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

[Tim Gardner]

On 1/4/23 9:18 AM, Tim Gardner wrote:
> 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.
> 
Applied to j/k linux-aws. Thanks.

-rtg
-- 
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Tim Gardner
Canonical, Inc