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Bug#1059969: linux-image-6.6.9-amd64: CONFIG_MODULE_COMPRESS_XZ=y breaks cpu frequency scaling governor kernel module

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On Thu, 04 Jan 2024 12:37:51 +0100 Luca Boccassi <bluca@debian.org> wrote:
 > 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.
 > >


Some tips that I already have:

1. Many distros like arch or fedora have change 
CONFIG_CPU_FREQ_GOV_POWERSAVE from m to y. It is possible that they all 
have met such problem.

2. In Debian bug report I find something that may have some relation. 
See bug #1010581

3. I find that if CONFIG_CPU_FREQ_GOV_POWERSAVE=m, then though such 
module cannot be in use after boot at once, but it is possible to 
manually modprobe them. So it may indicate that to use 
CONFIG_CPU_FREQ_GOV_POWERSAVE=m with   CONFIG_MODULE_COMPRESS_XZ=y is 
actually possible. The problem we find here may be not so fundamental.


What else I want to say:

1. Changing such configs from m to y can solve the problem with almost 
not cost. So I suggest thinking about it.

2.  Surely I accept your suggestion that it is very likely a small 
mistake from kernel upstream, since even at userspace I can load and use 
these module by manually modprobe. I want to communicate with upstream 
but  I do not know how to use kernel.org bugzilla. The problem I have is 
that, I do not know how to make a line end. You can see here 
(https://bugzilla.kernel.org/show_bug.cgi?id=218341) that I use some 
stupid way to make new lines. So could you teach me how to start new 
line in kernel bugzilla?


Thanks,

Jy Deng

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Bug#1059969: linux-image-6.6.9-amd64: CONFIG_MODULE_COMPRESS_XZ=y breaks cpu frequency scaling governor kernel module Luca Boccassi <bluca@debian.org> - 2024-01-04 12:40 +0100
  Bug#1059969: linux-image-6.6.9-amd64: CONFIG_MODULE_COMPRESS_XZ=y breaks cpu frequency scaling governor kernel module Jy Deng <1700011628@pku.edu.cn> - 2024-01-04 14:50 +0100
    Bug#1059969: linux-image-6.6.9-amd64: CONFIG_MODULE_COMPRESS_XZ=y breaks cpu frequency scaling governor kernel module Diederik de Haas <didi.debian@cknow.org> - 2024-01-04 15:20 +0100
      Bug#1059969: linux-image-6.6.9-amd64: CONFIG_MODULE_COMPRESS_XZ=y breaks cpu frequency scaling governor kernel module Jy Deng <1700011628@pku.edu.cn> - 2024-01-04 16:00 +0100
      Bug#1059969: linux-image-6.6.9-amd64: CONFIG_MODULE_COMPRESS_XZ=y breaks cpu frequency scaling governor kernel module Jy Deng <1700011628@pku.edu.cn> - 2024-01-04 16:50 +0100

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