[PATCH 0/2][SRU][j/k linux-aws] AWS: Disable CONFIG_CMA

[Tim Gardner]

BugLink: https://bugs.launchpad.net/bugs/1990167

SRU Justification

[Impact]

When launching large arm64 instances on the focal or jammy ami, cma allocation errors appear in the dmesg out:

[ 0.063255] cma: cma_alloc: reserved: alloc failed, req-size: 4096 pages, ret: -12

As far as I can tell, this does not impact instance launch in a meaningful way,
but I am unsure of the other implications of this. I was able to confirm that
these messages are only present in 5.15, as they do not show up in the bionic
image, and rolling back focal to linux-aws 5.4 avoids them as well.

This was present in at least 2 instance types and only appears to pop up in large
sizes (2x4 does not produce them, 64x124 (c6gn.16xlarge) does)

This could be as simple as just disabling CMA in the linux-aws pkg, as it appears
this is already the case in linux-azure(LP: #1949770).

Attaching dmesg out to the report.

[Test Plan]

# Replication
+ Launch a large arm64 instance (c6gn.16xlarge)
+ Observe the messages in kern.log / dmesg

[Where things could go wrong]

External drivers that depend on CMA will no longer compile.