NACK: [SRU][PULL][G/aws] config changes to fix hibernation on Xen instance types

[Andrea Righi]

NACK-ing this one for now.

After more chatting about this, we decided to proceed in a more
incremental way, rather than apply a bulk of config changes.

I will send another patch set to enable only the 3 config options we
know *for sure* that are required and then I will open a new bug to
determine which other options exactly are required to improve the
success rate of hibernation.

-Andrea

On Wed, Nov 04, 2020 at 01:00:22PM +0100, Andrea Righi wrote:
> BugLink: https://bugs.launchpad.net/bugs/1732512
> BugLink: https://bugs.launchpad.net/bugs/1879711
> 
> [Impact]
> 
> After moving to 5.8 the config for the AWS kernel has been re-generated
> starting from the generic 5.8 kernel. However, in the process, we missed
> some important config options that are required to properly support
> hibernation, especially on Xen instance types.
> 
> Re-align the config starting from a 5.4 kernel and report explicitly in
> the annotations file the relevant config options required by
> hibernation.
> 
> Also get rid of some modules that were not enabled in 5.4 and are also
> not required in 5.8. This makes the kernel smaller and allows to provide
> a faster boot time.
> 
> These changes have been tested in the AWS environment using Xen and KVM
> instance types. Without these config changes hibernation is currently
> broken on certain instance types.
> 
> [Test case]
> 
>  - start a Xen-based instance (i.e., c4.8xlarge)
>  - start a memory stress test on it
>  - hibernate & resume
>  - verify that the instance has been properly resumed and the memory
>    stress test is still running
> 
> [Fix]
> 
> Re-align as much as possible with the config options used in 5.4 and
> also get rid of some additional modules that were enabled and that are
> not required.
> 
> [Regression potential]
> 
> The risk of regression is to disable certain modules/drivers that are
> potentially required, but without these changes hibernation is currently
> broken in many Xen instance types, so it is less risky to use these new
> config options.
> 
> ----------------------------------------------------------------
> The following changes since commit f352dd559e7c0ab7aa8db3b91f698e4cbbfbcbe3:
> 
>   UBUNTU: Ubuntu-aws-5.8.0-1011.11 (2020-10-22 11:23:44 +0200)
> 
> are available in the Git repository at:
> 
>   git://git.launchpad.net/~arighi/ubuntu/+source/linux-aws/+git/groovy tags/aws-config-update
> 
> for you to fetch changes up to 22c3b97f3738040e278672b2d230526307ca8900:
> 
>   UBUNTU: [Config] [aws] make sure CONFIG_XEN_FBDEV_FRONTEND is disabled (2020-11-04 12:57:59 +0100)
> 
> ----------------------------------------------------------------
> Andrea Righi (4):
>       UBUNTU: [Config] [aws] re-align configs with kernel 5.4 aws
>       UBUNTU: [Config] [aws] make sure CONFIG_FB_HYPERV is disabled
>       UBUNTU: [Config] [aws] make sure CONFIG_SUSPEND is disabled
>       UBUNTU: [Config] [aws] make sure CONFIG_XEN_FBDEV_FRONTEND is disabled
> 
>  debian.aws/abi/5.8.0-1010.10/amd64/aws.modules |  1875 +--
>  debian.aws/abi/5.8.0-1010.10/arm64/aws.modules |   969 +-
>  debian.aws/config/amd64/config.common.amd64    |   163 +-
>  debian.aws/config/annotations                  | 18342 +++++++++++------------
>  debian.aws/config/arm64/config.common.arm64    |   163 +-
>  debian.aws/config/config.common.ubuntu         |  2390 +--
>  6 files changed, 9212 insertions(+), 14690 deletions(-)