ACK: [SRU][PULL v4][G/aws] config changes to improve hibernation on Xen instance types

[Kleber Souza]

On 05.11.20 19:05, Andrea Righi wrote:
> BugLink: https://bugs.launchpad.net/bugs/1902926
> BugLink: https://bugs.launchpad.net/bugs/1732512
> BugLink: https://bugs.launchpad.net/bugs/1879711
> 
> [Impact]
> 
> The 5.8 kernel (groovy) is not still 100% reliable with hibernation,
> especially on the Xen instance type. However, re-aligning the config
> options as much as possible with the 5.4 kernel (focal) allows to
> hibernate and resume with a success rate close to 100% (according to our
> tests on the AWS cloud).
> 
> [Test case]
> 
>   - spin up an AWS instance (for example a c4.8xlarge instance type)
>   - run a memory stress test
>   - hibernate
>   - resume
>   - verify that the system has been resumed correctly and the memory
>     stress test is still running
> 
> [Fix]
> 
> The following fixes must be applied to improve hibernation/resume
> reliability:
> 
>   - disable CONFIG_SUSPEND (suspend to memory is not supported in AWS and
>     it can introduce a deadlock condition with the Xen hibernation layer)
>   - make sure CONFIG_DMA_CMA is disabled (this introduces another
>     deadlock condition with Xen)
>   - disable CONFIG_FB_HYPERV: this would enable CONFIG_DMA_CMA and we
>     don't want that (to prevent the Xen deadlock); moreover this driver
>     is not needed at all in the AWS environment
>   - disable CONFIG_XEN_FBDEV_FRONTEND: this is also not required in the
>     AWS environement and it has the potential of breaking hibernation
>   - disable CONFIG_INPUT_XEN_KBDDEV_FRONTEND
>   - disable CONFIG_XEN_BALLOON
>   - make sure xen-netfront is *not* compiled as a module, otherwise
>     it seems that the network is not properly resumed on the t2 instance
>     types (enforce that in the annotations file to prevent changing it
>     again in the future)
>   - remove all sound-related modules (not really needed in the AWS cloud,
>     they were also disabled on 5.4)
> 
> [Regression potential]
> 
> These are all .config changes. With these changes we are basically
> re-aligning with the previous 5.4 settings and we have experimentally
> verified (tests) that these changes are increasing the success rate of
> hibernation. So the regression potential is minimal.
> 
> Changes v3 -> v4:
>   - enforce xen-netfront to be statically compiled in the kernel
>     (otherwise the network is not properly resumed on the t2 instance types)
> 
> ----------------------------------------------------------------
> 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 6f973e789d4bec33c42a21dcbddf3a8a5596cb45:
> 
>    UBUNTU: [Config] [aws] remove all sound-related modules (2020-11-05 18:39:59 +0100)

Re-aligning the configs with f/aws makes total sense to me.

Acked-by: Kleber Sacilotto de Souza <kleber.souza at canonical.com>

> 
> ----------------------------------------------------------------
> Andrea Righi (7):
>        UBUNTU: [Config] [aws] make sure CONFIG_FB_HYPERV is disabled
>        UBUNTU: [Config] [aws] make sure CONFIG_SUSPEND is disabled
>        UBUNTU: [Config] [aws] disable CONFIG_XEN_FBDEV_FRONTEND
>        UBUNTU: [Config] [aws] disable CONFIG_INPUT_XEN_KBDDEV_FRONTEND
>        UBUNTU: [Config] [aws] disable CONFIG_XEN_BALLOON on amd64
>        UBUNTU: [Config] [aws] enforce CONFIG_XEN_NETDEV_FRONTEND
>        UBUNTU: [Config] [aws] remove all sound-related modules
> 
>   debian.aws/abi/5.8.0-1010.10/amd64/aws.modules | 478 -----------------
>   debian.aws/abi/5.8.0-1010.10/arm64/aws.modules | 479 -----------------
>   debian.aws/config/amd64/config.common.amd64    |   3 +-
>   debian.aws/config/annotations                  | 655 +----------------------
>   debian.aws/config/arm64/config.common.arm64    |   3 +-
>   debian.aws/config/config.common.ubuntu         | 693 +------------------------
>   debian.aws/control.d/aws.inclusion-list        |   1 -
>   7 files changed, 21 insertions(+), 2291 deletions(-)
>