Bug#1059969: linux-image-6.6.9-amd64: CONFIG_MODULE_COMPRESS_XZ=y breaks cpu frequency scaling governor kernel module
On Thu, 04 Jan 2024 17:16:57 +0800 Jy Deng <1700011628@pku.edu.cn>
wrote:
> Package: src:linux
> Version: 6.6.9-1
> Severity: normal
> Tags: patch
> X-Debbugs-Cc: 1700011628@pku.edu.cn
>
> Dear Maintainer,
>
> In short, current configuration of debian kernel makes some scaling
governors
> not usable, for example amd_pstate=passive Ondemand. Some small
changes to
> configuration can solve the problem.
>
> To sovle the problem there is two optional ways:
> 1. Change some configurations like CONFIG_CPU_FREQ_GOV_POWERSAVE to y
rather
> than m
> All the configuraion below needs to be chanegd to y:
> CONFIG_CPU_FREQ_GOV_POWERSAVE=y
> CONFIG_CPU_FREQ_GOV_USERSPACE=y
> CONFIG_CPU_FREQ_GOV_ONDEMAND=y
> CONFIG_CPU_FREQ_GOV_CONSERVATIVE=y
>
> 2. Change the configuration CONFIG_MODULE_COMPRESS_XZ=y to
> CONFIG_MODULE_COMPRESS_NONE=y
> Notice that CONFIG_MODULE_COMPRESS_XZ=y not only breaks cpu frequency
governors
> but also breaks make bindeb-pkg. See
> https://bugzilla.kernel.org/show_bug.cgi?id=218341
> So that choose this option can deal with this issue too.
>
> Two file attached is about the two ways above to fix the problem.
>
>
>
> Here is some explanation:
>
> Debian kernel used to set configuration as
CONFIG_MODULE_COMPRESS_NONE=y. but
> after 6.6 debian kernel configuration use CONFIG_MODULE_COMPRESS_XZ=y
to
> compress the kernel module. However, modules for cpu frequency
governors is not
> usable when it's module is compressed.
>
> For example, CONFIG_CPU_FREQ_GOV_POWERSAVE=m is fine to work if
> CONFIG_MODULE_COMPRESS_NONE=y , but if CONFIG_MODULE_COMPRESS_XZ=y is
set then
> powersave governor is unavailable. This problem is same to other cpu
frequency
> governor configurations like CONFIG_CPU_FREQ_GOV_ONDEMAND=m
>
> On the other hand, configuration like CONFIG_CPU_FREQ_GOV_POWERSAVE=y
build the
> governor into kernel rather than module, so that such problem does
not exist.
>
> Notice that such problem not only breaks scaling driver acpi-cpufreq,
but also
> breaks modules for example amd pstate.
Why do those config break when the compression config is enabled? That
sounds like a bug in the kernel for those features, have you reported
that upstream? At the very least, the configuration system should
automatically set those to built-in, or refuse the wrong combination
--
Kind regards,
Luca Boccassi
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