NACK/Cmnt: [SRU][O:aws][PATCH 1/1] UBUNTU: SAUCE: arm64: Kconfig: Disable ACPI_HOTPLUG_CPU

[Jacob Martin]

On Wed, Dec 11, 2024 at 04:00:44PM +0900, Koichiro Den wrote:
> BugLink: https://bugs.launchpad.net/bugs/2088047
> 
> On AWS EC2 a1.metal and c6g.8xlarge instances, issues caused by unexpected
> discrepancies within ACPI table have been observed (LP: #2088047). Given
> the possibility of encountering other problematic ACPI table patterns, this
> patch entirely disable ACPI_HOTPLUG_CPU on arm64 instances until those are
> fixed at the firmware level.
> 
> This essentially reverts the following two commits:
>   9d0873892f4d ("arm64: Kconfig: Enable hotplug CPU on arm64 if
>                  ACPI_PROCESSOR is enabled.")
>   46800e38ef0e ("arm64: Kconfig: Fix dependencies to enable
>                  ACPI_HOTPLUG_CPU")
> 
> Signed-off-by: Koichiro Den <koichiro.den at canonical.com>
> ---
>  arch/arm64/Kconfig               | 1 -
>  debian.master/config/annotations | 2 +-
>  2 files changed, 1 insertion(+), 2 deletions(-)
> 
> diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig
> index 365c106c4872..fff8e671348f 100644
> --- a/arch/arm64/Kconfig
> +++ b/arch/arm64/Kconfig
> @@ -5,7 +5,6 @@ config ARM64
>  	select ACPI_CCA_REQUIRED if ACPI
>  	select ACPI_GENERIC_GSI if ACPI
>  	select ACPI_GTDT if ACPI
> -	select ACPI_HOTPLUG_CPU if ACPI_PROCESSOR && HOTPLUG_CPU
>  	select ACPI_IORT if ACPI
>  	select ACPI_REDUCED_HARDWARE_ONLY if ACPI
>  	select ACPI_MCFG if (ACPI && PCI)
> diff --git a/debian.master/config/annotations b/debian.master/config/annotations
> index ea48d9399a4f..f705f50b1e56 100644
> --- a/debian.master/config/annotations
> +++ b/debian.master/config/annotations
> @@ -958,7 +958,7 @@ CONFIG_ACPI_GENERIC_GSI                         policy<{'arm64': 'y', 'riscv64':
>  CONFIG_ACPI_GTDT                                policy<{'arm64': 'y'}>
>  CONFIG_ACPI_HED                                 policy<{'amd64': 'y', 'arm64': 'y', 'riscv64': 'y'}>
>  CONFIG_ACPI_HMAT                                policy<{'amd64': 'y', 'arm64': 'y', 'riscv64': 'y'}>
> -CONFIG_ACPI_HOTPLUG_CPU                         policy<{'amd64': 'y', 'arm64': 'y'}>
> +CONFIG_ACPI_HOTPLUG_CPU                         policy<{'amd64': 'y', 'arm64': '-'}>
>  CONFIG_ACPI_HOTPLUG_IOAPIC                      policy<{'amd64': 'y'}>
>  CONFIG_ACPI_HOTPLUG_MEMORY                      policy<{'amd64': 'y', 'arm64': 'y', 'riscv64': 'y'}>
>  CONFIG_ACPI_I2C_OPREGION                        policy<{'amd64': 'y', 'arm64': 'y', 'riscv64': 'y'}>
> -- 
> 2.43.0
> 

Since this is to be applied to the Oracular AWS kernel, it seems to me like
this annotations change should exist as an override in the
debian.aws/config/annotations file instead.

Also, I think this would work better as two separate patches, one to make the
arm64 Kconfig change, and another "UBUNTU: [Config]" patch to make the
annotations change.

Jacob