andrea

On Tue, Feb 23, 2021 at 05:36:06PM +0100, Andrea Righi wrote:
> BugLink: https://bugs.launchpad.net/bugs/1913739
> 
> [Impact]
> 
> The following commit was required to properly detect the right amount of
> cores in large instance types (with > 255 cpus):
> 
>  561ef22a7d396289a1c5a1d18057ccdf9bb59826 "iommu/vt-d: Gracefully handle DMAR units with no supported address widths"
> 
> However, this patch seems to work correctly only with kernels > 4.4.
> Considering the imminent EOL for this kernel it probably makes sense to
> drop this patch for now, to prevent potential regressions.
> 
> [Test case]
> 
> Tests performed in the AWS cloud, the test case simply consists of
> checking the amount of available cpus (running `nproc`).
> 
> [Fix]
> 
> Revert commit 561ef22a7d396289a1c5a1d18057ccdf9bb59826.
> 
> [Regression potential]
> 
> This change reverts a previously applied fix (that doesn't actually fix
> the problem), so the only downside is simply that not all the available
> cores will be detected on the large instance types (basically we are
> simply reverting to an old behavior).